March 28, 2023: Weight is a subject that occupies the minds of almost half the world’s population or more. Dieting with caloric restrictions is the most common and popular method of losing weight. But the moment this regime is stopped, people tend to regain the lost weight. It is a known fact that dieters and exercise regime followers regain half of their lost pounds within two years and around 80% after five.
According to the World Health Organization, obesity or overweight is currently growing at epidemic proportions, with over 4 million deaths annually. The global weight management market size was $224.27 billion in 2021 and is expected to surpass USD 405.4 billion by 2030. Weight gain or loss is more a hormonal and biological matter of the body and less about following a certain diet and exercise regime.
Inhibiting neural pathways
A new study from the Max Planck Institute for Metabolism Research (MPIMR) and Harvard Medical School have some positive news for those struggling to keep the weight regain off. The researchers say that significant changes occur in the neural pathways when dieting and that mediate feelings of hunger. Inhibiting these signals may help scientists develop treatments that better assist people in maintaining their weight.
“People have looked mainly at the short-term effects after dieting,” said Henning Fenselau, a researcher at MPIMR, who led the study. “We wanted to see what changes in the brain in the long term.”
In an experiment with mice, they monitored the brain circuitry of mice put on a diet, focusing on the Agouti-Related Peptide (AgRP) neurons in the hypothalamus. Hypothalamic circuits that control hunger drive determine body weight. They found that the neuronal pathways to the AgRP neurons changed and became overactive when the animals were on a diet and continued to be high, resulting in extreme hunger signals that led to greater food intake and quicker weight gain.
“This work increases understanding of how neural wiring diagrams control hunger,” said co-author Bradford Lowell from Harvard Medical School. “We had previously uncovered a key set of upstream neurons that physically synapse onto and excite AgRP hunger neurons. In our present study, we find that the physical neurotransmitter connection between these two neurons, in a process called synaptic plasticity, greatly increases with dieting and weight loss, and this leads to long-lasting excessive hunger.”
When the researchers inhibited the connection between those neurons, AgRP activity decreased and the animals’ response to food was more regulated leading to lesser weight gain.
Fenselau said that the goal was to find therapies for humans that could help maintain body weight loss after dieting. This means more research into the mechanisms of neural pathways.