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Obesity Management and Prevention: More Questions Than Answers.

More than one-third (34.9%) of the US population is obese,1 so it is critical to disseminate effective interventions to tackle this epidemic. Numerous weight management studies have been conducted, but the results have been mixed and interventions are often multifaceted, making it difficult to determine whether specific intervention characteristics, such as behavioral techniques, number of sessions, or delivery mode, lead to greater weight loss.2 Two articles in this issue of JAMA Internal Medicine3,4 test interventions that share novel attributes and raise some interesting questions about the future of obesity management and prevention. The first report by Wing and colleagues3 is a randomized clinical trial to compare 2 self-regulation interventions of varying intensities vs control in reducing weight gain among young adults over 3 years of follow-up. The study included 599 participants, mostly women (78%) with a mean age 27.7 years (range, 18-35) and mean body mass index (BMI) 25.4 (range, 21-30; calculated as weight in kilograms divided by height in meters squared). Participants were randomized to either the self-regulation plus small changes (n = 200), focused on small changes in both diet and physical activity to yield a 100kcal/d deficit, the self-regulation plus large changes (n = 197), focused on a 500to 1000-kcal/d deficit and 250 minutes of moderate physical activity per week to yield a 2.3to 4.5-kg weight loss, or control (n = 202). The small and large change interventions were delivered via 10 in-person group sessions over 4 months (average attendance was 86.0% and 87.4%, respectively) and then 4-week online refresher courses during each follow-up year. The authors found that small changes significantly reduced weight gain compared with control (−0.56 vs +0.26 kg, P < .02), but the large changes were most effective (−2.37 kg vs −0.56 kg, P < .001) and was the only arm to significantly reduce the proportion of participants gaining more than 0.45 kg (P < .05). This study has several strengths, including the 3-year follow-up with low attrition, the 3-arm design allowing a comparison of varying intervention intensity levels, and the inclusion of fidelity assessments to ensure that interventions were delivered as designed. The collection of several process measures, including changes in calorie deficit, activity levels, and frequency of self-weighing, were important to include but primarily relied on self-report. Most of the participants were women recruited through mass mailings/emails who then had to complete screening and baseline assessment visits, so limitations may include generalizability and possible selection effects. The second report by Martin and colleagues4 is a randomized clinical trial performed to test the effect of calorie restriction (CR) on mood, quality of life, sleep, and sexual function over 2 years. Using a 2:1 allocation, the authors randomized 218 healthy adults, most of whom were women (69.7%) with mean age of 37.9 years and BMI 25.1, to either 25% CR (n = 145) or ad libitum (AL) control (n = 75). The CR intervention included all meals for the first 28 days, primarily relied on intensive and individualized counseling by psychologists and nutritionists, and also included group sessions.5 Self-report questionnaires were conducted at baseline, 12 months, and 24 months. Among male participants (66 [30.3%]), reproductive hormones, including sex hormone binding globin, free testosterone, total testosterone, luteinizing hormone, and follicle-stimulating hormone, were also evaluated at baseline, 12 months, and 24 months. Martin and colleagues found that CR led to significantly greater weight loss at 24 months compared with AL (−7.6 vs 0.4 kg; P < .001). At 24 months, the CR group reported significantly improved mood, general health, sexual drive and relationship, as well as reduced tension. Compared with the AL group, sleep duration in the CR group was significantly improved at 12 months but not 24 months. Free testosterone levels decreased at 12 but not 24 months (between-group difference, −2.98 ng/dL; 95% CI, −4.75 to −1.21 ng/dL [to convert to nanomoles per liter, multiply by 0.0347]; effect size, −0.92) and sex hormone binding globulin increased in the CR group compared with the AL group at 12 months (between-group difference, 0.76; 95% CI, 0.40-1.12 μg/mL; effect size, 1.16) and 24 months (between-group difference, 0.92; 95% CI, 0.581.26 μg/mL [to convert to nanomoles per liter, multiply by 8.896]; effect size, 1.49), but total testosterone, luteinizing hormone, and follicle-stimulating hormone levels did not differ significantly between the groups. Strengths of this study include the intent-to-treat analytic approach, use of several validated questionnaires to examine patient-centered outcomes, and the 2-year follow-up. The inclusion of hormone assessments was novel but limited to male participants and when laboratory variability can still be an issue (ie, serum testosterone levels are prone to temporal and age-related variations over time). As with the first study, participants were mostly women recruited through mass mailings/emails, so limitations may include generalizability and possible selection effects. Taken together, these 2 reports3,4 enhance our understanding of possible drivers of weight loss and propose additional angles with which to tackle the growing obesity epidemic. Both reports focused on younger, healthier adults, many of whom were of normal BMI, suggesting that weight loss interventions that buffer against possible weight gain may play an important role in the growing obesity epidemic. This approach would be akin to the primary prevention of many other chronic diseases, which is standard of care. A great deal of progRelated articles Obesity Management and Prevention Invited Commentary