The researchers, led by Dr. Fred W. Turek at Northwestern University, found that mice who were fed during the day (the time they would normally sleep) gained twice as much weight than those fed the same diet at night.
The mice were permitted to eat as much as they wanted during their designated feeding time, but were not allowed to eat at any other point. The average starting weight for both groups of mice was around 22 grams.
After sticking to the new schedule for six weeks, the mice who ate during the day weighed approximately 32 grams, while the mice who ate at their normal hours weighed an average of 27 grams. The calorie intake between the two groups was almost equal.
What does this mean for humans? According to MedPage Today:
“How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out,” said study leader Fred Turek… “We think some factors are under circadian control. Better timing of meals, which would require a change in behavior, could be a critical element in slowing the ever-increasing incidence of obesity.”
The researchers clarify that several other factors could play a role, such as body temperature and resting energy expenditure. They also reference the findings of previous studies which have indicated that humans are at an increased risk for weight gain when their circadian and behavior cycles are askew.
The researchers conclude:
“These findings, taken together with the present results indicate that the synchrony between circadian and metabolic processes plays an important role in the regulation of energy balance and body weight control.”