You'd never eat two dinners at once, right? Except that maybe you (inadvertently) already do: Research shows that many women take in nearly half of their daily calories at or after dinner. What's more, one study found that a third of people downed 15 percent of their calories after 11 p.m.
In a way, evolution might be to blame: Humans were originally conditioned to chow down after sunset so they'd have the energy to get through the night. Some scientists believe that's why the body's hunger cycle still peaks at around 8 p.m. It's also why people might feel more cravings but less satisfaction when they eat in the evening, driving them to consume more.
Trouble is, some modern habits exacerbate this biology. Daytime dieting, for instance, magnifies that 8 p.m. urge, causing people to give in and binge. Even nondieters often undereat during the day only to overeat at night, thanks to skipped breakfasts, stress, and high-calorie snacks, says Yoni Freedhoff, M.D., of the Bariatric Medical Institute in Ottawa, Ontario.
But what's the big deal? It turns out that for everyone—whether or not they're overweight—it's not just what you eat that's important, but whenyou eat. Sure, nighttime eating can cause your weight to creep up—but it can also put your overall health at risk.
Eating on Autopilot
It's not so shocking that hoovering food after dark is consistently associated with weight gain and obesity, per both the International Journal of Obesityand the American Journal of Clinical Nutrition. Your activity levels drop in the evening, leaving you less able to burn off surplus calories.
Some studies show that eating lots at night also tamps down your body's production of two key chemicals: melatonin and leptin. The first, a sleep hormone, is what makes you drowsy come bedtime; lower levels leave you more alert. At the same time, reduced levels of leptin, a satiety hormone, mean your brain isn't getting the message that you're full. In other words, the more you eat, the less you sleep. And the less you sleep, the more likely you are to reach for another snack (and another!). When extended, this cycle can lead to sleep deprivation or, eventually, anxiety, depression, or cognitive decline.
Perhaps more alarming is the way p.m. scarfing affects your levels of insulin, the hormone that helps cells pull sugar out of your bloodstream to use as energy. As the sun sets, your body starts to power down for the night, which makes cells more resistant to insulin's effects, according to a new study in Current Biology. So if you've just taken down a hefty after-hours meal, you likely now have high blood sugar (long-term, a diabetes risk factor). Even worse, your body tends to store excess sugar as fat—and larger fat stores only increase insulin resistance, putting you at higher risk for diabetes, not to mention heart disease.
Surprisingly, the first step isn't cutting out all late-night fare, says Deborah Beck Busis, of the Beck Institute near Philadelphia. Rather, it's to amp up your daytime food intake. More-balanced meals will reprogram your body to crave less food at night (yes, even despite that innate urge).
"The key is to be actively in control of your choices," says Freedhoff. Start with a breakfast of at least 400 calories, including 25 grams of protein (e.g., scrambled eggs with feta cheese and spinach). Research shows that eating more in the a.m. decreases your overall intake for the day—the exact opposite of night-eating's effects.
Lunch should also be at least 400 calories with 25 grams of protein. If you get hungry between meals, feel free to nibble, says Busis. Look for 100- to 150-calorie snacks with seven grams of protein. At dinner, stick to that 400-calories-per-meal ideal.
Aside from better food planning, hitting the hay is your best defense. Research shows that people who go to bed after midnight take in 500 extra evening calories. So switch off your TV or tablet early; staring at a screen can spur mindless munching.
You may not be able to break a night-eating habit right away, and that's OK. Just consuming fewer calories at or after dinner will give your body a break and put you on a healthier path.