A functional neuroimaging review of obesity, appetitive hormones and ingestive behavior

Abstract

Adequate energy intake is vital for the survival of humans and is regulated by complex homeostatic and hedonic mechanisms. Supported by functional MRI (fMRI) studies that consistently demonstrate differences in brain response as a function of weight status during exposure to appetizing food stimuli, it has been posited that hedonically driven food intake contributes to weight gain and obesity maintenance. These food reward theories of obesity are reliant on the notion that the aberrant brain response to food stimuli relates directly to ingestive behavior, specifically, excess food intake. Importantly, functioning of homeostatic neuroendocrine regulators of food intake, such as leptin and ghrelin, are impacted by weight status. Thus, data from studies that evaluate the effect of weight status on brain response to food may be a result of differences in neuroendocrine functioning and/or behavior. In the present review, we examine the influence of weight and weight change, exogenous administration of appetitive hormones, and ingestive behavior on BOLD response to food stimuli.

Posttraumatic stress disorder: A metabolic disorder in disguise?

“…Corresponding functional MRI studies in obese patients show increased activation of striatal regions in response to food cues (Burger and Berner, 2014). However, these studies do not examine brain areas that are implicated in the etiology of PTSD, such as the amygdala and hippocampus, as these regions are not typically of interest to studying obesity and metabolic disease.…”

Less-than-expected weight loss in normal-weight women undergoing caloric restriction and exercise is accompanied by preservation of fat-free mass and metabolic adaptations

“…For this purpose, we retrospectively analyzed data from a randomized controlled trial that assessed the impact of caloric restriction and exercise on reproductive function. 20 Primary outcomes included body weight, body composition, RMR and metabolic hormones linked to energy conservation and future weight regain, including leptin, 16,21,22 ghrelin, 21,23 triiodothyronine (T3) 24,25 and insulin-like growth factor-1 (IGF-1). 26 We hypothesized that 3 months of caloric restriction combined with exercise would result in significant weight loss, but that exercise would preserve lean mass and promote loss of fat mass such that actual weight loss would be less than predicted.…”

Regulation of food intake and the development of anti-obesity drugs

“…Hunger hormones like Orexin and Ghrelin, or high-calorie food prompt people to eat. Satiety hormones such as leptin, insulin and other so called brain-gut peptides can inhibit feeding behavior (15). Long-term imbalance between hunger and satiety signals lead to weight increase and obesity.…”