A stomach hormone that stimulates appetite seems to also promote the growth of new brain cells. This may explain why some people say that fasting makes them feel mentally sharper. The hormone is called ghrelin, and it is known as the ‘hunger hormone’ because whenever we go a few hours without food its levels rise in our blood to remind us to eat. But now there is strong evidence that ghrelin can also enhance your ability to think. 

Animals that have reduced-calorie diets have better mental abilities, and ghrelin might be part of the reason why. A higher level of ghrelin in mice improves their performance in learning and memory tests, and seems to boost the number of neuron connections in their brains. Jeffrey Davies at Swansea University, UK, and his team have found further evidence that ghrelin can stimulate brain cells to multiply (a process called neurogenesis), and this could be how ghrelin exerts its effects on memory. Neurogenesis creates ‘young’ brain cells which enhance the brain’s ability to form new memories. According to Davies: “These new neurons will fire more easily than old neurons, and this activates new memories.” 

The evidence is mounting that humans may also benefit from eating less to produce more ghrelin. Studies have shown that people on a diet of about 25% fewer calories than the daily recommended amount experience several health benefits. These include better control of blood sugar levels, which are related to brain functions. In an effort to harness some of the health benefits of a calorie-restricted diet, some people are turning to intermittent fasting. Going on a complete fast for days (or more) can be very difficult both physically and socially. A simpler way is to finish eating early in the day and then eat nothing until the following afternoon. If you have your last food at 18:00, and do not eat again until noon the next day, that gives you 18 hours of fasting with a minimum of disturbance to your life.