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The Science Behind Late-Night Eating and Weight Gain

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Maintaining a healthy weight is an essential part of overall well-being. While we often think about what we eat to keep our weight in check, recent research has shown that the time of day we eat is also a significant factor. In a small randomized controlled trial, researchers at Harvard University examined the effects of late-night eating on weight gain and found some surprising results.

The study, which was published on Oct. 4, 2022, in Cell Metabolism, asked 16 overweight or obese participants to test two different meal schedules with identical diets. In the first schedule, participants ate breakfast, lunch, and dinner, but finished their last meal six-and-a-half hours before bedtime. In the second schedule, the same meals were bumped four hours later in the day, ending two-and-a-half hours before bedtime. Over the course of six days, scientists measured the participants’ appetite-regulating hormones, body temperatures, calorie expenditure, and fat cells.

The findings were clear: eating later in the day increased participants' hunger, decreased the number of calories they burned, and promoted fat storage. This could potentially lead to weight gain over time. The study suggests that while it's okay to have the occasional late supper, making it a habit is not recommended.

One possible explanation for this effect is that our bodies naturally burn fewer calories at night, when we're typically less active. The metabolism slows down during sleep, and eating late at night can interfere with this process. When we eat close to bedtime, the body is more likely to store those calories as fat, rather than burning them for energy.

Additionally, eating late at night can disrupt our sleep patterns, leading to less restful sleep. Poor sleep quality has been linked to weight gain, as it can affect our hormone levels and appetite regulation. This can create a vicious cycle, as poor sleep can lead to overeating, which in turn can interfere with sleep.

So what can we do to avoid late-night snacking and maintain a healthy weight? One strategy is to establish a regular meal schedule and stick to it as closely as possible. This can help regulate our hunger and prevent overeating. It's also helpful to plan ahead and have healthy snacks available for times when we do feel hungry outside of our regular meal times.

Finally, it's important to be mindful of our eating habits and avoid mindless snacking. Eating in front of the TV or while working can lead to overeating and poor food choices. Instead, try to eat at a table and savor your food, paying attention to the flavors and textures.

In conclusion, this study by Harvard researchers highlights the importance of meal scheduling in maintaining a healthy weight. Eating later in the day can lead to increased hunger, decreased calorie expenditure, and fat storage. By establishing a regular meal schedule, being mindful of our eating habits, and avoiding late-night snacking, we can maintain a healthy weight and improve our overall health and well-being.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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