Differences in Weight Loss Across Different BMI Classes:A Meta-analysis of the Effects of Interventions with Diet and Exercise

Lifestyle interventions are effective for weight loss and are recommended for persons with a body mass index (BMI) of 25-40 kg m(-2). However, this group is very heterogeneous, which could influence outcomes from lifestyle interventions. In this systematic review, differences in 1-year weight change and percentage weight change after lifestyle interventions were investigated for participants varying in initial BMI using meta-analyses. Twenty-two interventions with healthy Caucasian adults, a mean BMI between 25 and 40 kg m(-2), a dietary as well as a physical activity component aiming at weight loss, and at least five contact sessions guided by a professional health care provider were selected from a systematic search in the MEDLINE database. Participants in each intervention were divided into one of the three BMI classes: overweight (BMI of 25-29.99 kg m(-2)), class-I obesity (BMI of 30-34.99 kg m(-2)), and class-II obesity (BMI of 35-39.99 kg m(-2)). Differences in weight change and percentage weight change were analyzed and compared among different BMI classes within the same intervention by calculating standardized mean differences. Overweight participants lost 1.1 kg less (p < 0.01) than participants with class-I obesity and 1.5 kg less (p < 0.01) than participants with class-II obesity. For percentage weight change, no significant differences were found among the BMI classes. Average weight change during lifestyle interventions only differs to a small extent among people with BMI between 25 and 40 kg m(-2). This implies that these interventions are equally appropriate for these BMI classes.