Time-restricted eating, which restricts eating to specific hours of the day, does not affect the weight of overweight adults with prediabetes or diabetes. Adults in the American Heart Association's 12-week study ate the same healthy, pre-prepared foods, but one group ate most of their calories before 1 p.m. every day, compared to the other group who ate 50% of their calories after 5 p.m.
"We've long wondered if when someone eats during the day it affects how the body uses and stores energy," said study author Nisa M. Maruthur of Johns Hopkins University in Baltimore. Most previous studies haven't checked calorie count, so it wasn't clear whether people who ate before just ate fewer calories. In this study, we only changed the time of eating.”
Maruthur and colleagues followed 41 overweight adults in a 12-week study. Most participants (90%) were black women with prediabetes or diabetes, and the mean age was 59 years. Twenty-one of the adults followed a time-restricted diet, restricting eating to specific hours of the day and eating 80% of their calories before 1 p.m. The remaining 20 participants ate at normal times over a 12-hour period and consumed half their daily calories after 5 p.m. for the entire 12 weeks. All participants ate the same pre-prepared, healthy meals provided for the study. Weight and blood pressure were measured at the start of the study; then after 4 weeks, 8 weeks and 12 weeks.
The analysis found that people in both groups lost weight and had lower blood pressure, regardless of when they ate.
“We thought the time-bound group would lose more weight,” Maruthur said. “Yet that didn't happen. We saw no difference in weight loss for those who ate the most calories earlier than later in the day. We also did not see any effect on blood pressure.”
The researchers are now collecting more detailed information about blood pressure recorded over 24 hours, and they will pool this information with the results of a study on the effects of time-restricted diets on blood sugar, insulin and other hormones.
“Together, these findings will help us better understand the effects of time-restricted eating on cardiometabolic health,” said Maruthur.
