- Previous studies have shown that time-restricted eating (TRE) and high-intensity interval training (HIIT) alone can reduce cardiometabolic risk in people who are overweight or obese.
- A recent randomized controlled trial showed that a 7-week ERT regimen combined with HIIT resulted in greater improvements in long-term glycemic control and body composition in overweight/obese women, compared with TRE or HIIT alone.
- These results suggest that combining TRE and HIIT could be a potential long-term strategy to improve cardiometabolic health in overweight/obese women.
People with obesity and insulin resistance are at increased risk for cardiometabolic conditions, including diabetes, high blood pressure, and other cardiovascular diseases. Lifestyle interventions involving dietary modifications and increased physical activity levels can reduce cardiometabolic risk, but meeting these prescriptions is often challenging.
A new study published in Cellular metabolism suggests that overweight/obese women who followed a regimen of time-restricted feeding (TRE) combined with high intensity interval training (HIIT) over seven weeks showed greater improvements in metabolic health than either intervention alone.
Furthermore, these participants showed high levels of adherence to TRE and HIIT alone and in combination.
study co-author Dr. Trine Moholdtexercise physiology researcher at the Norwegian University of Science and Technology, said:
“Our findings of improved body composition, metabolic health, and high compliance rates suggest that women at high risk for cardiometabolic disorders can improve their health with a combined TRE + HIIT program and that it is safe and feasible for this population.”
Strategies for losing and maintaining weight primarily involve increased physical activity and dietary changes. However, studies have shown that weight loss strategies like reduce daily caloric intake and meeting recommended levels of physical activity are associated with low levels of adherence.
This has led to an increase in interest in alternative weight loss strategies such as TRE and HIIT.
Time-restricted eating involves restricting your intake of calorie-containing foods to a specific period of time, usually between 6 and 12 hours, during the day.
TRE does not limit the types of food that can be eaten or the calorie intake during the eating window. This could promote better compliance than the standard weight loss strategy of calorie restriction.
“ERT offers a relatively simple method of changing dietary habits by focusing solely on meal timing and typically induces a spontaneous reduction in energy intake without deliberate effort,” said Dr. Moholdt.
High-intensity interval training, on the other hand, involves short, repeated bouts of high-intensity exercise interspersed with periods of rest or low-intensity activity.
Around 80% of adults in the United States do not meet current physical activity guidelines that recommend moderate-intensity aerobic exercise for 150 minutes per week. HIIT requires a significantly lower time commitment and produces greater than improvements in cardiorespiratory fitness than moderate-intensity training. Therefore, HIIT can be a viable and time-efficient strategy for weight loss.
Previous studies have shown that TRE and HIIT alone can improve cardiovascular Y metabolic health in people at risk of cardiometabolic disorders. Furthermore, a combination of TRE and HIIT It has been shown to facilitate weight loss and reduce body fat levels in trained athletes.
However, evidence on the effects of a combination of TRE and HIIT in people with obesity who have a more sedentary lifestyle is lacking.
In the current randomized controlled trial, investigators examined the combined effect of time-restricted eating and HIIT in overweight/obese women of reproductive age.
The researchers randomly assigned the 131 overweight/obese women enrolled in the study to one of four groups: combined TRE and HIIT, TRE alone, HIIT alone, and the no-intervention control group. HIIT involved three treadmill exercise sessions per week that were supervised by the researchers, while TRE involved restricting calorie intake to a 10-hour window during the day.
These interventions lasted a total of seven weeks and the participants were given a series of assessments to assess glycemic control and cardiometabolic health before and at the end of the intervention.
The primary evaluation included the glucose tolerance test, which measures the body’s ability to absorb glucose. The researchers also assessed cardiorespiratory fitness and other metabolic markers of glucose metabolism and regulation, body composition, and blood lipid profile at baseline and after the study.
The researchers found that participants in TRE and HITT alone and combined showed no difference in glucose tolerance compared to the control group.
However, participants in the combined TRE and HITT group showed a greater reduction in levels of glycosylated hemoglobin, a measure of long-term glycemic control, than any intervention alone. Glycosylated hemoglobin refers to the hemoglobin in red blood cells bound to glucose and reflects blood glucose levels over the previous 2-3 months.
All three interventions resulted in lower body weight and higher total and visceral fat mass loss than the control group without intervention.
Furthermore, the combined TRE and HIIT group showed a two-fold decrease in total and visceral fat mass than the TRE and HIIT group alone. This is noteworthy since visceral fat, the fat that surrounds the abdominal organs, is a risk factor for diabetes and other metabolic diseases.
The researchers then examined levels of adherence to these interventions over the seven-week study period. Individuals in the TRE alone and combined TRE and HIIT groups adhered to the 10-hour eating window for an average of more than six days per week during the study.
Similarly, participants in the HIIT alone and combined TRE and HIIT groups completed more than 90% of exercise sessions. The researchers cautioned that more research is needed to determine whether such high rates of HIIT adherence can be sustained over a longer period.
“We believe that the high adherence rates reported in our study were due to the close follow-up of the participants and the fully supervised exercise sessions. In most real-world settings, such follow-up is neither realistic nor available,” explained Dr. Moholdt.
This study is one of the largest studies to examine the combined impact of TRE and HIIT. However, the study had some limitations.
The short study duration of seven weeks might not have been sufficient to detect differences in metabolic markers of health and measures of glycemic control due to the three interventions.
Dr Courtey Petersonassociate professor in the Department of Nutritional Sciences at the University of Alabama at Birmingham, said:
“The study lasted only seven weeks, so that may not be enough time to see changes in health, and the study included only women. There is some suggestive evidence that intermittent fasting has slightly different effects in men and women, so we don’t know if the same is true in men. Also, the study is not large enough to detect all possible health improvements. Lastly, the body fat that was being measured was not measured using bioimpedance, which is not the best available test for measuring body fat.”
study co-author Dr John Hawleydirector of the Exercise and Nutrition Research Program at Australian Catholic University, Melbourne, agreed with Dr Peterson’s comments that the study only includes women and said it needs to be replicated in men.
“The ERT participants reported eating less, so we don’t know if the positive effects of ERT were due to lower energy intake or the timing of the meals themselves,” added Dr. Hawley.
Researchers are currently conducting studies to further examine the impact of TRE combined with HIIT and address some of the shortcomings of their current work.
“Further research should investigate the long-term effects of these interventions and their combination. Furthermore, we believe that the high adherence rates reported in our study were due to the close follow-up of the participants and the fully supervised exercise sessions. In most real-world environments, such tracking is neither realistic nor available. We are now investigating whether TRE combined with HIIT performed remotely for seven weeks will induce positive health benefits in overweight or obese men and women,” said Dr. Moholdt.
“Currently, we are also inviting women who participated in the study to undergo further laboratory tests and complete questionnaires about adherence and perceptions of TRE and/or HIIT two years after they have completed the intervention period,” he added.
“[A] The two-year follow-up study will give us insight into how TRE and HIIT can be maintained after a familiarization period provided through a study setting, and whether the health benefits initially induced by the interventions are sustained long-term. term”.
— Dr. Trine Moholdt
