OBJECTIVES: Weight gain is a common side effect of many therapies for type 2 diabetes (T2DM). This study reviews the medical literature to summarize the consequences of weight gain on health-related quality of life. METHODS: A review of the medical literature, including MEDLINE, EMBASE, PsycINFO, and abstracts from professional conferences, was conducted to identify studies assessing the impact of body weight on patient utility. Similarities and differences in study methodology and results were evaluated. RESULTS: Seventeen papers presented either: a) utility values by BMI or body weight or b) the change in utility scores or QALYs based on unit changes in BMI or body weight. Regardless of the patient population or methodology used to elicit utility scores, all studies reviewed found as body weight increased, patient utility decreased. Utility scores obtained using standard gamble techniques were generally higher than those using Time Trade Off or the EQ-5D. Most studies evaluated utility scores stratified by body weight or BMI and used regression analyses to attribute the difference in utility scores to differences in weight while controlling for other factors. Two studies used standard gamble methodology to evaluate the change in utility scores by asking patients to evaluate the impact of specific amounts of weight gain or loss. Studies generally assumed a constant change in utility occurs with a one unit change in BMI. However, recent studies demonstrate the magnitude of changes in utility scores may vary depending on: a) whether a patient is valuing weight loss or gain; b) whether a smaller or larger change in body weight is being evaluated; and c) baseline BMI. CONCLUSIONS: Various utility values associated with body weight using different methodologies have been published. Careful consideration should be given to determine the most appropriate utility values to use in cost utility analyses of T2DM therapies.