We’ve all heard it before- avoid midnight snacking! Those late night runs to the fridge (or pantry) have been vilified for packing on the pounds from time immemorial. A recent study conducted by the Salk Institute shows that this is more than an old wives tale- eating at all hours may indeed contribute to obesity. The good news? Eating within a 9-12 hour window can not only prevent obesity, but has also been shown to reverse it.

Here’s the experiment breakdown: Over 38 weeks, scientists fed four groups of mice four different diets- high fat, high fructose, high fat and high sucrose, and plain mouse kibble. The total calories consumed by each group were the same. Within each group, some mice were kept to “Time Restricted Feeding (TRF)” windows of 9, 12 or 15 hours, while others ate whenever they wanted. Additionally, some of the mice on TRF were allowed to “cheat” on weekends and eat whenever they liked, while some of the eat-anytime mice were switched over to TRF part way through the experiment.

The results? The mice in the 9 and 12 hour groups remained fit regardless of their diets, while the eat-anytime mice grew obese. The mice allowed to cheat on weekends also remained fit and healthy. Excitingly, the obese eat-anytime mice that were switched over to TRF lost some of the weight they had gained. The study demonstrates that TRF is effective against high-fat, high-fructose, and high-sucrose diets without restricting calories, even when weekends are eat-anytime cheat periods. (Click here for the study and a great illustration of the test) While the study has thus far only been tested on mice, the scientists are optimistic about human implications.

So what does this mean for us humans? Restricting your eating hours to a 9-12 hour window during the day, starting from whenever you first eat in the morning (coffee counts!), may help prevent weight gain, and switching to a 9-12 hour window may help shed pounds as well as prevent against metabolic diseases.