Eating a late dinner caused a 10 percent reduction in fat burning compared to an early dinner.
The amount of time that you’re awake after the meal may also play a part.
Are you the type of person who eats dinner early in the evening, or do you eat late and then immediately go to bed? These habits may have more to do with how your body metabolizes your food than you may think.
A recent study published in the Journal of Clinical Endocrinology & Metabolism found that if you’re trying to lose weight, when you eat dinner compared to when you go to bed might play a key role.
The study, which was conducted in a small 20-person sample (10 male and 10 female participants), found that eating a later dinner lowered the body’s fat oxidation—the breaking down of fatty acids in a person’s body.
Before coming in for observation, people wore trackers to monitor their activity and sleep habits. The participants were then randomly sorted into two different observation groups—one group of 10 ate an “early” dinner at 6 p.m. and the other half ate a “late” dinner at 10 p.m. On the second observation, the groups switched their mealtimes. For both observations, all participants went to bed at 11 p.m.
Researchers found that eating a late dinner caused a 10 percent reduction in fat burning overnight compared to eating an early dinner, study author Jonathan Jun, M.D., associate professor of medicine at the Johns Hopkins University School of Medicine in Baltimore told Bicycling.
And while researchers didn’t see weight gain in the participants—the observation period wasn’t long enough to see weight change that quickly—it is likely that this behavior over time may lead to weight gain.
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Why might a late dinner cause weight gain? When you fall asleep, your metabolic rate drops; you’re not moving around, exercising, or doing other things that require a lot of energy. If you eat and are then immediately inactive, that could lead to burning less fat, Jun explained.
Another possibility is related to your body’s circadian rhythm. As the day transitions to night, your body’s digestive system and energy expending system change as well, which may decrease your body’s ability to deal with the fat you eat at that point.
Something the researchers plan to study further—how your sleep timing affects weight gain. For example, while most people were awake for hours after eating dinner at 6 p.m., giving the body time to digest before sleep, they were not awake as long after eating dinner at 10 p.m., which led to the digestive period after eating to overlap with people being asleep, which likely affected how the body was able to metabolize the meal, Jun said. “Early birds” (those who typically wake early and go to sleep early) were more affected by the late-night meal than “night owls” (those who typically wake later and go to sleep later).
So what does this mean for cyclists? “For people that are interested in weight loss, our study would suggest that front-loading calories in day, such as having a big breakfast, and eating smaller meals in the evening might help you lose weight if you adopt that pattern,” Jun said.
So, if you like to recover postride with a big meal and are trying to lose weight, it may be more beneficial to exercise in the morning and fuel with a larger breakfast (previous research has found that a larger breakfast may help boost your metabolism) and lunch, but a smaller, earlier dinner. However, if you’re working toward a different goal, this eating pattern might not work for you.
Overall, it’s not just the timing of your meal that matters, Jun said. It also depends on your sleep habits and circadian rhythm. So, if you eat dinner late but also stay up late, your meal may not have as much effect on weight loss as if you eat later and go to bed early.
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