Background: The World Health Organization defines obesity as a body mass index of 30 kg per m² or greater, which puts almost 25 percent of the population of England in that category. Because obesity is associated with several chronic medical conditions, primary care physicians are charged with diagnosing obesity and offering clinical treatment, or recommending a commercial weight-management program. It is unclear, however, which approach or available commercial program is most effective for weight loss. Previous studies indicate that access to prolonged treatment plans (up to two years) yields greater weight loss compared with a control group, but most patients do not have access to long-term weight-management treatment. Jolly and colleagues compared the effectiveness of short-term programs for weight loss, including several commercial programs and primary care management, with a minimal-intervention control group.

The Study: Patients with obesity were recruited from 17 general practices in a regional National Health Service Trust in Great Britain. Pregnant women and those unable to understand English were excluded. Participants were randomized to one of eight groups. Three groups were assigned to commercially available weight-loss programs: Weight Watchers, Slimming World, and Rosemary Conley. Another three groups were assigned to programs provided by the National Health Service: a group weight-loss program (Size Down), one-on-one weight-loss counseling with a primary care nurse, and one-on-one weight-loss counseling with a pharmacist. Participants in the seventh group could choose which plan to participate in. Those in the eighth group (i.e., the control group) were given vouchers for 12 visits to a local gym, but did not receive any specific nutrition or weight-loss advice.

Baseline weights and heights were collected at participants' first visit to their assigned program. The primary outcome was weight loss at three months, with secondary outcomes of self-reported physical activity, weight loss at one year, and percentage weight loss at three months and at one year. Weight was recorded at the final visit for those who participated throughout the entire program; weights were collected in the office or by self-report for those who did not complete the 12-week program. At the one-year assessment, participants were interviewed about their impressions of the program to which they had been assigned and whether they had tried any other weight-loss programs over the year.

Results: To detect a 2-kg (4.44-lb) weight loss at three months with adequate power, 100 people were randomized to each of the three commercial program groups, the Slim Down group, the free-choice group, and control group. Because of limited availability, only 70 participants were randomized to the primary care and pharmacy groups. The 2-kg difference was selected because it was achievable in 12 weeks and contributed to a clinically meaningful 5 percent weight loss.

Although all groups lost some weight at three months, only participants in the Weight Watchers and Rosemary Conley groups had significantly greater weight loss and percentage weight loss than the control group (2.41 kg [5.36 lb] and 2.22 kg [4.93 lb], respectively). The least effective strategy was counseling provided by a primary care nurse. At one year, only participants in the Weight Watchers group had statistically significant weight loss compared with the control group (2.38 kg [5.29 lb]). Respondents who reported using the same weight-loss techniques they learned in the three-month study period throughout the year lost a small amount of weight at one year (0.57 kg [1.27 lb]), whereas those who changed to another method or stopped trying to lose weight gained weight at one year (1.18 kg [2.62 lb]). There was no difference in weight loss between participants randomized to a particular plan and those who were allowed to select a program.

Conclusion: In patients with obesity in a primary care population, participation for three months in select commercial weight-loss programs contributed to significant weight loss at one year. Individual weight-loss counseling through specially trained primary care practices was not effective for weight loss.