Does eating at night make you gain weight?

If you have asked this question, you are not alone. 

I’ve heard this claim thrown around so I decided to delve into the research. 

In this article, we go explore the common perception that eating at night leads to weight gain and if it has any merit. 

So let’s dive in. 

What does the research say about weight gain and eating at night? 

Study 1

In a study conducted in 2009 on 2 groups of mice, the timing of their feedings showed differences in weight gain. The two groups were given identical diets of 60% fat.

One group of mice was fed during daylight hours and the other group was fed during hours of no light. Since mice are nocturnal, when the mice eat during the day, it simulates humans eating at night, and when the mice eat at night, it simulates humans eating during the day.

At the end of the 6-week study, the mice had consumed approximately the same amount of calories and performed the same amount of exercise. However, the mice who ate at night (when they normally would eat) had a 20% increase in weight gain while the mice who ate during the day (when they would normally be sleeping) posted an average of 48% percent increase in body weight.

This study shows a possible correlation between the timing of food consumption in relation to an organism’s natural circadian rhythm.

Our circadian clock governs our daily cycles of feeding, activity, and sleep, with respect to external light and dark cycles. Recent studies have found that the timing of meals may matter in the balance of caloric intake and expenditure, as the body’s internal clock also regulates energy use.

Study 2

In another study conducted at the Oregon National Primate Research Center consisted of 16 female rhesus monkeys. Monkeys, being primates, are considered a great model for studying human obesity.

In the study, the monkeys were fed high-fat diets similar to humans and the monkeys who ate most of their food at night were no more likely to gain weight than the monkeys who rarely ate at night.

Study 3

In a study conducted by Northwestern University’s Feinberg School of Medicine, 23 “late” sleepers were compared with 28 “normal” sleepers. “Late” sleepers constituted those that went to bed at around 3:45 am and woke up by 10:45 am while “normal” sleepers included those that went to sleep by 12:30 am and up by 8 am. The study showed that the “late” sleepers consumed an average of 248 extra calories per day, which occurred mainly at dinner and later at night. They ate half the fruits and vegetables as their “normal” sleeper counterparts, twice the fast food, and more full calorie sodas.  A possible reason for this finding is that there are not as many healthy food options late at night, and thus, people will eat whatever they can get their hands on to support their late night craving.

Study 4

In another study conducted on mice by researchers at the University of Haifa in Israel and Ohio State University suggested that there may be more to weight gain than simple calorie intake and expenditure.  The study showed that dim and bright light exposure to mice at night significantly increased the BMI and glucose tolerance level of the mice in comparison to the group of mice that lived in the normal dark/light cycle.

The reason as to why this occurred is not quite clear yet, but researchers believe that low levels of light are affecting the metabolic signals during night time when these mice eat and maybe causing a correlation of eating at night and weight gain.

Study 5

In another study which involved 2 different meal patterns, one group consumed more calories earlier in the day and the other group consumed more calories later in the day. Those who ate larger meals later in the day actually had more favorable results. Although those that had their meals earlier in the day had a slightly greater weight loss, much of it was muscle mass. Those who had their meals later in the day, however, had a better maintenance of a fat-free mass.

Study 6

In another study on the nutrient intake and caloric expenditure on 57 young women during Ramadan fasting resulted in a significant reduction in body weight and BMI.

During Ramadan, Muslims abstain from the consumption of food and fluids from sunrise to sunset. Therefore, the only intake of food and water is during nighttime. 

During the study, the mean energy intake and physical activity level was not significantly different before Ramadan versus during Ramadan. The number of meals decreased during Ramadan as opposed to before the holiday.

The study revealed that there was a significant weight loss during Ramadan, however, and that there may be a correlation between eating at night and weight gain.

The Verdict: Does eating at night make you gain weight?

In summary, there is very little research showing that humans consuming meals late at night is linked to greater weight gain.

However, minimizing food intake at night might be a good option to minimize caloric intake. For the most part, and I say “most part” because very few things in nutrition are absolute, a calorie is a calorie is a calorie.

Whether consuming that calorie in the morning, the afternoon, or at night, it is most likely all the same. I say most likely because of the many rodent studies. These studies have brought up new information that is not completely understood.

These studies have shown a possible correlation between weight gain and eating at “wrong” times. These studies show that there may be more to weight gain than simply calories and that the body’s circadian rhythms and internal processes may be more complex than we are aware of in terms of weight gain.

If you have any questions regarding the question of “does eating at night make you gain weight?” or simply the topic of eating at night and weight gain, don’t hesitate to ask.


Daniel Maman

Daniel Maman's two biggest passions in life are health and fitness. He is a certified personal trainer, has a degree in exercise science, and spends his free time keeping up to date with the latest research. In his free time, you can find him playing basketball, bouldering, and spoiling his dog, Luna.

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