Women of reproductive age with obesity and insulin resistance are at increased risk of type 2 diabetes and cardiovascular disease and are also predisposed to adverse pregnancy outcomes, including adiposity and cardiometabolic disorders in their offspring. Time-restricted feeding (TRE) is a popular dietary strategy that emphasizes meal timing consistent with daily circadian rhythms, allowing ad libitum energy intake during a restricted feeding window ( 8-10h between the first and last energy intake of the day).
High-intensity interval training (HIIT) performed as short, repeated sessions of high-intensity aerobic exercise, separated by low-intensity rest, is a time-efficient alternative to current recommendations for higher-volume physical activity and improves cardiorespiratory fitness and insulin sensitivity in high-risk populations
A team from the Research Group on Exercise, Cardiometabolic Health and Reproduction at the Norwegian University of Science and Technology (NTNU) wanted to compare the effects of the combination of TRE and HIIT with their isolated effects and determine whether they would act synergistically in improving health in individuals at risk of cardiometabolic disease. This finding underscores the importance of changing both dietary and physical activity habits for individuals who want to rapidly improve their health and reduce their risk of disease.
The trial had four arms: HIT alone, TRE alone, the TRE-HIIT combination, and a control group. 131 women enrolled. All of them were overweight or obese and had risk factors for cardiometabolic diseases such as type 2 diabetes and cardiovascular disease. The exercise sessions were supervised by the researchers and the participants were asked to record their first and last calories each day.
The interventions lasted seven weeks. Various ex-ante and ex-post measurements were taken, such as the participants’ blood pressure, body mass index, fat and cholesterol levels, and various measurements of blood glucose and insulin.
The researchers found that participants who combined TRE and HIIT improved their mean long-term glycemic control measured as HbA1c. They could also reduce fat mass and visceral fat effectively and increase their cardiorespiratory fitness measured as maximal oxygen consumption. However, there were no statistically significant differences in blood lipids, appetite hormones, or vital signs after any of the interventions compared to the control group.
Another important finding was that adherence to the study was high. Once finished, 18 participants from the control group also decided to try one of the interventions.
Longer-term investigations are needed to determine effects and viability over longer periods. The study also took place during the COVID-19 lockdowns, which affected the lifestyles of the participants and could have influenced the results.
The scientists are inviting the participants to return for follow-up tests two years after completing the study to find out if they have continued with the interventions. They also plan to determine if the combination of TRE and HIT will induce the same health benefits and have equally good adherence rates in a completely home setting.