Abstract
Objective: To examine the psychological processes that occur whilst people are taking obesity medication orlistat and to assess longer term changes in weight, beliefs and behaviour over an 18 month period. Background: Orlistat functions by reducing fat absorption. Research indicates that orlistat can have a significant impact on weight loss however there is some variability in outcomes and it is still not clear where the variability arises from. Method: A questionnaire was completed at baseline (n=1582), 6 (n=572), 12 (n=443) and 18 months (n=519) to explore predictors of change in weight, beliefs and behaviour. The data was analysed at baseline (n=1582), 0 to 6 months. (n=572), 0 to 18 months (n=519) and the process of change over the 18 months (n=296). 10 individuals who failed to lose weight after 18 months were interviewed. The qualitative data was analysed using IPA to examine participants' explanations for their weight loss failure. Results: The results show a significant decline in weight over the first 6 months (4.5kg), then a gradual regain. Successful weight loss was related to significant event motivations, adhering to orlistat, eating less fat and greater perceived control over their weight. Orlistat functioned by educating them in what foods should not be eaten through the side effects and showed them that their weight could be controlled. To reduce failure, people needed to have a shift in identity towards someone who no longer expected to fail and to endorse the efficacy of their current method of weight loss whilst overcoming barriers. Conclusion: Successful weight loss was related to a significant event motivation and believing their weight is controllable. The additional impact of orlistat is that it promotes healthy eating and shows their weight can be controlled, which facilitates long term weight loss and maintenance.