Time-restricted eating reduces weight, HbA1c for adults with type 2 diabetes
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Key takeaways:
- Time-restricted eating, but not calorie restriction, induced a greater weight loss than usual eating habits.
- A greater HbA1c reduction was observed for both time-restricted eating and calorie restriction.
Adults with type 2 diabetes and obesity achieved greater weight loss with time-restricted eating at 6 months than with calorie restriction or continuing usual eating habits, according to study data.
In findings from a randomized controlled trial published in JAMA Network Open, adults were randomly assigned to adhere to 8-hour time-restricted eating, follow a calorie-restricted diet, or continue usual eating and exercise habits. At 6 months, those participating in time-restricted eating had greater reductions in HbA1c and body weight than the control group, whereas calorie restriction was associated with a greater decrease in HbA1c, but not body weight, compared with controls.
“It’s important to give people with type 2 diabetes more than one strategy to lose weight and decrease their HbA1c,” Krista A. Varady, PhD, professor of nutrition at University of Illinois Chicago, told Healio. “Some people find it difficult to count calories. Others don’t have weekly or monthly support, and they need a dietary pattern that is simple to follow, such as watching the clock.”
Varady and colleagues enrolled 75 adults aged 18 to 80 years with type 2 diabetes, an HbA1c between 6.5% and 11% and a BMI between 30 kg/m2 and 50 kg/m2 to participate in the trial (mean age, 55 years; 71% women; 53% non-Hispanic Black; 40% Hispanic). Participants were randomly assigned, 1:1:1, to time-restricted eating, calorie restriction, or usual eating and exercise. The time-restricted eating group ate ad libitum between noon and 8 p.m. each day and fasted the remainder of the day. Adults in the calorie restriction group were instructed to reduce their energy intake by 25% of their baseline energy needs. All participants met with a dietitian weekly for the first 3 months of the trial and then biweekly until 6 months. Body weight, adherence to the prescribed diet, medication use and adverse events were recorded at each appointment meeting. Continuous glucose monitors were worn for 10 days at baseline, 3 months and 6 months. The primary outcome of the trial was the percent change in body weight in each group at 6 months.
Time-restricted eating lowers weight and HbA1c
At 6 months, the time-restricted eating group had a 3.56% greater loss in body weight (P = .004) and a 2.49 kg greater decrease in fat mass compared with the control group. No difference was observed between the calorie restriction group and controls for change in mean body weight and fat mass.
The time-restricted eating group had a 0.91% greater reduction in HbA1c, and the calorie restriction group reduced their HbA1c by 0.94% more than the control group at 6 months. There was no difference in HbA1c change between the time-restricted eating and calorie restriction groups. Adults participating in time-restricted eating lowered their mean glucose by 42.53 mg/dL more than the control group, and those participating in caloric restriction had a 48.55 mg/dL greater decline in mean glucose than controls. No differences were observed for time in range.
“We were surprised that the calorie restriction group did not lose more weight,” Varady said. “In most studies looking at people with obesity, the time-restriction eating and calorie restriction groups lose the same amount of weight. Also, we were surprised that even though this weight loss was different, the HbA1c reduction and mean glucose reduction was the same. This might be because though the two groups lost different amounts of weight, they had similar reductions in their visceral fat and their waist circumference, and possibly that's why their blood sugar improved similarly, even though the weight loss was different on the scale.”
More studies needed
At 6 months, the time-restricted eating group cut their energy intake by 313 kcal per day and the calorie restriction group lowered their energy intake by 197 kcal per day. Adults who participated in time-restricted eating were adherent 87% of days during the trial. Of those in the calorie restriction group, 68% reported being adherent to their prescribed calorie goals during the trial.
No serious adverse events occurred during the trial. There was no difference in hypoglycemia or hyperglycemia events between the groups.
“A lot more research is needed in time-restricted eating in those with diabetes,” Varady said. “It would be interesting to see if reducing the eating window to 6 hours a day changes weight loss and blood sugar outcomes. It would also be interesting to see more trials in individuals on insulin and if time-restricted eating could reduce insulin use.
For more information:
Krista A. Varady, PhD, can be reached at varady@uic.edu.
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