High-fat diet 'stops brain from signalling when you are full'
By Nina Massey
Listening to your head is not always the answer when it comes to deciding whether or not to go back for second helpings.
A high-fat diet has been linked with turning off the signal in the brain that indicates when you are full.
The study published in the Journal of Clinical Investigation suggests a previously unknown gut-brain connection that helps explain how extra servings lead to weight gain.
Corresponding author Dr Makoto Fukuda, assistant professor of paediatrics at Baylor College of Medicine, said: "We have uncovered a new piece of the complex puzzle of how the body manages energy balance and affects weight."
Researchers found that mice consuming a high-fat diet showed increased levels of gastric inhibitory polypeptide (GIP).
This hormone is produced in the gut and is involved in managing the body's energy balance.
In the study, scientists found that excess GIP travels through the blood to the brain, where it inhibits the action of leptin - the satiety hormone.
Consequently, the animals continued eating and gained weight.
Blocking the interaction of GIP with the brain restores leptin's ability to inhibit appetite and results in weight loss in mice.
Scientists know leptin, a hormone produced by fat cells, is important in the control of body weight both in humans and mice.
While it usually triggers the sensation of feeling full when people have eaten enough, in obesity resulting from a high-fat diet or overeating, the body stops responding to leptin signals - it does not feel full and eating continues, leading to weight gain.
Dr Fukuda added: "We didn't know how a high-fat diet or overeating leads to leptin resistance.
"My colleagues and I started looking for what causes leptin resistance in the brain when we eat fatty foods.
"Using cultured brain slices in petri dishes we screened blood circulating factors for their ability to stop leptin actions.
"After several years of efforts, we discovered a connection between the gut hormone GIP and leptin."
The scientists acknowledge that while more research is needed, they speculate that these findings might one day be translated into weight loss strategies that restore the brain's ability to respond to leptin by inhibiting the anti-leptin effect of GIP.