Paleo shuns grains. Following keto? Forget carbs. Most weight-loss strategies involve rules about what foods, or at least how much, you’re consuming.
But altering when you eat instead could also help you shed pounds. That’s according to a small new study from Krista Varady, Ph.D., associate professor of kinesiology and nutrition and director of the Metabolic Kitchen at the University of Illinois Chicago.
Varady has been studying different forms of intermittent fasting—in other words, alternating between periods of eating and not eating—for more than a decade. Eating less, or counting calories, doesn’t come easily for many people, she says. “So I’ve been approaching it from different angles, trying to find other methods to help people lose weight.”
The new study involves something called the 16:8 diet. On it, Varady and her research team gave 23 obese men and women just one rule: to eat only between 10 a.m. and 6 p.m. During those eight hours, no foods were off limits. For the other 16, they were limited to calorie-free beverages like water, tea, coffee, and diet soda.
Despite not having to track, weigh, or measure foods, the participants naturally ate less—to the tune of about 350 calories, according to findings published in the journal Nutrition and Healthy Aging. As a result, they lost about 3 percent more weight than a control group of people who didn’t change their eating habits, and also lowered their blood pressure.
The results were more modest than another type of intermittent fasting Varady’s studied, called alternate day fasting. On that plan—as she outlines in her book on the topic, The Every-Other-Day Diet—you strictly limit yourself to 500 calories one day, then eat whatever you want the next. Repeat, and her research shows an average of 6 percent weight loss over a year. (Over time, some studies even suggest fasting might reduce the risk of diseases like cancer.)
Though you might not lose weight as quickly on the 16:8 diet, many people might find it easier to start—and, most importantly, to maintain. “The fact that you could have breakfast, lunch and an earlier dinner is appealing and also sustainable,” says Chicago dietitian Vicki Shanta Retelny, R.D.N. “It’s a lifestyle approach that people can embrace for a long period of time or even for a lifetime.”
More research is needed to understand the long-term effects of this approach, note Retelny and Varady (who’s hoping to secure research funding to do it). And it might not mesh with certain people’s biology or lifestyle.
“There is no one diet that’s going to work for everybody,” says Elizabeth Lowden, M.D., bariatric endocrinologist at the Northwestern Medicine Metabolic Health and Surgical Weight Loss Center at Delnor Hospital.
Pregnant women and people with chronic health conditions—especially diseases like diabetes, which requires regular eating to regulate blood sugar—should steer clear of these plans, or at least check with their doctors. Fasting might also trigger unhealthy habits in people who’ve struggled with disordered eating in the past, Lowden notes.
But for otherwise healthy people who like sticking to schedules, the eight-hour-on, 16-off approach offers an alternative to calorie-counting or eliminating food groups. You can move the window around if you want, but aim to stop eating by 8 p.m., Varady says. Stay hydrated, eat plenty of protein, and steer clear of food ads on TV, which can provoke cravings during your fasting hours.
Even if you don’t want to stick strictly to an eight-hour window, you can take some lessons from this plan. Going a little bit longer without eating could reconnect you to your hunger cues, which we all too often ignore in a world of frequent grazing, Varady says.
Plus, most people could likely benefit from eating less late at night, when our metabolisms slow and we’re prone to mindless munching on the couch or in the soft blue glow of screens. You could start with something as simple as not eating for two hours before bedtime, Retelny says: “It doesn’t have to be all or nothing.”
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