You may not realize it, but that is a loaded question.
For years, the standard nutrition response has been “no” — it’s the overall balance between calorie intake and energy outgo that matters, not what time of day you eat.
And that’s still the take of the Academy of Nutrition and Dietetics (formerly the American Dietetic Association). If you go to its website,http://www.eatright.org, and search for “night snack,” you’ll find lots of great guidance, including the notion that eating “late-evening calories are no more likely to promote weight gain than calories eaten at other times of the day.”
But recent studies are beginning to prompt some researchers to reconsider.
Most recently, in a study published in June in the journal Cell, researchers reported findings about two groups of mice fed a high-fat diet. The mice that were fed frequently throughout the day, disrupting their normal nighttime feeding cycle, were more likely to become obese and suffer from related conditions even though their calorie intake was the same as mice fed during normal feeding times. The mice given food only at the “right” feeding time (for mice, it’s natural to eat at night) had better usage of nutrients and expenditure of energy.
A study in the journal Obesity in late 2009 had similar findings: In that study, mice fed only during their natural feeding time weighed significantly less than mice fed at the wrong times. The mice fed at the wrong times also tended to be less active and to eat slightly more than the other group — a bad combination.
The researchers involved in these studies suggest that our eating patterns should adjust to circadian rhythms — that is, you should eat during the day and avoid snacks at night, especially if you want to maintain or lose weight.
Whether or not you accept the researchers’ conclusions, you still might want to consider whether nighttime snacks are the best choice for you. The Academy of Nutrition and Dietetics itself recommends pausing to think if you’re tempted to eat a nighttime snack: Are you eating because you’re hungry, or because you’re bored or anxious, or have just gotten into the habit of having that snack?
Besides, if you’re trying to lose weight, giving yourself a time-related cutoff for eating could help you trim the number of overall calories you consume on a day-to-day basis. It could be a good place to start.