Every year, 45 million American adults go on a diet. That’s not surprising when you consider that 180 million American adults—70 percent of us—are overweight or obese. But no matter which diet you choose—high-protein or high-fiber, low-carb or low-fat, keto or paleo, vegan or carnivore—it’s likely that dieting itself, with all its demands and deprivations, will be a difficult ordeal. It’s equally likely that when you go off your diet, you’ll slowly but surely regain all the weight you lost. It’s estimated that only one in 20 people who lose weight on a diet maintain weight loss long-term.
The good news: Research my colleagues and I have conducted at the University of Illinois shows that there’s a way to lose weight that doesn’t involve dieting. This unique approach to weight loss is called time-restricted eating (TRE). Rather than restricting the foods you can eat, you restrict the times you can eat. On a daily basis, you eat all your food within a limited window of time—for example, between noon and 8 p.m. There are no special foods to emphasize, no “bad” foods to eliminate, and no calories to count. You just eat during fewer hours.
With TRE, you consume fewer calories because you spend less time during the day eating. Research shows that an eating window of eight hours accomplishes a daily reduction of 300 to 500 calories. This research is summarized in a scientific paper in the May 2022 issue of Nature Reviews/Endocrinology.
Studies show that, along with weight loss, TRE produces many health benefits in people who are overweight and obese:
Importantly, TRE does a better job of reducing insulin resistance than calorie restriction. That’s probably because not eating for a stretch of time helps the body know when to release insulin to regulate blood sugar and helps make cells more insulin sensitive.
In fact, in a study being readied for publication, my colleagues and I compared TRE to a calorie-restricted diet in people who had type 2 diabetes for at least 15 years. We found that calorie restriction was ineffective for weight loss and blood sugar control. It hardly worked at all. But TRE helped people with diabetes lose an average of 8 percent of their body weight—one of the most successful studies on weight loss in diabetes ever conducted. Some of the study participants were able to get off their diabetes medication, and some achieved full remission from type 2 diabetes, with A1c levels in the normal range.
Scientific research shows that people who successfully lose weight on a time-restricted diet adopt these simple habits:
Eat between noon and 8 p.m. You can do TRE any time that works for you, but in informal surveys, 95 percent of people who have made a lifestyle of time-restricted eating have chosen noon to 8 p.m. as their eating window. Many studies on time-restricted eating show that this is the time period that most people find preferable. Many study participants tend to dislike a time-restricted eating period of 10 a.m. to 6 p.m., because it’s likely they’ll miss the evening meal—the most social meal of the day. Don’t worry about skipping breakfast, which is sometimes touted as the “the most important meal of the day.” A recent study in BMJ analyzed 13 studies on breakfast and weight loss, involving more than 1,400 people, and found there was no health risk in skipping breakfast—and a slight advantage in losing weight.
You can lose weight eating almost any foods. In my research, we often provided weekly nutritional counseling to study participants, guiding them to increase their intake of fruits, vegetables, and other whole foods. It almost never worked. It is very hard to change dietary patterns, most of which are learned in childhood.
TRE can accomplish weight loss without changing the foods you eat. However, for overall health, it’s still important to try to eat more fruits, vegetables, and whole grains, and less processed foods, sugars, and saturated fats.
