Pilot 12-Week Weight-Loss Comparison: Low-Fat vs Low-Carbohydrate (Ketogenic) Diets

Reference:
Greene, P., Willett, W., Devecis, J., et al., "Pilot 12-Week Feeding Weight-Loss Comparison: Low-Fat vs Low-Carbohydrate (Ketogenic) Diets," Abstract Presented at The North American Association for the Study of Obesity Annual Meeting 2003, Obesity Research, 11S, 2003, page 95OR.

Greene, P.J., Devecis, J., Willett, W.C., "Effects of Low-Fat Vs Ultra-Low-Carbohydrate Weight-Loss Diets: A 12-Week Pilot Feeding Study," abstract presented at Nutrition Week 2004, February 9-12, 2004, in Las Vegas, Nevada.

Summary:

The following summarizes information presented at multiple conferences on a pilot study conducted by Greene et al. This information was written by Atkins professionals.

BACKGROUND: Some researchers claim that people only lose weight on very low carb diets due to a reduction in calorie intake.  Others have argued that very low carb diets offer a “metabolic advantage” allowing people to lose weight without restricting calories.  The objective of this study was to evaluate if people who follow very low carb diets lose weight only due to restricting calories.

METHOD: Twenty-one participants were recruited and were randomly assigned to three separate diets for 12 weeks: a low fat diet (55% carb, 15% protein, and 30% fat) and two different very low carb diets (both had 5% carb, 30% protein, and 65% fat).  The low fat (LF) diet and one of the very low carb (LC1) diets provided a total of 1500 calories a day for women and 1800 calories a day for men.  The second very low carb diet group was allowed 300 additional calories a day (1800 calories for women and 2100 calories for men).  Meals were provided during the study. 

RESULTS: After 12 weeks, all participants lost weight.  Both the very low carb groups lost more weight than the low fat group (LC1: -23 lbs, LC2: -20 lbs, and LF: -17 lbs).  The difference between the diets was not statistically significant.  More body fat was lost than lean body mass (such as muscle) or water on all the diets.  All participants lost inches from their waist and hips.  LDL, triglycerides, and total cholesterol to HDL ratio improved on the diets.  VLDL improved significantly more on the low carb diets.  BUN increased on the low carb diets only.  However, creatinine levels (a marker of kidney function) remained unchanged.

CONCLUSION: All three diets were effective in reducing weight in adults and the weight lost was primarily body fat.  Even participants consuming higher calories on the very low carb diet were able to lose more weight compared to the lower calorie, low fat diet.  The low carb diets improved several risk factors for heart disease.  The authors concluded that very low carb diets do not reduce weight only by restricting calories. 

Commentary:

The following information was written by Atkins professionals.

Individuals followed one of three diets: a low fat, calorie controlled diet (1500 calories women/1800 men), a low carb, calorie controlled diet (1500 calories women/1800 men), or a low carb diet containing 300 additional calories a day (1800 women/2100 men). Individuals following a low carb diet (5% carbohydrate, 30% protein, 65% fat) lost weight regardless of whether calories were restricted. Weight loss in both low carb groups was greater than for those following a low fat diet (55% carbohydrate, 15% protein, 30% fat). These results suggest that a low carb diet, with or without caloric restriction, produces greater weight loss than a low fat diet.

Treating the Metabolic Syndrome with Carbohydrate Restriction

Reference:
Hickey, J.T., Hickey, L., Yancy, W.S., et al., "Clinical Use of a Carbohydrate-Restricted Diet to Treat the Dyslipidemia of the Metabolic Syndrome", Metabolic Syndrome and Related Disorders, 2003, 1(3), pages 227-232.

Summary:

The following information is available from the publisher at liebertpub and was not written by Atkins professionals.

Commentary:

The following information was written by Atkins professionals.

Patients with atherogenic dyslipidemia who followed Induction for two weeks and then proceeded onto OWL had improved total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. Atherogenic dyslipidemia is a condition associated with the metabolic syndrome, which increases risk of developing type 2 diabetes and the diseases associated with atherosclerosis. Thus, controlled carbohydrate diets may decrease the risk of developing these diseases in patients with atherogenic dyslipidemia.

One Year Effectiveness of the Atkins, Ornish, Weight Watchers, and Zone Diets in Decreasing Body Weight and Heart Disease Risk

Reference:
Dansinger, M.L., Gleason, J. L., Griffith,  J.L., et al., " One Year Effectiveness of the Atkins, Ornish, Weight Watchers, and Zone Diets in Decreasing Body Weight and Heart Disease Risk,"Presented at the American Heart Association Scientific Sessions November 12,2003 in Orlando, Florida.

Summary:

The following information was a conference presentation and was not written by Atkins professionals.

OBJECTIVES: Our aim was to test the one year efficacy of four popular diet book approaches in promoting weight loss and reducing 10 year heart disease risk.

METHODS: 160 overweight or obese men and women (mean body mass index 35 kg/m2) were recruited by advertising and were randomized to either a low carbohydrate (Atkins), a low fat (Ornish), a low glycemic load (Zone), or a calorie-restricted (Weight Watchers) dietary program. Participants were given the diet books and received 4 group classes over a 2 month period taught by the same doctor and dietition. Dietary intake (3 day food record), self assessed adherence, body weight, blood pressure, glucose, insulin, plasma lipid and lipoprotein cholesterol levels, and C reactive protein were assessed after an overnight fast at baseline, 2, 6, and 12 months. The primary outcome variables were percent change in body weight and heart disease risk reduction based on the Framingham score using continuous variables.

RESULTS: For all 160 participants (n=40/group) assuming no change from baseline for dropouts, mean percent weight loss and reduction in Framingham score at 12 months were 2.1% and 6.4% for Atkins, 3.1% and 3.3% for Ornish, 3.0% and 9.6% for Weight Watchers, and 3.0% and 6.9% for Zone. For 12 month completers percent reductions in weight and risk score were 3.9% and 12.3% for Atkins (n=21, 52% completion), 6.2% and 6.6% for Ornish (n=20, 50% completion), 4.5% and 14.7% for Weight Watchers (n=26, 65% completion), and 4.6% and 10.5% for Zone (n=26, 65% completion). All diets resulted in significant (p<0.05) weight loss from baseline and all but the Ornish diet (p=0.013) resulted in significant reductions in the Framingham risk score, with either analysis, with no significant difference between diets.

CONCLUSIONS: Using very divergent approaches, all 4 popular diets promoted weight loss and heart disease risk reduction especially in adherent subjects, indicating that a variety of dietary strategies can be effective in this regard.

Commentary:

The following information was written by Atkins professionals.

Overweight and obese men and women were assigned to one of four diets: Atkins diet, Ornish diet (a very low fat diet), the Zone diet (40% carbs, 30% protein, 30% fat), or Weight Watchers (a calorie reduced diet) for one year. Dietary guidance was provided to all groups. All diets led to weight loss. Men and women who followed Atkins for one year had significant reductions in weight and lowered their risk of heart disease.

Very Low Carbohydrate Diet Improves Cholesterol and Triglyceride Levels

Reference:
Volek, J.S., Sharman, M.J., and Gomez A.L., et al., "An Isoenergetic Very Low Carbohydrate Diet Improves Serum HDL Cholesterol and Triacylglycerol Concentrations, the Total Cholesterol to HDL Cholesterol Ratio and Postprandial Lipemic Responses Compared with a Low Fat Diet in Normal Weight, Normolipidemic Women," The Journal of Nutrition, 133(9), 2003, pages 2756-2761.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Very low carbohydrate diets are popular, yet little is known about their effects on blood lipids and other cardiovascular disease risk factors. We reported previously that a very low carbohydrate diet favorably affected fasting and postprandial triacylglycerols, LDL subclasses and HDL cholesterol (HDL-C) in men but the effects in women are unclear. We compared the effects of a very low carbohydrate and a low fat diet on fasting lipids, postprandial lipemia and markers of inflammation in women. We conducted a balanced, randomized, two-period, crossover study in 10 healthy normolipidemic women who consumed both a low fat (<30% fat) and a very low carbohydrate (<10% carbohydrate) diet for 4 wk each. Two blood draws were performed on separate days at 0, 2 and 4 wk and an oral fat tolerance test was performed at baseline and after each diet period. Compared with the low fat diet, the very low carbohydrate diet increased (P </= 0.05) fasting serum total cholesterol (16%), LDL cholesterol (LDL-C) (15%) and HDL-C (33%) and decreased serum triacylglycerols (-30%), the total cholesterol to HDL ratio (-13%) and the area under the 8-h postprandial triacylglycerol curve (-31%). There were no significant changes in LDL size or markers of inflammation (C-reactive protein, interleukin-6, tumor necrosis factor-alpha) after the very low carbohydrate diet. In normal weight, normolipidemic women, a short-term very low carbohydrate diet modestly increased LDL-C, yet there were favorable effects on cardiovascular disease risk status by virtue of a relatively larger increase in HDL-C and a decrease in fasting and postprandial triaclyglycerols.

Commentary:

The following information was written by Atkins professionals.

The following information was summarized by Atkins professionals. Healthy, normal weight women with normal blood lipid profiles consuming a low carbohydrate diet lost a significant amount of weight after 4 weeks. There were significant improvements in total cholesterol, HDL cholesterol, and triglycerides after consuming the low carb diet from before the study began. These improvements were significantly greater than what was seen after the individuals consumed a low fat diet for 4 weeks. These results suggest that in the short term, a low carbohydrate diet produces weight loss with greater improvements in several heart disease risk factors compared to a low fat diet.

Glycemic Index and Glycemic Load in Endometrial Cancer

Reference:
Augustin, L.S., Gallus, S., Bosetti, C., et al., “Glycemic Index and Glycemic Load in Endometrial Cancer,” International Journal of Cancer, 105(3), 2003, pages 404-407.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Glycemic index (GI) and glycemic load (GL) are measures of the metabolic effects of dietary carbohydrates. The higher their value, the greater the glucose and insulin responses. Raised insulin levels are associated with endometrial cancer and with its risk factors including obesity, diabetes and hypertension. To study the role of the GI and GL we analyzed the data of two hospital-based case-control studies on endometrial cancer conducted between 1988-98 in Italy and Switzerland, including a total of 410 women with incident, histologically confirmed endometrial cancer and 753 controls admitted for acute, non-neoplastic diseases. A food frequency questionnaire was used to assess the subjects usual diet and to derive estimates of dietary GI and GL. The odds ratios (OR) of endometrial cancer, after adjustment for major risk factors, for the highest versus the lowest quintile of dietary GI and GL were 2.1 (95% confidence interval [CI] = 1.4-3.2) and 2.7 (95% CI = 1.8-4.2), respectively. The associations were stronger in older women, in those with higher body mass index and in hormone replacement therapy users. Our study supports the hypothesis of a direct association between GI and endometrial cancer risk

Postprandial Triglycerides in Response to High Fat: Role of Dietary Carbohydrate

Reference:
Kriketos, A.D., Campbell, L.V., Maclean, E. et al., “Postprandial Triglycerides in Response to High Fat: Role of Dietary Carbohydrate,” European Journal of Clinical Investigation, 33 (5), 2003, pages 383-389.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Background: The postprandial triglyceride response following a meal high in fat (HFM) has been related to atherogenesis and insulin resistance. We examined the influence of dietary carbohydrate and the accompanying insulin secretory response on the postprandial triglyceride response following a HFM.

Materials and design: High-fat meals of equal fat content (fat 80 g) containing either 20 g (low) or 100 g (high) of carbohydrate (HFM-LC and HFM-HC, respectively), and therefore not isocaloric (4250 kJ of HFM-LC and 5450 kJ of HFM-HC), were consumed by seven (four male, three female) normolipidaemic subjects (aged 32.9+-3.7 years, BMI 24.7+-1.8 kg m-2). Blood and indirect calorimetry data were collected at 0-4 h.

Results: HFM-HC produced a significant rise in plasma glucose (DELTA0.54+-0.23 mmol L-1, P=0.05) at 2 h, while a HFM-LC elicited no mean change from baseline. Following a HFM-LC, the plasma insulin incremental area under the curve (AUC) was significantly lower (31.3+-6.7 vs. 83.2+-11.9 mU l-1 h-1, P0.0003) and the postprandial triglyceride response AUC was significantly greater (1.66+-0.36 vs. 1.24+-0.31 mmol L-1 h-1, P<0.006) compared with a HFM-HC. Plasma free fatty acids were suppressed by 44% (P=0.04) and 66% (P<0.0001) at 1 h following HFM-LC and HFM-HC, respectively, compared with baseline. There were no significant differences between the meals in energy expenditure, substrate oxidation rates, or respiratory quotient responses.

Conclusions: By design, the HFMs were not isocaloric but the presence of carbohydrate in a HFM invoked an insulin response that significantly reduced the 4 h postprandial triglyceride response even in healthy, normolipidaemic subjects. This phenomenon may have clinical implications, particularly in relation to insulin sensitivity.  

Years of Life Lost Due to Obesity

Reference:
Fontaine, K.R., Redden, D.T., Wang, C., et al., "Years of Life Lost Due to Obesity," The Journal of the American Medical Association, 289(2), 2003, pages 187-193.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

CONTEXT: Public health officials and organizations have disseminated health messages regarding the dangers of obesity, but these have not produced the desired effect.

OBJECTIVE: To estimate the expected number of years of life lost (YLL) due to overweight and obesity across the life span of an adult.

DESIGN, SETTING, AND SUBJECTS: Data from the (1) US Life Tables (1999); (2) Third National Health and Nutrition Examination Survey (NHANES III; 1988-1994); and (3) First National Health and Nutrition Epidemiologic Follow-up Study (NHANES I and II; 1971-1992) and NHANES II Mortality Study (1976-1992) were used to derive YLL estimates for adults aged 18 to 85 years. Body mass index (BMI) integer-defined categories were used (ie, <17; 17 to <18; 18 to <19; 20 to <21; 21 to 45; or > or =45). A BMI of 24 was used as the reference category.

MAIN OUTCOME MEASURE: The difference between the number of years of life expected if an individual were obese vs not obese, which was designated YLL.

RESULTS: Marked race and sex differences were observed in estimated YLL. Among whites, a J- or U-shaped association was found between overweight or obesity and YLL. The optimal BMI (associated with the least YLL or greatest longevity) is approximately 23 to 25 for whites and 23 to 30 for blacks. For any given degree of overweight, younger adults generally had greater YLL than did older adults. The maximum YLL for white men aged 20 to 30 years with a severe level of obesity (BMI >45) is 13 and is 8 for white women. For men, this could represent a 22% reduction in expected remaining life span. Among black men and black women older than 60 years, overweight and moderate obesity were generally not associated with an increased YLL and only severe obesity resulted in YLL. However, blacks at younger ages with severe levels of obesity had a maximum YLL of 20 for men and 5 for women.

CONCLUSION: Obesity appears to lessen life expectancy markedly, especially among younger adults

A Low-Carbohydrate as Compared with a Low-Fat Diet in Severe Obesity

Reference:
Samaha, F.F., Iqbal, N., Seshadri, P., et al.,  "A Low-Carbohydrate as Compared With a Low-Fat Diet in Severe Obesity," The New England Journal of Medicine, 348(21), 2003, pages 2074-2081.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Background - The effects of a carbohydrate-restricted diet on weight loss and risk factors for atherosclerosis have been incompletely assessed.

Methods - We randomly assigned 132 severely obese subjects (including 77 blacks and 23 women) with a mean body-mass index of 43 and a high prevalence of diabetes (39 percent) or the metabolic syndrome (43 percent) to a carbohydrate-restricted (low-carbohydrate) diet or a calorie- and fat-restricted (low-fat) diet.

Results - Seventy-nine subjects completed the six-month study. An analysis including all subjects, with the last observation carried forward for those who dropped out, showed that subjects on the low-carbohydrate diet lost more weight than those on the low-fat diet (mean [±SD], –5.8±8.6 kg vs. –1.9±4.2 kg; P=0.002) and had greater decreases in triglyceride levels (mean, –20±43 percent vs. –4±31 percent; P=0.001), irrespective of the use or nonuse of hypoglycemic or lipid-lowering medications. Insulin sensitivity, measured only in subjects without diabetes, also improved more among subjects on the low-carbohydrate diet (6±9 percent vs. –3±8 percent, P=0.01). The amount of weight lost (P<0.001) and assignment to the low-carbohydrate diet (P=0.01) were independent predictors of improvement in triglyceride levels and insulin sensitivity.

Conclusions - Severely obese subjects with a high prevalence of diabetes or the metabolic syndrome lost more weight during six months on a carbohydrate-restricted diet than on a calorie- and fat-restricted diet, with a relative improvement in insulin sensitivity and triglyceride levels, even after adjustment for the amount of weight lost. This finding should be interpreted with caution, given the small magnitude of overall and between-group differences in weight loss in these markedly obese subjects and the short duration of the study. Future studies evaluating long-term cardiovascular outcomes are needed before a carbohydrate-restricted diet can be endorsed.

Commentary:

The following information was written by Atkins professionals.

Severely obese individuals were counseled to either restrict carbohydrate intake to 30 grams per day or less or to reduce fat by 30% as well as calories by 500 calories per day. The low carb group had greater weight loss and greater improvement in triglycerides compared to those instructed to reduce fat and calories. Insulin sensitivity improved more in people with type 2 diabetes following the low carb diet than the low fat diet. These results suggest that a short-term, low carb diet can benefit severely obese individuals, especially those individuals who have type 2 diabetes or the metabolic syndrome.

Randomized Trial of a Low-Carbohydrate Diet for Obesity

Reference:
Foster, G.D., Wyatt, H.R., Hill, J.O., et al., "A Randomized Trial of a Low-Carbohydrate Diet for Obesity," The New England Journal of Medicine, 348(21), 2003, pages 2082-2090.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Background: Despite the popularity of the low-carbohydrate, high-protein, high-fat (Atkins) diet, no randomized, controlled trials have evaluated its efficacy.

Methods: We conducted a one-year, multicenter, controlled trial involving 63 obese men and women who were randomly assigned to either a low-carbohydrate, high-protein, high-fat diet or a low-calorie, high-carbohydrate, low-fat (conventional) diet. Professional contact was minimal to replicate the approach used by most dieters.

Results:- Subjects on the low-carbohydrate diet had lost more weight than subjects on the conventional diet at 3 months (mean [±SD], -6.8±5.0 vs. -2.7±3.7 percent of body weight; P=0.001) and 6 months (-7.0±6.5 vs. -3.2±5.6 percent of body weight, P=0.02), but the difference at 12 months was not significant (-4.4±6.7 vs. -2.5±6.3 percent of bodyweight, P=0.26). After three months, no significant differences were found between the groups in total or low-density lipoprotein cholesterol concentrations. The increase in high-density lipoprotein cholesterol concentrations and the decrease in triglyceride concentrations were greater among subjects on the low carbohydrate diet than among those on the conventional diet throughout most of the study. Both diets significantly decreased diastolic blood pressure and the insulin response to an oral glucose load.

Conclusions: The low-carbohydrate diet produced a greater weight loss (absolute difference, approximately 4 percent) than did the conventional diet for the first six months, but the differences were not significant at one year. The low-carbohydrate diet was associated with a greater improvement in some risk factors for coronary heart disease. Adherence was poor and attrition was high in both groups. Longer and larger studies are required to determine the long-term safety and efficacy of low-carbohydrate, high-protein, high-fat diets.

Commentary:

The following information was written by Atkins professionals.

Obese men and women were instructed to follow either a low carb diet or a low fat diet for one year. Men and women on the low carb diet were instructed to read and follow Dr. Atkins’ New Diet Revolution with little professional guidance. Both groups lost weight and had improvements in blood pressure, HDL cholesterol, and triglycerides after 12 months. In fact, the low carbohydrate diet resulted in greater improvements in HDL cholesterol and triglycerides after 12 months compared to the low fat diet.

Weight Loss and Cardiovascular Risk Factors in Healthy Women on a Low Carbohydrate Diet or a Low Fat Diet

Reference:
Brehm, B.J., Seeley, R.J., Daniels, S.R., et al., "A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet on Body Weight and Cardiovascular Risk Factors in Healthy Women," The Journal of Clinical Endocrinology and Metabolism, 88(4), 2003, pages 1617-1623.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Untested alternative weight loss diets, such as very low carbohydrate diets, have unsubstantiated efficacy and the potential to adversely affect cardiovascular risk factors. Therefore, we designed a randomized, controlled trial to determine the effects of a very low carbohydrate diet on body composition and cardiovascular risk factors. Subjects were randomized to 6 months of either an ad libitum very low carbohydrate diet or a calorie-restricted diet with 30% of the calories as fat. Anthropometric and metabolic measures were assessed at baseline, 3 months, and 6 months. Fifty-three healthy, obese female volunteers (mean body mass index, 33.6 +/- 0.3 kg/m(2)) were randomized; 42 (79%) completed the trial. Women on both diets reduced calorie consumption by comparable amounts at 3 and 6 months. The very low carbohydrate diet group lost more weight (8.5 +/- 1.0 vs. 3.9 +/- 1.0 kg; P < 0.001) and more body fat (4.8 +/- 0.67 vs. 2.0 +/- 0.75 kg; P < 0.01) than the low fat diet group. Mean levels of blood pressure, lipids, fasting glucose, and insulin were within normal ranges in both groups at baseline. Although all of these parameters improved over the course of the study, there were no differences observed between the two diet groups at 3 or 6 months. beta- Hydroxybutyrate increased significantly in the very low carbohydrate group at 3 months (P = 0.001). Based on these data, a very low carbohydrate diet is more effective than a low fat diet for short-term weight loss and, over 6 months, is not associated with deleterious effects on important cardiovascular risk factors in healthy women.

Commentary:

The following information was written by Atkins professionals.

Obese women were instructed to follow either a low fat, calorie restricted diet (30% of calories from fat) or a low carb diet for six months. The low carb diet was composed of two weeks of Induction followed by OWL (average intake at end of study was 97 grams of carbs per day). The women lost significantly more weight and body fat on the low carb diet than women instructed on the low fat diet at 3 and 6 months. Additionally, blood pressure, triglycerides, cholesterol, fasting blood sugar, and insulin improved. The low carb diet was more effective than the low fat diet in achieving weight loss over a period of six months. In addition, the short-term use of the low carb diet was not associated with negative effects on heart disease risk.

Review of the Efficacy and Safety of Low-Carbohydrate Diets

Reference:
Bravata, D.M., Sanders, L., Huang, J., et al., "Efficacy and Safety of Low-Carbohydrate Diets: A Systematic Review," The Journal of the American Medical Association, 289(14), 2003, pages 1837-1850.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

CONTEXT: Low-carbohydrate diets have been popularized without detailed evidence of their efficacy or safety. The literature has no clear consensus as to what amount of carbohydrates per day constitutes a low-carbohydrate diet.

OBJECTIVE: To evaluate changes in weight, serum lipids, fasting serum glucose, and fasting serum insulin levels, and blood pressure among adults using low-carbohydrate diets in the outpatient setting.

DATA SOURCES: We performed MEDLINE and bibliographic searches for English-language studies published between January 1, 1966, and February 15, 2003, with key words such as low carbohydrate, ketogenic, and diet.

STUDY SELECTION: We included articles describing adult, outpatient recipients of low-carbohydrate diets of 4 days or more in duration and 500 kcal/d or more, and which reported both carbohydrate content and total calories consumed. Literature searches identified 2609 potentially relevant articles of low-carbohydrate diets. We included 107 articles describing 94 dietary interventions reporting data for 3268 participants; 663 participants received diets of 60 g/d or less of carbohydrates-of whom only 71 received 20 g/d or less of carbohydrates. Study variables (eg, number of participants, design of dietary evaluation), participant variables (eg, age, sex, baseline weight, fasting serum glucose level), diet variables (eg, carbohydrate content, caloric content, duration) were abstracted from each study.

DATA EXTRACTION: Two authors independently reviewed articles meeting inclusion criteria and abstracted data onto pretested abstraction forms.

DATA SYNTHESIS: The included studies were highly heterogeneous with respect to design, carbohydrate content (range, 0-901 g/d), total caloric content (range, 525-4629 kcal/d), diet duration (range, 4-365 days), and participant characteristics (eg, baseline weight range, 57-217 kg). No study evaluated diets of 60 g/d or less of carbohydrates in participants with a mean age older than 53.1 years. Only 5 studies (nonrandomized and no comparison groups) evaluated these diets for more than 90 days. Among obese patients, weight loss was associated with longer diet duration (P =.002), restriction of calorie intake (P =.03), but not with reduced carbohydrate content (P =.90). Low-carbohydrate diets had no significant adverse effect on serum lipid, fasting serum glucose, and fasting serum insulin levels, or blood pressure.

CONCLUSIONS: There is insufficient evidence to make recommendations for or against the use of low-carbohydrate diets, particularly among participants older than age 50 years, for use longer than 90 days, or for diets of 20 g/d or less of carbohydrates. Among the published studies, participant weight loss while using low-carbohydrate diets was principally associated with decreased caloric intake and increased diet duration but not with reduced carbohydrate content.

Very-Low Carbohydrate Weight-Loss Diets Revisited

Reference:
Volek, J.S., Westman, E.C., "Very-Low-Carbohydrate Weight-Loss Diets Revisited," Clevland Clinic Journal of Medicine, 69(11), 2002, pages 849-862.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Much scientific and anecdotal data demonstrate favorable metabolic responses to very-low-carbohydrate diets. We believe that very-low-carbohydrate diets merit further study for weight loss, and that criticisms of these diets lack scientific evidence.

View the entire Research Study

Commentary:

The following information was written by Atkins professionals.

A review of published research on low carb diets confirms that individuals tend to lose more weight on carbohydrate restricted diets than on conventional weight loss diets and water accounted for only a small percentage of the weight lost. Low carb diets have shown favorable effects on several risk factors associated with heart disease. Additionally, some studies have shown that very low carb diets may improve performance during endurance exercise.

Increased Dietary Protein Improves Blood Sugar and Insulin Levels During Weight Loss

Reference:
Layman, D.K., Shiue, H., Sather, C., et al., "Increased Dietary Protein Modifies Glucose and Insulin Homeostasis in Adult Women During Weight Loss," The Journal of Nutrition, 133(2),2003, pages 405-410.

Summary:

The following information is available at Pub Med and was not written by Atkins professionals.

Amino acids interact with glucose metabolism both as carbon substrates and by recycling glucose carbon via alanine and glutamine; however, the effect of protein intake on glucose homeostasis during weight loss remains unknown. This study tests the hypothesis that a moderate increase in dietary protein with a corresponding reduction of carbohydrates (CHO) stabilizes fasting and postprandial blood glucose and insulin during weight loss. Adult women (n = 24; >15% above ideal body weight) were assigned to either a Protein Group [protein: 1.6 g/(kg. d); CHO <40% of energy] or CHO Group [protein: 0.8 g/(kg. d); CHO >55%]. Diets were equal in energy (7100 kJ/d) and fat (50 g/d). After 10 wk, the Protein Group lost 7.53 +/- 1.44 kg and the CHO Group lost 6.96 +/- 1.36 kg. Plasma amino acids, glucose and insulin were determined after a 12-h fast and 2 h after a 1.67 MJ test meal containing either 39 g CHO, 33 g protein and 13 g fat (Protein Group) or 57 g CHO, 12 g protein and 14 g fat (CHO Group). After 10 wk, subjects in the CHO Group had lower fasting (4.34 +/- 0.10 vs 4.89 +/- 0.11 mmol/L) and postprandial blood glucose (3.77 +/- 0.14 vs. 4.33 +/- 0.15 mmol/L) and an elevated insulin response to meals (207 +/- 21 vs. 75 +/- 18 pmol/L). This study demonstrates that consumption of a diet with increased protein and a reduced CHO/protein ratio stabilizes blood glucose during nonabsorptive periods and reduces the postprandial insulin response.

One cheer for Atkins


by Bernadine Healy, M.D. | Jun 02 '03

It has been hailed as a "diet revolution," but in fact it's been more like a 30-year food fight. The issue is the safety and effectiveness of the high-protein, low-carbohydrate diet widely known as Atkins after its popularizer, the late physician Robert Atkins. This fast and painless way to weight loss has incited equal measures of public enthusiasm and medical scorn.

The dietary skirmish is not going to be settled anytime soon, certainly not by the two new reports in last week's New England Journal of Medicine comparing this no-pain diet with standard medical fare. The studies are important but small victories for Atkins aficionados. They indeed showed that extremely overweight people could modestly melt pounds away with no evident harm. Specifically, the diet did not cause the expected deterioration in blood cholesterol levels. Though bad cholesterol rose a bit, there was an offsetting improvement in good cholesterol and triglycerides. But--and this is a huge but--the same studies revealed a high dropout rate, and, as with other diets, many of the lost pounds were back within a year. This is important, because Atkins claimed that the speed and gustatory pleasure of mouthwatering steaks and lobster dripping in melted butter would inspire the lifelong changes that the ascetic get-used-to-hunger, low-calorie approach has never been able to do. For a nation woefully overweight and eternally in search of an easy fix, it's worth knowing what will bring closure to this feisty debate.

In addition to celebrating eggs and ribs and sour cream, Atkins demonizes carbohydrates and scorns calorie counting as a fool's pastime. In the other corner is the medically correct crowd, the legions of doctors and nutritionists upholding the conventional medical wisdom of the "healthy diet." Healthy makes no claims to being fun: Its balanced regimen of fruits, vegetables, pastas, and grain has long been the catechism of weight loss. But such puritanical slimming has lost its sway as America has grown more and more obese and science has failed to prove Atkins wrong. Let's face it: Eating all those luscious forbidden morsels as the fat melts off is devilishly seductive.

Cream or sugar? The Atkins diet is also seductive because it makes physiological sense. The usual energy source for our body is sugar. Carbs are made of sugars, and when they run short, the body automatically shifts into a new energy gear, a kind of backup generating system--called ketosis--in which fat, not sugar, becomes the primary fuel. Ketosis (so named for ketones, the byproducts of burning fat) is an abnormal metabolic state also seen in starvation and uncontrolled diabetes. In fact, ketones can kill, but the healthy body gets rid of them promptly--through the kidneys and the lungs (an unpleasant effect of the Atkins diet is called acetone breath). Ketones have a diuretic effect and thus explain the immediate and gratifying loss of pounds. The Atkins mantra that calories don't matter is still open to debate. People are actually taking in fewer calories on very low carb diets, and ketones may be curbing hunger for more.

But seduction inevitably comes with a price tag. And that's what concerns most medical skeptics. Not to put too fine a point on it, there is simply nothing healthy about ketosis or about overloading on protein and depriving the body of fruits, vegetables, and fiber, which supply essential nutrients. The Atkins diet tacitly acknowledges this by prescribing an elaborate array of supplements, including more than 60 vitamins, minerals, plant extracts, and fish oil.

Even with supplements, the Atkins diet raises medical red flags. High-protein diets are notorious for causing gout, overworking the kidneys to the point of enlargement, and predisposing them to stones. Calcium is taken from bone and lost in the urine, putting bone health at risk. The loss of cancer-reducing fiber and nutrients in fruits and vegetables is also a concern, and driving the heart to use more fat as a fuel may impair its function. Then there's the brain. To be honest, we don't have a clue here--but what we do know is that the brain is an energy hog, using more fuel per pound than any organ in the body. On top of that, it is very picky in its fuel choice. Though most organs are perfectly happy to use fat or protein, the brain requires glucose. Ketones are its only backup, and a brain running long-term on ketones has never been looked at in detail. Indeed, some on the Atkins diet complain of headaches or concentration problems.

Based on our current state of knowledge, it's fair to say that were the Atkins diet bottled as a prescription drug, it would not be allowed on the market. And, as the studies of this past week suggest, America would not be the fatter for it.

Diet With the 'Right Carbs' Seems to Boost Health
Low-glycemic-index plan is better than low-fat or low-carb diets, study says

by Steven Reinberg, HealthDay Reporter | Aug 26 '04

Popular diets such as Atkins and South Beach recommend eating low or no carbohydrates to lose weight. But not all carbs are created equal, and now evidence suggests that using the "glycemic index" may be the way to shed pounds and boost health.

Results of a new animal study found that a low-glycemic-index diet can lead to weight loss, reduce body fat, and trim risk factors for diabetes and heart disease.

The glycemic index ranks carbohydrates based on their immediate effect on blood sugar levels. Carbohydrates that break down quickly during digestion have the highest glycemic index. Carbohydrates that break down slowly, releasing sugar gradually into the blood stream, have a low glycemic index.

The theory is that the rapid increase in blood sugar makes you hungry and causes you to eat more and gain weight. Meanwhile, carbs that release their sugar more slowly keep your hunger in check.

"Contrary to popular belief, starchy foods can be broken down to sugar very quickly," said lead researcher Dr. David Ludwig, director of the Optimal Weight for Life Program at Children's Hospital Boston. "White bread, breakfast cereals, potatoes, have a very high glycemic index, whereas fruits, vegetables, nuts and legumes have a low glycemic index," he added.

According to Ludwig, previous studies in humans have suggested that low-glycemic-index diets can have important health benefits. "But these studies have had difficulty in distinguishing the effects of glycemic index from those of other dietary factors like protein and fiber," he said.

Partly for this reason, no agency in the United States recognizes the glycemic index in human nutrition, Ludwig said. The glycemic index is recognized by many other countries and by the World Health Organization, he said.

To determine the effect of a low-glycemic-index diet in a controlled setting where the diet could be tested without interference from other factors, Ludwig's team experimented with rats.

In the experiment, rats were fed a diet of 69 percent carbohydrates. Eleven rats were randomly assigned to a high-glycemic-index diet and 10 to a low-glycemic-index diet, according to the report in the Aug. 28 issue of The Lancet.

After two to four months, the researchers found that the rats given the high-glycemic-index diet had 71 percent more body fat and 8 percent less lean muscle mass, compared with rats on the low-glycemic-index diet.

In addition, the high-glycemic-index group had significantly higher blood sugar and insulin levels and higher triglyceride levels, compared with the low-glycemic-index group.

In further experiments, rats were switched from a low- to a high-glycemic-index diet. These rats had greater increases in blood sugar and insulin, compared with animals switched from a high- to low-glycemic-index diet.

"These findings suggest that low-glycemic-index diets might help prevent and treat obesity, diabetes and heart disease," Ludwig said.

A healthful diet, according to Ludwig, includes adequate protein, healthy fats and carbohydrates that have a low-glycemic-index -- such as fruits, vegetables, nuts, whole grains and legumes.

There have never been any adverse effects from a low-glycemic-index diet, Ludwig added.

"In contrast, low-fat diets can raise bad cholesterol and lower good cholesterol," he said.

"A low-glycemic-index diet is the perfect compromise between a low-fat diet and an Atkins-type, very low carbohydrate diet," Ludwig said.

Dr. Mary Vernon, a spokeswoman for Atkins Nutritionals Inc., and co-author of the Atkins Diabetes Revolution, said, "The Atkins diet doesn't say eat meat and eat a candy bar to get your carbohydrates."

Vernon said the diet recommends limiting carbohydrates to 20 grams per day until you lose the weight you want, and then increasing your intake of carbohydrates until you see that you are starting to gain weight.

"The Atkins diet recommends certain carbohydrate sources, which are all low-glycemic-index sources," Vernon said. "Carbohydrates with a low glycemic index are healthy carbs with nutritional value, not just energy value," she added.

Effects of dietary glycaemic index on adiposity, glucose homoeostasis, and plasma lipids in animals.

Pawlak DB, Kushner JA, Ludwig DS.
Lancet. 2004 Aug 28;364(9436):778-85.
Department of Medicine, Children's Hospital, Boston, MA, USA. david.ludwig@childrens.harvard.edu

BACKGROUND: Clinical studies suggest a role for dietary glycaemic index (GI) in bodyweight regulation and diabetes risk. However, partly because manipulation of GI can produce changes in potentially confounding dietary factors such as fibre content, palatability, and energy density, its relevance to human health remains controversial. This study examined the independent effects of GI in animals. METHODS: Partially pancreatectomised male Sprague-Dawley rats were given diets with identical nutrients, except for the type of starch: high-GI (n=11) or low-GI (n=10). The animals were fed in a controlled way to maintain the same mean bodyweight in the two groups for 18 weeks. Further experiments examined the effects of GI in rats in a cross-over design and C57BL/6J mice in a parallel design. FINDINGS: Despite having similar mean bodyweight (547.9 [SE 13.4] vs 549.2 [15.2] g), rats given high-GI food had more body fat (97.8 [13.6] vs 57.3 [7.2] g; p=0.0152) and less lean body mass (450.1 [9.6] vs 491.9 [11.7] g; p=0.0120) than those given low-GI food. The high-GI group also had greater increases over time in the areas under the curve for blood glucose and plasma insulin after oral glucose, lower plasma adiponectin concentrations, higher plasma triglyceride concentrations, and severe disruption of islet-cell architecture. Mice on the high-GI diet had almost twice the body fat of those on the low-GI diet after 9 weeks. INTERPRETATION: These findings provide a mechanistic basis for interpretation of studies of GI in human beings. RELEVANCE TO PRACTICE: The term GI describes how a food, meal, or diet affects blood sugar during the postprandial period. GI as an independent factor can cause obesity and increase risks of diabetes and heart disease in animals. Use of low-GI diets in prevention and treatment of human disease merits thorough examination.

Lancet. 2004 Jul 17;364(9430):257-62

Association between child and adolescent television viewing and adult health: a longitudinal birth cohort study.

Hancox RJ, Milne BJ, Poulton R.

Dunedin Multidisciplinary Health and Development Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 913, Dunedin New Zealand. bob.hancox@dmhdru.otago.ac.nz

BACKGROUND: Watching television in childhood and adolescence has been linked to adverse health indicators including obesity, poor fitness, smoking, and raised cholesterol. However, there have been no longitudinal studies of childhood viewing and adult health. We explored these associations in a birth cohort followed up to age 26 years. METHODS: We assessed approximately 1000 unselected individuals born in Dunedin, New Zealand, in 1972-73 at regular intervals up to age 26 years. We used regression analysis to investigate the associations between earlier television viewing and body-mass index, cardiorespiratory fitness (maximum aerobic power assessed by a submaximal cycling test), serum cholesterol, smoking status, and blood pressure at age 26 years. FINDINGS: Average weeknight viewing between ages 5 and 15 years was associated with higher body-mass indices (p=0.0013), lower cardiorespiratory fitness (p=0.0003), increased cigarette smoking (p<0.0001), and raised serum cholesterol (p=0.0037). Childhood and adolescent viewing had no significant association with blood pressure. These associations persisted after adjustment for potential confounding factors such as childhood socioeconomic status, body-mass index at age 5 years, parental body-mass index, parental smoking, and physical activity at age 15 years. In 26-year-olds, population-attributable fractions indicate that 17% of overweight, 15% of raised serum cholesterol, 17% of smoking, and 15% of poor fitness can be attributed to watching television for more than 2 h a day during childhood and adolescence. INTERPRETATION: Television viewing in childhood and adolescence is associated with overweight, poor fitness, smoking, and raised cholesterol in adulthood. Excessive viewing might have long-lasting adverse effects on health.

Commentary

Glycemic Load Comes of Age

David S. Ludwig¹

Department of Medicine, Children’s Hospital, Boston, MA 02115

¹To whom correspondence should be addressed. E-mail: david.ludwig@tch.harvard.edu.

See related article: J. Nutr. 133: 2728-2732, 2003.

Diet can be categorized according to a great number of biological and physicochemical properties. A key challenge in the formulation of nutritional recommendations is to identify which of these properties have the greatest relevance to health promotion and disease prevention. An article in the current issue of The Journal of Nutrition addresses this issue in relation to dietary carbohydrate (1).

With the recent recognition of the physiological importance of postprandial hyperglycemia, renewed attention has been focused on carbohydrate, the only nutrient that directly alters blood glucose concentration. For individuals with diabetes, postprandial blood glucose may influence metabolic control and risk for complications more strongly than does fasting blood glucose (2). For individuals without diabetes, even moderate elevations in postprandial blood glucose can place metabolic and oxidative stress on the pancreatic B-cell and the cardiovascular system, potentially increasing risk for type 2 diabetes and heart disease (3,4). Therefore, it is of particular interest to quantify the effects of dietary carbohydrate on the glycemic response to food.

Throughout much of the last century, carbohydrate was classified as complex or simple in the belief that saccharide chain length determines the rates of digestion and absorption (5). However, many starchy foods raise blood glucose as much as or more than comparable amounts of table sugar, leading David Jenkins and colleagues at the University of Toronto to propose the concept of glycemic index (GI) in 1981 (6). GI refers to the effect of standard amounts of individual foods (containing 50 g of available carbohydrate) on blood glucose compared with that of a control food. Most of the foods at the base of the USDA’s Food Guide Pyramid (bread, breakfast cereals and rice) and potato products are rapidly hydrolyzed into glucose in the human digestive tract and therefore have a high GI, whereas nonstarchy vegetables, fruits, legumes and nuts generally have a low GI (7). Because foods and meals differ in carbohydrate content, Walter Willett and colleagues at Harvard defined the glycemic load (GL) in 1997 as the arithmetic product of GI and carbohydrate amount (8).

To date, 15 epidemiological studies have examined the relationship between GL and chronic diseases (8–22). GL is associated with several cardiovascular disease risk factors, including low HDL cholesterol (12,14), high triglycerides (14) and elevated C-reactive protein (15). GL appears to be an independent risk factor for myocardial infarction (10), type 2 diabetes (8,9) and cancer (11,13,16,17,19,20) in many but not all analyses (18,21,22). Several recent reviews have explored the physiological mechanisms that might link GL to disease processes (23–26).

Though endorsed by many official health agencies around the world, the principles underlying GL have not been recognized by any governmental or professional entity in the United States. The American Diabetes Association, in a recent review of existing evidence, concluded that glycemic responses to foods may differ, but that "the total amount of carbohydrate in meals and snacks is more important than the source or type" (27). Another concern is that GL, a mathematical concept, has not been physiologically validated as a reliable measure of glycemic response.

To address this controversy, Jennie Brand-Miller at the University of Sydney and colleagues conducted two feeding studies involving healthy young adults (1). In the first study, subjects were given 10 different foods, each calculated to have a GL equal to a serving of white bread, but among which GI and carbohydrate amounts varied threefold. For 9 of these foods, the measured area under the glucose-over-time curve was not different from that for white bread. In the second study, subjects consumed 8 foods, again with different GI and carbohydrate amounts. Each food was consumed in portion sizes calculated to have the GL of 1, 2, 3, 4 or 6 servings of white bread. Incremental increases in GL produced step-wise increases in measured area under the glucose and insulin curves. These results demonstrate that calculated GL can predict the glycemic response to individual foods across a wide range of portion sizes, and call into question the conventional strategy of "carbohydrate counting" for controlling blood glucose levels. GL would seem to be a much better predictor than carbohydrate amount alone, because similar glycemic responses were observed among foods differing in available carbohydrate by more than twofold. This finding is consistent with Wolever and Bolognesi (28) who fed subjects 5 mixed meals of varying macronutrient composition and concluded that both GI and carbohydrate amount are necessary to explain most of the observed variability in glycemic response.

Two study limitations should be noted. First, applicability of these findings to populations at greatest risk for diseases associated with insulin resistance (the obese, the elderly, certain racial/ethnic groups and individuals with diabetes) is not known. Second, these experiments involved individual foods; the ability of GL to predict blood glucose response to mixed meals remains to be determined. However, on both points, a study by Wolever and Mehling provides reassurance (29). They randomly assigned subjects with impaired glucose tolerance to a high carbohydrate/high GI control diet or to one of two experimental diets in which GL was reduced by decreasing either total carbohydrate or GI. After 4 mo, mean plasma glucose concentrations over 8 h were lowered by the same amount (0.35 mmol/L) on the low carbohydrate and low GI diets compared with controls.

The ultimate relevance of GL depends upon whether this dietary factor independently predicts disease risk in well-controlled epidemiological studies, and whether incorporation of GL principles into interventional studies produces significant improvements in clinical endpoints. Regarding the first point, as discussed above, a growing number of studies have found associations between GL and important health outcomes that are independent of, and stronger than, those for carbohydrate amount. Regarding the second point, no large scale long-term interventional studies have yet examined GL as a primary aim. However, recent reports of greater weight loss, improved cardiovascular disease risk factors and increased insulin sensitivity on very low carbohydrate (thus, low GL) diets compared with low fat diets may be relevant (30). Such diets might promote satiety and facilitate a negative energy balance by reducing postprandial glucose and insulin responses, as previously discussed with respect to GI and GL (23,25). Nevertheless, in the longest of these studies, substantial weight regain occurred on the very low carbohydrate diet at 1 y, suggesting that subjects eventually have difficulty following such severely restrictive prescriptions. Alternatively, one might lower GL in a much less restrictive fashion with moderate reductions in total carbohydrate and GI; a 30% decrease in both would produce a 51% reduction in GL (1 - 0.7 x 0.7). Along these lines, we recently conducted a pilot study with 16 obese adolescents who were randomly assigned to an ad libitum reduced GL or an energy-restricted reduced fat diet (31). Subjects in both groups made the intended dietary changes in response to outpatient counseling, but only those on the reduced GL diet lost a significant amount of weight after 12 mo. Of particular interest, no weight regain occurred in the reduced GL group between 6 and 12 mo. Thus, low GI/GL diets may constitute an optimal compromise between low fat diets on one hand, and very low carbohydrate diets on the other.

Finally, it is worth noting that two modifications of the Food Guide Pyramid could produce significant reductions in GL and also advance other nutritional goals: moving highly processed grain products and potatoes closer to the apex; and placing nonstarchy vegetables, legumes and fruit at the base.

Manuscript received 27 June 2003. Revision accepted 2 July 2003.