Not eating after 7 p.m. in and of itself may not help you lose weight. But regular eating beyond the traditional dinner hour may mess with your circadian rhythms, which may affect your weight.
Eating earlier in the day may not make you thinner by itself, but it may help your body burn more energy earlier in the day when you're more active.
Not Eating After 7 P.M.
By not eating after 7 p.m., you may train your body to become more efficient at burning fat. According to researchers in a June 2017 study at the Perelman School of Medicine of the University of Pennsylvania, frequent eating late at night, which they defined as anytime between 7 and 11 p.m., can affect your body's metabolism of fat. You'll burn your fat more slowly.
If you're actively trying to lose weight, you may be better off eating on a regular daytime schedule, and you might try not eating after 7 p.m. In the Perelman study, those who ate later gained weight, compared with those who ate between 8 a.m. and 7 p.m. This happened despite the fact that the two groups ate the same amount of food.
A July 2017 study of mice by the University of Texas Southwestern Medical Center looked at what happened when a species is off its normal schedule. This study followed mice, which are nocturnal. The mice were left to their normal schedule but fed a reduced diet at night and lost weight. Mice fed the same reduced diet but during the day when they would normally be asleep, didn't lose weight.
Another study published in October 2013 in the International Journal of Obesity followed women who ate their main meal at lunch. Those who ate lunch the latest lost less weight and lost weight at a slower rate than those who ate earlier.
Fat and Energy
Eating something at night, after your normal dinner hour or extending late into the evening, can cause the body to store those calories as fat rather than burn it as energy, according to Kelly Allison of the University of Pennsylvania's Center for Weight and Eating Disorders.
This is because the hormone ghrelin, which stimulates appetite, peaks earlier in the day, while the hormone leptin, which keeps you satisfied, peaks later in the day. This indicates that eating early helps you stay satisfied longer, according to the Perelman study.
Read more: The Ultimate Guide to Fat Loss
Circadian Rhythms and Eating
Your circadian rhythm is basically your 24-hour internal clock. For most adults, there's a drop in energy from 2 a.m. to 4 a.,m. and again from 1 p.m. to 3 p.m., usually just after lunch. Known as your sleep-wake cycle, it's controlled by your pituitary gland, and it's what tells you you're sleepy.
If you get enough sleep and have regular sleep habits, you may not notice these dips in energy. But eating late can be an important factor in body composition, according to a study in the November 2017 issue of the American Journal of Clinical Nutrition. Basically, your body will hold on to more fat.
The study found that when participants ate a meal within four hours of bedtime, the food they ate gave off a lower energy response than in those who ate earlier. The study also found that when a late bedtime becomes the norm, because of work, going to college or other reason, more food tends to be eaten during the last meal of the day. That can lead your body to store more fat, and cause you to build up more fat reserves.
Eating a small snack before bedtime, however, may be less consequential. Researchers who conducted a study that was published in the journal Nutrients in April 2015 found that eating a snack before bedtime, totaling 150 calories or less, typically doesn't cause a problem. This is most notable for athletes who may get hungry more often or diabetics who need to control their sugar levels.
- Penn Medicine News: "Timing Meals Later at Night Can Cause Weight Gain and Impair Fat Metabolism"
- University of Texas Southwestern Medical Center: "Study: Eating at ‘Wrong Time’ Affects Body Weight, Circadian Rhythms"
- American Journal of Clinical Nutrition: "Later Circadian Timing of Food Intake Is Associated With Increased Body Fat"
- Nutrients: "The Health Impact of Nighttime Eating: Old and New Perspectives"
- National Sleep Foundation: "What Is Circadian Rhythm?"
- International Journal of Obesity: "Timing of Food Intake Predicts Weight Loss Effectiveness"