Published by the Students of Johns Hopkins since 1896
October 16, 2021

Eating at night does not cause weight gain

By SABRINA CHEN | February 9, 2017

Anyone who has dieted has heard the myth: To lose weight, “Eat breakfast like a king, lunch like a prince and dinner like a pauper.”

Many nutritionists argue that our body’s metabolism slows at night, especially when we sleep. Therefore the calories we consume at night could count more than the calories we eat throughout the day, when we are active.

In 2008 the journal Obesity published an article that stated even when the total calories consumed were the same, eating at night could cause twice as much weight gain. The study had been carried out at Northwestern University using mice as models.

However Obesity recently published a new finding in their current edition of the journal. Scientists have used the rhesus monkey model to tackle the myth of weight gain from late night eating. The study was done at the Oregon National Primate Research Center at the Oregon Health and Science University (OHSU).

“We’ve all been told at one point in our lives that we should avoid eating meals late at night since it will lead to weight gain. However, our research in rhesus monkeys, which are considered an excellent model for studying primate (man and monkey) obesity issues, showed that eating at night is no more likely to promote weight gain than eating during the day,” Judy Cameron, a senior scientist in the Divisions of Reproductive Sciences and Neuroscience at the OHSU Oregon National Primate Research Center, said in a press release. “Of course this research does not suggest that snacking at night after eating your normal daily ration of calories is a good idea.”

To conduct the study researchers placed 16 female monkeys on a high-fat diet similar to that of humans in the United States and other western countries. The researchers studied the monkeys for a year and observed that monkeys ate between six percent and 64 percent of their total calories at night.

This was an interesting parallel to humans who eat approximately 24 percent to 65 percent of their total calories at night.

“It was really interesting to see that the monkeys who ate most of their food at night were no more likely to gain weight than monkeys who rarely ate at night,” Elinor Sullivan, an OHSU graduate student conducting research along with Cameron at the Oregon National Primate Research Center, said in a press release. “This suggests that calories cause weight gain no matter when you eat them.”

Furthermore during the study, the monkeys had their ovaries removed to simulate a menopause-like state in the monkeys compared to human female menopause. The scientists did this because they wanted to study how the contribution of menopause could add to weight gain in middle-aged women.

The study showed that monkeys gained about five percent more weight after their ovaries were removed. This could show that the ovarian hormones can contribute to weight gain in humans as well.

However there are still many good reasons to be cautious about eating at night. One reason is that many people use late night snacking to cope with boredom or stress. Thus these snacking portions are less likely to be controlled and more likely to consist of high calorie foods such as chips, soda, cookies or candy.

Furthermore because many of these snacks are usually consumed in front of a television or computer or while studying, people don’t realize that they are eating far more than they planned to, because they are not paying attention to their food while eating. In addition eating at night can also cause indigestion and sleeping problems.

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