Q. Does eating late really make you gain weight?
A. The conventional wisdom that eating late leads to weight gain has some recent evidence to back it up. Kelly Glazer Baron, a circadian rhythm and sleep researcher at Northwestern University’s Feinberg School of Medicine, says that one factor is sleep deprivation: People who stay up late are more likely to be sleep-deprived, and lack of sleep could affect the metabolism. Studies also show that people who sleep less and are up late tend to consume more calories.
What’s not yet clear is whether our internal clocks affect how we metabolize food. Groups like the American Dietetic Association say that it’s the amount of calories you eat and not the timing that matters. But some researchers, including Baron, disagree. “There are multiple studies showing that there is a higher weight with eating late, even with the same calories,” she says. A recent study of dieters in Spain found that those who ate their main meal before 3 p.m. lost more weight than those who ate their main meal later in the afternoon.
“I really hesitate to say eating late is bad for you,” Baron says, but she believes the timing of eating could potentially help people manage their weight, if researchers can learn more about its effects on the body. For now, she says that late-night eaters should pay attention to the quality of food they eat at night, and keeping their activity level and calorie intake in balance.