Why do people over-eat? Study claims to have found the reason

New Delhi: Working odd hours or night shifts was found to disrupt signals liver sends to the brain telling it if eating is happening in sync with the body's clock, a result that researchers said could help treat the negative effects of eating at unusual times, such as overeating.

Eating at irregular times is said to be related to weight gain and diabetes, largely because it is not in sync with one's body clock, or circadian rhythm -- a 24-hour cycle of physical, mental, and behavioural changes, including sleeping and eating.

Researchers from the University of Pennsylvania, US, found that working unusual hours disturbs the liver's internal clock and its signals, because of which the brain overcompensates, thereby leading to overeating at the wrong times.

The results, published in the journal Science, suggested that targeting specific parts of the vagus nerve -- via which the liver communicates with the brain -- could help address overeating in people working night shifts or experiencing jet lag, the team said.

"Both mice and humans normally eat at times when they are awake and alert, and this circuit provides feedback from the liver to the central clock in the brain that keeps the system running smoothly," senior author Mitchell Lazar, a professor of diabetes and metabolic diseases, University of Pennsylvania, said.

"This feedback is through a nerve connection from the liver to the brain," Lazar said.

For the study, researchers looked at the REV-ERB genes in mice, which are known to have genetic material and biological processes similar to those in humans, and help them both control the body clock.

Turning off these genes made the mice's liver develop a faulty clock, because of which eating habits were found to change dramatically, with more food being consumed during less active hours, the team said.

However, the negative effects could be reversible, as cutting the nerve connection in obese mice was found to restore normal eating habits and reduce food intake.

"This suggests that targeting this liver-brain communication (route) could be a promising approach for weight management in individuals with disrupted circadian rhythms," author Lauren N Woodie, a post-doctoral researcher in Lazar's lab, said.

"Our findings reveal a homeostatic feedback signal that relies on communication between the liver and the brain to control circadian food intake patterns. This identifies the hepatic vagus nerve as a potential therapeutic target for obesity in the setting of chronodisruption," they wrote.