Physical Activity and Dietary Interventions in Severe Obesity

The increase in rates of severe obesity over the past 30 years has clinically significant implications due to increased rates of comorbidity, particularly hypertension and type 2 diabetes mellitus, among those with severe obesity. African American women have had an especially high increase in the prevalence of severe obesity. With the exceptions of bariatric surgery and pharmacology, treatment of severe obesity has not been carefully studied in clinical trials to date. Researchers recently conducted a single-blind randomized trial to determine the efficacy of an intervention based on weight loss and physical activity on the adverse health risks associated with severe obesity. The trial was conducted from February 2007 through April 2010 at the University of Pittsburgh, Pennsylvania. Results were reported online in the Journal of the American Medical Association [2010; 304(16):(doi:10.1001/jama.2010.1505)]. Eligibility criteria included age 30 to 55 years and presence of severe obesity, defined as body mass index between 35 and 39.9 (weight in kilograms divided by height in meters squared) for class II obesity and ≥40 for class III obesity. Participants were required to be able to walk without assistance, commit to a schedule of intervention and assessment visits, and obtain medical clearance for intervention. Exclusion criteria included history of cancer within the past 5 years, history of or currently receiving treatment for coronary artery disease, enrollment with the past year in a formal weight reduction program, self-report of loss of >5% of current body weight within the past 6 months, history of bariatric surgery, pregnancy during the past 6 months, or uncontrolled hypertension or diabetes. The primary outcome measure was change in weight. Secondary outcome measures were components comprising cardiometabolic risk, including waist circumference, abdominal adipose tissue, and hepatic fat content. The study included a 1-year intensive lifestyle intervention focusing on diet and physical activity. The 130 study participants were randomized to 1 of 2 groups: the initial physical activity group was randomized to diet and physical activity for the 12-month study period; the delayed physical activity group had the same dietary intervention, but the physical activity intervention was delayed for 6 months. Of the randomized participants, 78% (n=101) completed the 12 months of follow-up assessments. Characteristics of the 2 groups were similar at baseline; 75% of participants had class III obesity and the proportions were similar in both groups. At 6 months, participants in both groups had lost a significant amount of weight: 10.9 kg (95% confidence interval [CI], 9.1-12.7) in the initial physical activity group versus 8.2 kg in the delayed physical activity group (95% CI, 6.4-9.9). However, participants in the initial activity group lost significantly more weight in the first 6 months compared with the delayed activity group; P=.02 for group × time interaction. At 12 months, weight loss was similar in the 2 groups: 12.1 kg (95% CI, 10.0-14.2) in the initial activity group versus 9.9 kg in the delayed activity group (95% CI, 8.0-11.7); P=.25 for group × time interaction. At both 6 and 12 months, both groups had significant reduction in body fat and waist circumference. Compared with the delayed activity group, the initial activity group had significantly greater reductions in body fat and waist circumference at 6 months. At the end of the subsequent 6 months when participants in both groups were engaged in physical activity, there were no differences in body fat or waist circumference between the groups. Loss of visceral abdominal and subcutaneous abdominal adipose tissue was significant in both groups in the first 6 months. Both groups also had a decrease in hepatic fat content; the decrease was significantly greater in the initial activity group. The researchers commented that this study is the first designed “specifically to examine the effects of an intensive lifestyle intervention on weight loss, abdominal fat, hepatic steatosis, and other cardiometabolic risk factors in persons with severe obesity. Our results indicate that this nonsurgical approach can be an effective treatment for severe obesity.”