Check Your Clock Before You Take Your Next Bite.
Food is food, and calories are calories, right? Not so fast! A number of recent studies suggest that when you eat is as important as what you eat.
A 2012 study tested two groups of mice, both of which were given the same amount of high-fat, high-calorie food. One group could eat around the clock, while the other could only eat for 16 hours a day. Even though both groups consumed the exact same amount of the exact same foods, the group that fasted for eight hours were almost 40 percent leaner than the around-the-clock eaters.
The 24-hour eaters also developed high cholesterol and blood sugar, liver problems, and other metabolic diseases associated with obesity. A 2015 follow-up study showed that mice on an even longer time-restricted diet—being allowed to eat for only nine to twelve hours per day—had even better results.
Of course, what works for mice might not work for humans, so researchers have been performing studies to determine if these results can help people make healthier eating choices. Early signs look good not just for correlation, but for causation as well; specifically, human circadian rhythms have evolved to help us do a better job of processing calories and fat earlier in the day, rather than later.
A 2013 study in Spain found that people who ate a large lunch later in the day lost less weight and lost it more slowly than people who ate a large lunch earlier in the day. Other studies have tied nighttime fasting to improved glycemic regulation: that is, a person’s ability to regulate blood-sugar levels.
A 2015 study tied nightly fasting to a lower risk of breast cancer, and a 2016 study at Harvard Medical School found that shift workers who often have to invert their schedules and eat at night and fast during the day had a lowered glucose tolerance.
So what does this mean for you? To start, cut out the midnight snacks and late-night dinners. Whenever possible, eat your biggest meals before 3:00 pm and then begin to taper down. In order to lose significant weight, the calculus of “calories in” versus “calories out” still applies, but aligning your diet with your circadian rhythms will help you work with your body instead of against it.