A study conducted by Liane Schmidt (INSERM) and Hilke Plassmann (INSEAD’s Octapharma Chaired Professor of Decision Neuroscience) both researchers at the Paris Brain Institute establishes for the first time a link between weight loss, the connectivity of the brain’s system at rest and hormonal regulation of satiety. The results are published in Brain Communication.
Obesity is a multifactorial condition, integrating environmental, hormonal, psychological and physiological dimensions. One dimension remains little explored, that of the neurobiological bases and to what extent these can predict weight variations.
Previous studies have identified that increased activity of reward and motivation systems in the brain in response to seeing foods in participants with obesity, but had not taken into account that the global changes associated with obesity, particularly metabolic changes, could have an impact on the functioning of these brain systems.
To obtain a more integrated view of the issue, Liane Schmidt, HIlke Plassman and their collaborators some at the Nutrition Department of the Pitié-Salpêtrière Hospital at Sorbonne University conducted a study involving 44 participants, 14 patients with obesity before and after they had undergone bariatric surgery, and 30 age-matched controls also examined twice over the same time span. In a first step, the team compared the connectivity of brain regions involved in reward at rest. They then used these results to assess whether connectivity could predict weight loss or weight gain over a period of 8 months.
Two connectivity networks in the reward system varied between obese and non-obese subjects: that between the ventromedial prefrontal cortex and the ventral striatum and that between the ventromedial and dorsolateral prefrontal cortex. On the other hand, only the connectivity of the former was able to predict weight changes in obese participants over time and after bariatric surgery.
“We show that before surgery, participants with obesity had decreased activity in the brain’s reward system compared to lean participants, and that this activity returns to a more stable state after surgery and weight loss. In addition, this reward system activity was a good predictor of the ability to lose weight. Thus, the more the resting state activity in the reward system changed over time, the greater the weight loss over time.”
explains Liane Schmidt, co-team leader of the Control Interoception and Attention Team at the Paris Brain Institute.
In the last part of the study, the team linked the change in brain connectivity to a third variable: the satiety hormone leptin. In participants with obesity, leptin levels are very high but leptin does not function properly. After surgery leptin levels decrease and can better signal satiety again. The Paris Brain Institute team showed that change of the brain’s reward system activity at rest is correlated with a decrease in leptin resistance after bariatric surgery.
Schmidt L, Medawar E, Aron-Wisnewsky J, Genser L, Poitou C, Clément K, Plassmann H. Brain Commun. 2021 Feb