Context: Although commercial weight loss programs provide treatment to millions of clients, their efficacy has not been evaluated in rigorous long-term trials.Objective: To compare weight loss and health benefits achieved and maintained through self-help weight loss vs with a structured commercial program.Design and Setting: A 2-year, multicenter randomized clinical trial with clinic visits at 12, 26, 52, 78, and 104 weeks conducted at 6 academic research centers in the United States between January 1998 and January 2001.Participants: Overweight and obese men (n = 65) and women (n = 358) (body mass index, 27-40) aged 18 to 65 years.Intervention: Random assignment to either a self-help program (n = 212) consisting of two 20-minute counseling sessions with a nutritionist and provision of self-help resources or to a commercial weight loss program (n = 211) consisting of a food plan, an activity plan, and a cognitive restructuring behavior modification plan, delivered at weekly meetings.Main Outcome Measures: Weight change was the primary outcome measure. Secondary outcomes included waist circumference, body mass index, blood pressure, serum lipids, glucose, and insulin levels.Results: At 2 years, 150 participants (71%) in the commercial group and 159 (75%) in the self-help group completed the study. In the intent-to-treat analysis, mean (SD) weight loss of participants in the commercial group was greater than in the self-help group at 1 year (−4.3 [6.1] kg vs −1.3 [6.1] kg, respectively; P<.001) and at 2 years (−2.9 [6.5] kg vs −0.2 [6.5] kg, respectively; P<.001). Waist circumference (P = .003) and body mass index (P<.001) decreased more in the commercial group. Changes in blood pressure, lipids, glucose, and insulin levels were related to changes in weight in both groups, but between-group differences in biological parameters were mainly nonsignificant by year 2.Conclusion: The structured commercial weight loss program provided modest weight loss but more than self-help over a 2-year period.

Abnormal distribution of plasma fatty acids and increased inflammation are prominent features of metabolic syndrome. We tested whether these components of metabolic syndrome, like dyslipidemia and glycemia, are responsive to carbohydrate restriction. Overweight men and women with atherogenic dyslipidemia consumed ad libitum diets very low in carbohydrate (VLCKD) (1504 kcal:%CHO:fat:protein = 12:59:28) or low in fat (LFD) (1478 kcal:%CHO:fat:protein = 56:24:20) for 12 weeks. In comparison to the LFD, the VLCKD resulted in an increased proportion of serum total n‐6 PUFA, mainly attributed to a marked increase in arachidonate (20:4n‐6), while its biosynthetic metabolic intermediates were decreased. The n‐6/n‐3 and arachidonic/eicosapentaenoic acid ratio also increased sharply. Total saturated fatty acids and 16:1n‐7 were consistently decreased following the VLCKD. Both diets significantly decreased the concentration of several serum inflammatory markers, but there was an overall greater anti‐inflammatory effect associated with the VLCKD, as evidenced by greater decreases in TNF‐α, IL‐6, IL‐8, MCP‐1, E‐selectin, I‐CAM, and PAI‐1. Increased 20:4n‐6 and the ratios of 20:4n‐6/20:5n‐3 and n‐6/n‐3 are commonly viewed as pro‐inflammatory, but unexpectedly were consistently inversely associated with responses in inflammatory proteins. In summary, a very low carbohydrate diet resulted in profound alterations in fatty acid composition and reduced inflammation compared to a low fat diet.

The persistence of an epidemic of obesity and type 2 diabetes suggests that new nutritional strategies are needed if the epidemic is to be overcome. A promising nutritional approach suggested by this thematic review is carbohydrate restriction. Recent studies show that, under conditions of carbohydrate restriction, fuel sources shift from glucose and fatty acids to fatty acids and ketones, and that ad libitum–fed carbohydrate-restricted diets lead to appetite reduction, weight loss, and improvement in surrogate markers of cardiovascular disease.

Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations. Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses. One group habitually consumed a traditional high-carbohydrate (HC: n=10, %carbohydrate:protein:fat=59:14:25) diet, and the other a low-carbohydrate (LC; n=10, 10:19:70) diet for an average of 20 months (range 9 to 36 months). Peak fat oxidation was 2.3-fold higher in the LC group (1.54±0.18 vs 0.67±0.14 g/min; P=0.000) and it occurred at a higher percentage of VO2max (70.3±6.3 vs 54.9±7.8%; P=0.000). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21±0.02 vs 0.76±0.11 g/min; P=0.000) corresponding to a greater relative contribution of fat (88±2 vs 56±8%; P=0.000). Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (-64% from pre-exercise) and 120 min of recovery (-36% from pre-exercise). Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar.