Health
Scientists have identified a brain pathway in mice that may explain why people tend to regain lost weight. The mechanism involves cells located in the hypothalamus called AgRP neurons, which are activated when the body is low on fuel and can cause intense hunger.
Researchers used optogenetics to measure activity in the post-mortem brains of nine mice, five of whom had fasted for 16 hours. The mice that had fasted showed more activity in a part of the hypothalamus called the paraventricular hypothalamic nucleus (PVH). To further test the connection between PVH neurons and AgRP neurons, researchers silenced the PVH neurons in a group of mice and tracked the amount of food the mice ate over 24 hours. On average, the mice ate about 33% less food than the control group and regained less weight over the course of seven days.
The results suggest that weight regain is driven by an increase in signalling from PVH neurons to AgRP neurons. This finding is an important step towards understanding hunger, and future therapies that dampen the signalling from PVH neurons could help people maintain weight loss. However, more research is needed to understand the function of PVH neurons and the consequences of silencing them.