Both time-restricted eating (TRE) and high-intensity interval training (HIIT) have been shown to improve cardiometabolic health in people who are overweight and at risk of serious disease. (Cardiometabolic risk factors affect both heart disease and metabolic disorders such as type 2 diabetes.)
Now a new randomized controlled trial has tested whether combining these two approaches is more effective than either of them on their own.
The results revealed that the combination improved long-term blood sugar control. It also led to a 2-fold greater body fat reduction compared with each intervention in isolation.
About the study
The trial, conducted by researchers from the Norwegian University of Science and Technology had four arms: HIT alone, TRE alone, the TRE-HIIT combination and a control group.
A total of 131 women were enrolled. All of them had overweight or obesity and had risk factors for type 2 diabetes and/or cardiovascular disease.
TRE was defined as consuming all daily calories within a 10-hour time window. HIIT was defined as exercise done at 90% of maximum heart rate for 35 minutes, three times per week. The exercise sessions were supervised by the investigators. The participants were also asked to log their first and last calories every day.
The interventions lasted for 7 weeks. Participants' blood pressure, body mass index, body fat, blood cholesterol, blood glucose and insulin levels were measured before and after the study.
Improvements in HbA1c, body fat, visceral fat with TRE+HIIT
The researchers found that the participants who combined TRE and HIIT were able to improve their long-term glycemic control measured as hemoglobin A1c (HbA1c). They were also able to reduce body fat and visceral fat as well as increase their cardiorespiratory fitness measured as peak oxygen uptake.
There were no differences in blood cholesterol, appetite hormones of blood pressure after any of the interventions compared with the control group.
The researchers recommend this kind of program for people who want a relatively simple way of changing diet and exercise habits and improving their health. Moholdt says. TRE is a less tedious and time-efficient way to lose weight compared with daily calorie counting. HIIT is safe for previously sedentary individuals and can be completed within 30-40 minutes.
A limitation of the study was that the intervention period was only 7 weeks; longer-term investigations are needed to determine effects and feasibility for longer periods of time. The study also took place during COVID-19 lockdowns, which affected the participants' lifestyles and could have influenced the results.
The researchers are currently inviting the participants back for follow-up testing 2 years after they completed the study to find out if they have continued with the interventions. They also plan to determine whether the combination of TRE and HIT will induce the same health benefits and have equally good adherence rates in a completely home-based setting. That study will include both men and women.
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