The idea that eating after a certain hour causes weight gain is one of the most repeated pieces of nutrition advice out there. Cut off at 7 p.m., stop eating after 8, nothing past 9. The specific number varies depending on who you ask, but the underlying belief is the same: calories consumed at night are more likely to end up stored as fat. It’s a compelling rule, but also not quite right.

Your body doesn’t actually have a metabolic cutoff time. Calories don’t behave differently at 9 p.m. than they do at noon. Weight gain or loss over time is driven by total caloric intake relative to total caloric expenditure, and the clock on the wall is not a variable in that equation. Multiple controlled studies comparing groups eating the same number of calories at different times of day have found no significant difference in body composition outcomes based on meal timing alone.

Where late-night eating does cause problems is behavioral, not biological. People who eat late at night tend to do so in addition to their regular daily intake. Evening eating is often mindless, driven by boredom, stress, or habit rather than hunger. The foods chosen tend to be calorie-dense and easy to overeat. A bowl of cereal, a handful of chips, leftover takeout. None of these are inherently worse at 10 p.m., but the context in which they get eaten often leads to a consistent caloric surplus over time, producing measurable weight gain.

There’s also a circadian effect worth noting. Some research suggests that eating close to bedtime can affect sleep quality for certain people, and poor sleep is independently linked to increased appetite and cravings the following day. So the downstream effects of late eating on your overall diet pattern can be real, even if the direct metabolic impact is not.

If you happen to be hungry at night, eating something is not going to derail your progress on its own. What matters is whether that late meal is pushing your total daily intake beyond what your body needs, and whether it’s becoming a nightly habit built around something other than actual hunger.

The time on the clock is not the problem. The pattern around it usually is.