Dieting wisdom tells us that we should be eating little and often, but scientists led by the National Institute on Aging claim that it may actually be damaging to your health and could shorten your lifespan.

Rodent studies showed researcher that those mice who left more time between eating lived longer and were generally healthier than their snack-eating companions. Mice who ‘fasted’ between meals tended to have later onset of age-related diseases and also healthier glucose levels. This was interestingly regardless of what food or drink the mice consumed.

The researchers found that mice lived longest when they only ate once a day.

The findings were published in the journal Cell Metabolism, and it puts a question mark over the popular dieting approach of eating small meals and snacks every couple of hours. The ‘grazing’ approach is often said to be a way to keep the metabolism running properly, but the team of researchers showed that fasting is actually the main factor in metabolic health.

The study divided 292 male mice into two groups:

Once group was fed a healthy diet of very few purified sugars and fats, lots of protein and plenty of fiber. The other group had the opposite type of diet – fatty, carby and sweet.

In each group there were three subgroups, so there were six groups in total. The first subgroup could eat when they wanted, the second group were given 30 percent fewer calories per day, and the third group had the same amount of calories as the first group, but all eaten in one meal.

The mice were all monitored over time, with the researchers looking for signs or bad or improved metabolic health, and any changes in lifespan. The mice were analysed post-mortem.

The second and third subgroups in both of the two main groups took similar approaches to their food. They would eat it quickly as soon as it arrived, because they couldn’t eat whenever they wanted. This meant they left long spaces between meals. The first group would take their time eating and snack when they felt like it.


The researchers were surprised to discover that the second and third groups in both main groups lived longer and were healthier than the first groups – regardless of what they were eating.

Meal-fed and calorie-restricted mice both showed delays in age-related damage to the liver and other organs, and they showed extended longevity.

The calorie restricted mice also showed significant improvement in fasting glucose and insulin levels compared to the other groups.

Calorie restriction has been popular in studies since the early 1900’s, but investigating when we eat rather than just what we eat is a fairly new idea.

The author of the study, Rafael de Cabo, PhD, suggests that perhaps increasing daily fasting times without changing the amount or type of food consumed results in health improvements and survival in male mice.

More research needs to be done to see how this will affect larger animals and humans, but it’s an encouraging start.