Diet culture spews a lot of confusing ideas about how to lose weight, and often they’re completely contradictory. Some say calories in, calories out is the only equation you need. Others say intermittent fasting is key, or lots of fruit and vegetables, or no carbs at all. Who can keep track?
But it turns out one old diet adage may actually have scientific merit: Don’t eat late at night.
In the past, researchers found evidence that delayed late eating is associated with an increased risk of obesity, but the mechanisms behind the phenomenon were murky. Now, a new study has pinpointed some of the biological reasons why late-night snacking can make you gain weight compared to eating the exact same things earlier in the day.
Determining Why Timing Matters
A study published in Cell Metabolism by researchers at Brigham and Women’s Hospital looked at 16 individuals with body mass indexes in the overweight or obese range. They received a three-meal daily diet over the course of two six-day stays in the lab.
During the first visit, the meals began in the morning. On the second visit, the exact same meals were shifted four hours ahead starting in the early afternoon.
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Participants were instructed to maintain a fixed sleep and wake schedule for two to three weeks before starting each in-laboratory stay. They also followed identical diets and meal schedules at home for the last three days before entering the laboratory.
The participants regularly documented their hunger and appetite. They provided small blood samples throughout the day, along with measurements of body temperature and energy expenditure. Researchers also took fat tissue biopsies.
They found that eating late significantly increased appetite during the day, decreased energy expenditure during the day, and caused the study subject’s bodies to more readily store fat. But why?
Three Culprits Come To Light
The researchers hypothesized that hormones, metabolism, and molecular changes might all converge to cause a correlation between late-night eating and increased risks of obesity. This is what they found:
- The appetite-regulating hormone leptin, which signals fullness, decreased during a 24-hour period during the late-eating stay compared to the early-eating stay.
- Late eating was associated with lower daytime metabolism.
- Late eating triggered a gene expression that causes increased fat storage.
Resetting Your Eating Schedule
If you are a serial late-night eater, it can be tough to break the cycle. Plus, between hectic work days, taking care of the family, and other life obligations, we all don’t get guaranteed meal breaks.
Similar to forming (or breaking) any habit, it takes time and dedication. If you usually skip breakfast, start with something small. If possible, try to eat meals at similar times of the day. Over time, your body should begin to adjust to your new eating schedule.
Meal prep can be a great option when trying to sticking to a new schedule, especially if you find yourself eating late dinners. Sometimes something as simple as prepping and chopping ingredients ahead of time can save valuable minutes when throwing a meal together at night.