Health, pleasure, and fullness: changing mindset affects brain responses and portion size selection in adults with overweight and obesity.

Abstract

Increased portion size is an essential contributor to the current obesity epidemic. The decision of how much to eat before a meal begins (i.e. pre-meal planning), and the attention assigned to this task, plays a vital role in our portion control. We investigated whether pre-meal planning can be influenced by a shift in mindset in individuals with overweight and obesity in order to influence portion size selection and brain activity. We investigated the neural underpinnings of pre-meal planning in 36 adults of different weight groups (BMI < 25 kg/m2 and BMI ≥ 25 kg/m2) by means of functional magnetic resonance imaging. To examine the important role of attentional focus, participants were instructed to focus their mindset on the health effects of food, expected pleasure, or their intention to stay full until dinnertime, while choosing their portion size for lunch. We observed that participants of all weight groups reduced their portion size when adopting a health mindset, which was accompanied by enhanced activation of the self-control network (i.e. left prefrontal cortex). Fullness and pleasure mindsets resulted in contrasting reward responses in individuals with overweight and obesity compared to normal-weight individuals. Under the pleasure mindset, persons with overweight and obesity showed heightened activity in parts of the taste cortex (i.e. right frontal operculum), while the fullness mindset caused reduced activation in the ventral striatum, an important component of the reward system. Moreover, participants with overweight and obesity did not modify their behaviour under the pleasure mindset and selected larger portions than the normal-weight group. We were able to identify specific brain response patterns as participants made a final choice of a portion size. The results demonstrate that different brain responses and behaviours during pre-meal planning can inform the development of effective strategies for healthy weight management.