Vertical sleeve gastrectomy in adolescents reduces the appetitive reward value of a sweet and fatty reinforcer in a progressive ratio task

Abstract

BackgroundAdolescent obesity is challenging to treat even if good multidisciplinary approaches are started early. Vertical sleeve gastrectomy (VSG) is an effective intervention for long-term weight loss, but the underlying mechanisms that result in reduced calorie intake are controversial. Anecdotal evidence from the clinic and evidence in rodents after VSG suggest a decrease in the reward value of high-calorie dense foods. ObjectivesTo determine changes in appetitive behavior of candies (high in sugar and fat) after VSG in adolescents with obesity. SettingUniversity hospital. MethodsSixteen adolescents with obesity (age 15.3 ± .5 yr) who had VSG and 10 control patients (age 13.8 ± .6 yr) who had not undergone surgery were studied. Both groups completed a progressive ratio task by clicking a computer mouse on a progressive ratio schedule to receive a candy high in sugar and fat. In the task, patients were required to expend an increasing amount of effort to obtain the reinforcer until they reach a breakpoint (measure of the reward value of the reinforcer). The task was performed before VSG and 12 and 52 weeks after VSG. ResultsThe VSG group's bodyweight decreased from the baseline 136.6 ± 5.1 to 110.9 ± 5.2 to 87.4 ± 3.7 kg after 12 and 52 weeks, respectively (P < .001). The median breakpoint for candies decreased after VSG from the baseline 320 (160–640) to 80 (50–320) to 160 (80–560) after 12 and 52 weeks, respectively (P = .01). Breakpoints for the control patients did not change (480 [160–640] versus 640 [280–640], P = .17). ConclusionVSG resulted in a reduction in the reward value of a candy, as suggested by the reduced amount of effort adolescents were prepared to expend to obtain the high-sugar and high-fat candy. The effect was most pronounced 12 weeks after surgery but was largely maintained at 1 year. Long-term attenuation of appetitive behavior may be the key to weight loss and weight loss maintenance after VSG in adolescents.