Snacking may cut your lifespan, study finds: Mice who spaced out their meals lived longer and healthier than others - regardless of what they ate

• e-mail

Eating little and often may be damaging to your overall health and lifespan, scientists led by the National Institute on Aging claim.

Studying mice, researchers showed those who left more time between eating lived longer and were generally healthier than their snack-prone peers.

Mice who 'fasted' between meals had later onset of age-related diseases and healthier glucose levels - regardless of what food or drink the mice consumed. 

Controversially, they found that mice lived the longest if they only ate once a day. 

The findings, published today in the journal Cell Metabolism, call into question the popular dieting approach of eating snacks and small meals every couple of hours.

The study, published today in the journal Cell Metabolism, found mice who 'fasted' between meals had later onset of age-related diseases and healthier glucose levels

The 'little and often' approach is often touted as a way to 'keep metabolism going'.

However, the team of researchers from three institutions showed that fasting is the pivotal factor that affects metabolic health.

'This study showed that mice who ate one meal per day, and thus had the longest fasting period, seemed to have a longer lifespan and better outcomes for common age-related liver disease and metabolic disorders,' said Richard J. Hodes, MD, director of the National Institute on Aging (NIA).

'These intriguing results in an animal model show that the interplay of total caloric intake and the length of feeding and fasting periods deserves a closer look.' 

For the study, 292 male mice were divided into two groups.  

One was fed a 'healthy' diet: few purified sugars and fat, plenty of protein and plenty of fiber. The other had the opposite: fatty, sweet and carby. 

Within each group, there were three subgroups (so, six groups in total).  

The first subgroup could eat whenever they wanted. The second were given 30 percent fewer calories a day. The third group had the same amount of calories as the first group, but all consumed in one meal.

They were then monitored over time, with scientists looking for signs of poor or improved metabolic health, and changes in lifespan. Each mouse was analyzed post-mortem.    

The second and third groups (in both the healthy half and the unhealthy half) adopted similar approaches to eating: because they couldn't eat whenever they wanted, they would gobble up their food when it arrived, leaving longer spaces between meals. Meanwhile, the first group would leisurely take their time, and snack around the clock. 

To the researchers' surprise, there was another correlation between the second and third groups: regardless of what they were eating, they lived longer and were generally healthier than the first groups.  

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

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

This study is one of the first to scrutinize fasting times (i.e. the space of time between meals), explains the study's lead author, Rafael de Cabo, PhD, chief of the Translational Gerontology Branch of the NIA Intramural Research Program.

Calorie restriction has been a popular subject in labs since the early 1900s. But looking at when we eat, rather than simply what we eat, is a relatively new concept.  

'Increasing daily fasting times, without a reduction of calories and regardless of the type of diet consumed, resulted in overall improvements in health and survival in male mice,' said de Cabo. 

'Perhaps this extended daily fasting period enables repair and maintenance mechanisms that would be absent in a continuous exposure to food.'

The study is limited by the fact that it only involved male mice. 

Next, Dr de Cabo hopes to look at both genders and other animal species to get closer to understanding just how much of these findings would translate to humans.