Highlights d We performed functional MRI in individuals who undertook a weight-loss regimen d Calorie restriction led to weight loss and leptin and ghrelin adaptations d We uncovered a neural signature of successful weight loss d The best predictor of success was activation in prefrontal cortex during the regime
Psychosocial stress is associated with an increased intake of palatable foods and weight gain in stress-reactive individuals. Personality traits have been shown to predict stress-reactivity. However, it is not known if personality traits influence brain activity in regions implicated in appetite control during psychosocial stress. The current study assessed whether Gray's Behavioural Inhibition System (BIS) scale, a measure of stress-reactivity, was related to the activity of brain regions implicated in appetite control during a stressful period. Twenty-two undergraduate students participated in a functional magnetic resonance imaging (fMRI) experiment once during a non-exam period and once during final exams in a counter-balanced order. In the scanner, they viewed food and scenery pictures. In the exam compared with the non-exam condition, BIS scores related to increased perceived stress and correlated with increased blood-oxygen-level dependent (BOLD) response to high-calorie food images in regions implicated in food reward and subjective value, such as the ventromedial prefrontal cortex, (vmPFC) and the amygdala. BIS scores negatively related to the functional connectivity between the vmPFC and the dorsolateral prefrontal cortex. The results demonstrate that the BIS trait influences stress reactivity. This is observed both as an increased activity in brain regions implicated in computing the value of food cues and decreased connectivity of these regions to prefrontal regions implicated in self-control. This suggests that the effects of real life stress on appetitive brain function and self-control is modulated by a personality trait. This may help to explain why stressful periods can lead to overeating in vulnerable individuals.
Summary 22Insufficient responses to hypocaloric diets have been attributed to hormonal adaptations that 23 override self-control of food intake. We tested this hypothesis by measuring brain fMRI reactivity 24 to food cues and circulating energy-balance hormones in 24 overweight/obese participants before, 25 and 1 and 3 months after starting a calorie restriction diet. Increased activity in prefrontal regions at 26 month 1 correlated with weight loss at months 1 and 3. Weight loss was also correlated with 27 increased plasma ghrelin and decreased leptin at month 1, and these changes were associated with 28 greater food cue reactivity in reward-related brain regions. However, the reduction in leptin did not 29 counteract weight loss; indeed, it was correlated with further weight loss at month 3. Activation in a 30 network of prefrontal regions associated with self-control could contribute to individual differences 31 in weight loss and maintenance, whereas we failed to find that the hormonal adaptations play a 32 major role. (which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.
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