Unlike previous research, the study specifically focused on participants who are obese. Twenty-three individuals, who on average were age 45 and had a body mass index (BMI) of 35, were included. For 12 weeks, the participants were instructed to eat anything they wanted, but only between the hours of 10 a.m. and 6 p.m. Outside of those hours, they were told to consume only water or calorie-free beverages such as black tea or coffee. The diet is called “16:8,” which refers to the number of hours you fast versus the number of hours you eat. “The most surprising result we found is even though we told them they could eat whatever they wanted, they had a natural calorie restriction of about 350 calories per day [compared with the control group],” says the lead study author, Kelsey Gabel, RD, a PhD candidate at the University of Illinois at Chicago. Put differently, although researchers didn’t tell participants on the 16:8 diet to limit their caloric intake, on average, they ended up taking in about 350 calories less per day simply by restricting the window of time during which they ate. RELATED: The Weight-Loss Programs to Try and the Fad Diets to Skip if You Want Results Participants also shed 3 percent of their body weight and had a 7 percent drop in systolic blood pressure. Fat mass, insulin resistance, and cholesterol were also measured, but these markers didn’t vary between the 16:8 diet group and the control group. “I think the [16:8 diet] is something people can do for the long term,” says Gabel. “When people stopped eating all day, I think they became more in tune with their feeding and hunger cues, and stopped eating when they weren’t hungry.” Another small study, published May 10, 2018, in the journal Cell Metabolism found that early time-restricted feeding lowers the desire to eat in the evening and may also improve health, even if the person doesn’t lose weight.
Who Shouldn’t Try Fasting Diets Like 16:8?
Ali Miller, RD, CDE, an integrative dietitian who was not involved in the study but uses the diet (during a different time window, 12 p.m. to 8 p.m.) in her Houston-based virtual practice, agrees with Gabel that 16:8 is more of a lifestyle change than a temporary diet. But she warns that some people who are considering this lifestyle should proceed with caution. “If someone is on a very high carbohydrate diet going into the 16:8 approach, they will have higher insulin levels, so they will likely be a candidate for hypoglycemia (low blood sugar),” says Miller. “Same with diabetics who are unmanaged or on high medication, and people who are on diuretic drugs.” The 16:8 approach is not necessarily off-limits for those individuals, she says, but she recommends they work with a health practitioner for medical monitoring to reduce their medication and maintain the lifestyle. RELATED: Is Intermittent Fasting Safe for People With Diabetes? Although the current study findings are promising, especially for individuals hoping to lose weight or lower blood pressure without counting calories, it’s important to be aware of the small sample size. Another limitation of this research is that the subjects’ dietary intake and adherence to the set time frame were self-reported, which means the calorie deficit noted in the paper could be inaccurate. In the future, Gabel wants to further explore the optimal time frame for the feeding window. People are more insulin resistant as the day goes on, so she’s curious if it’d be more beneficial to have the eating window closer to wake-up time. She’s also interested in finding out whether, if the food window is decreased, patients lose more weight, or perhaps adhere to the diet less closely. RELATED: What a Fasting Diet Can and Can’t Do for Your Health
