Motivational predictors of weight loss and weight-loss maintenance.

Self-determination theory proposes that behavior change will occur and persist if it is autonomously motivated.Autonomous motivation for a behavior is theorized to be a function both of individual differences in the autonomy orientation from the General Causality Orientations Scale and of the degree of autonomy supportiveness of relevant social contexts.We tested the theory with 128 patients in a 6-month, very-low-calorie weight-loss program with a 23-month follow-up.Analyses confirmed the predictions that (a) participants whose motivation for weight loss was more autonomous would attend the program more regularly, lose more weight during the program, and evidence greater maintained weight loss at follow-up, and (b) participants' autonomous motivation for weight loss would be predicted both by their autonomy orientation and by the perceived autonomy supportiveness of the interpersonal climate created by the health-care staff.Recent statistics indicate that more than 12 million American adults are severely obese and face significant health risks due to their weight (Kissebah, Freedman, & Peiris, 1989;Kuczmarski, 1992).~ In addition to being linked to heart disease, hypertension, diabetes, and various other illnesses, severe obesity has been found, in both longitudinal and actuarial studies, to significantly increase the risk of premature death (Drenick, Bale, & Seizer, 1980;Pi-Sunyer, 1993; Simopoulos & Van Itallie, 1984).Furthermore, in many countries, including the United States, obesity is a stigmatizing condition, especially for women (Sobal & Stunkard, 1989), and is often associated with dysphoric states and psychological problems.Although there is disagreement about whether or not there are significant risks associated with mild obesity (Garner & Wooley, 1991 ), there is little doubt about the seriousness of the risks associated with severe and morbid obesity. 2 Consequently, very-low-calorie diets have often been recommended for the severely or morbidly obese.Although such diets can have negative side effects (e.g., Apfelbaum, Fricker, & Igoin-Apfelbaum, 1987), the risks related to severe and morbid obesity are believed to outweigh those related to the diets.Typically, people who persist at very-low-calorie diets lose large amounts of weight, averaging about 44 lbs (20 kg) in 12-16 weeks (Wadden, 1993).The great majority of these individuals, however, regain a substantial portion of that weight within