Does Eating At Night Cause Weight Gain?

We’ve probably all been told at one time or another that eating at night leads to weight gain.

But does it?

Not according to a study conducted at the Oregon Health and Science University’s National Primate Research Center.

In this study researchers placed 16 female rhesus monkeys on a high fat diet similar to that consumed in the US and other western countries. (Monkeys are considered a excellent model for studying human obesity issues.)

Over the course of one year, they recorded when the animals ate, how much they ate, and how much weight they gained.

The researchers found that the time at which the monkeys preferred to eat varied widely with some monkeys prefering to eat mostly during the day, and others preferring to do most of their eating at night. (Individual monkeys ate anywhere from a mere 6% to a whopping 64% of their total calories at night.)

But they also found that it made no difference when the animals ate most of their calories in terms of weight gain. In other words, monkeys who at primarily at night did NOT gain more weight than those who ate mostly during the day.

Interestingly, although all the animals did gain weight on the high fat diet they were fed, the researchers also found no clear correlation between total caloric intake and weight gain: the monkeys that ate more did NOT necessarily gain more weight.

This study once again demonstrates that caloric intake is NOT the sole determinant of weight gain. In fact, it might surprise you to learn that the whole idea of counting calories was “invented” in the early 1900s by an overweight Los Angeles physician.

For more on the history of calorie counting click here.