The pleasure we derive from food is nature’s way of ensuring that we don’t let ourselves starve, explains Dr Giles Yeo of the University of Cambridge’s Metabolic Research Laboratories. And our penchant for second helpings was bred into us throughout millennia of unpredictable food supply, allowing us to squirrel away a few extra calories for a rainy day.
Our survival as a species probably owes a lot to these mechanisms. But for 21st Century Man, who is more likely to hunt and gather in a supermarket than across the windy plains, they can easily translate into a spreading waistline. According to the World Health Organization, overweight and obesity are the fifth leading risk of death globally.
Go with your gut
In fact, says Dr Yeo, the body knows if it has received enough calories of the right kind. There are two types of signal it sends to the brain, he adds.
“Some come from fat – these basically indicate how long you can survive without food. The other key information your brain needs is how much you ate at your last meal,” he says. “The best part of your body for determining this is your gastrointestinal tract. This information is conveyed to the brain via a release of hormones.”
Dr Yeo is the coordinator of the EU-funded project EurOCHIP, which studied this communication between the gastrointestinal tract and the brain.
“It’s amazing how little is known about the pathways,” he says. “We know the key hormones, we know certain things that happen, but we still don’t know exactly how the body releases those hormones with respect to different types of meal and to different types of food, and how this influences the way the brain responds.”
Thanks to EurOCHIP, the fog is clearing. The project approached the question from several angles to improve the prevention and treatment of obesity. It has generated new knowledge about the hormones, genes and brain responses that shape our appetite and possible ways of keeping it in check.
EurOCHIP’s comprehensive approach reflects the complexity of the issue. Many factors combine in our decision to eat or not to eat, and several parts of the brain are involved. While the information from the gut is processed in the hypothalamus, the pleasure we may get from a meal is associated with other parts of the brain.
The fact that we are more likely to get carried away when there is chocolate involved than when we are offered leftover Brussels sprouts is linked to these so-called ‘reward centres’, which can overrule our better instincts.
One of EurOCHIP’s main outcomes is the development of a blend of gut hormones that mimics the effects of a gastric bypass, convincing the brain to reduce food intake. Gastric bypass surgery, currently the most effective way of helping particularly heavy people to lose weight, reduces the size of the stomach or the length of the intestine. The rationale, originally, was that it would decrease the number of calories that the body could absorb.
Not so, says Dr Yeo. In fact, the bypass means that initial steps in the body’s processing of food are skipped, and that the intestine receives content in a form for which it has not evolved. As a result, he explains, the gut releases a different combination of hormones.
“It is this different mix, which is sensed by the brain, that actually makes you eat less,” he says.
EurOCHIP, which benefited from nearly EUR 3 million of funding from the EU’s Seventh Framework Programme, has developed and refined a combination of two gut hormones to trigger the same effect pharmacologically. This promising mixture is currently being trialled.