Confining meals to a 12-hour window and fasting for the remainder of the day makes a significant difference to whether fat is stored or burned up by the body, according to a study.

Researchers at The Salk Institute in the US have found that people who don’t have access to healthy diets can practice time-restricted feeding to shed pounds and fight high cholesterol, diabetes and obesity.

A study was conducted with 400 mice, ranging from normal to obese, putting the rodents on various types of diets and time restrictions.

The results, published in the journal Cell Metabolism, showed mice that were fed a high fat diet – but allowed access to food for only 12 hours per day – were healthier and slimmer than mice given access to the same food for the whole day – even though the two groups consumed the same number of calories.

There was no change in the data for mice on diets that featured high levels of fat, sugar, or fruit sugars.

Time-restricted mice that were allowed an occasional late-night feeding splurge did not demonstrate any significant changes to their body mass, which the study’s author – postdoctoral researcher Amandine Chaix – said meant that an occasional late night takeaway was unlikely to harm the body’s metabolism. Regularly eating late at night, however, would have a serious impact.

“The fact that it worked no matter what the diet and the fact that it worked over the weekend and weekdays was a very nice surprise,” said Chaix.

The changes in the body composition of the mice involved in the survey were significant. Mice that had become obese by eating whenever they liked during the day lost five per cent of their bodyweight when the time restricted feeding was implemented. At the end of the 38-week study, they were 25 per cent lighter than the group who had continued to eat freely.

Mice on a healthy diet did not lose more weight but they gained muscle mass.

“They changed their body composition,” said associate professor Satchidananda Panda. “That brings up the question – what happens? Are these mice maintaining their muscle mass, which might have been lost with free feeding, or are they gaining muscle mass?”