FA=high-fat, ab libitum (eat-at-will) diet, FT=high-fat, time-restricted diet, NA=normal ab libitum (eat-at-will) diet, NT=normal diet, time-restricted
Diets tell you what you eat, but a new study suggests when you eat matters too. Of two groups of mice who were fed the same high-fat diet, the mice who could eat around the clock were much heavier than those who had food restricted to eight hours per day, in a new study published in Cell Metabolism.
Researchers in the study gave the mice a special high-fat chow, 61% of whose calories come from fat (compared to just 13% in normal feed). The mice who chowed down all day and night became, unsurprisingly, obese, but the ones who ate the same amount of hi-fat food in only eight hours per day did not. Their body weight was comparable to mice fed an equivalent amount of calories on normal feed.
This being a study in Cell Metabolism, the researchers didn’t stop with just weighing the mice; they did a lot of molecular experiments to work out the link between timing and weight gain. Mice on high-fat, eat-whenever diets had the insulin problems associated with obesity-induced diabetes and lower expression of genes linked to breaking down fats in the liver, leading to fat accumulating in the liver. The high-fat, time-restricted diets did not have those problems.
This might make sense in light of our circadian rhythms, which are the approximately 24-hour cycles that govern sleep as well as metabolic functions such when the liver secretes bile and the pancreas insulin. Previous research has found that sleep-deprived and jetlagged people, whose circadian rhythms are out of whack, are at risk for weight gain. The current study adds to the link between circadian rhythms and weight, suggesting that eating fat at odd hours disrupts daily metabolic cycles.
Image courtesy of M. Hatori et al / Cell Metabolism