Time-Restricted Eating, High-Intensity Training Have Heart Benefits for Obese Women

Time-restricted eating (TRE) with a feeding window early in the day and high-intensity functional training (HIFT), when combined, have substantial beneficial effects on body composition and cardiometabolic risk in younger women with obesity who are otherwise relatively healthy, a small trial shows.

Although the two interventions individually had positive effects on health during a 12-week period, greater gains generally were observed among women who participated in both TRE and HIFT, researchers led by Ranya Ameur and Rami Maaloul (University of Sfax, Tunisia), report in a study published online recently in PLOS ONE.

Participants in the combination group, for instance, saw greater reductions in waist and hip circumference, as well as fat mass, compared with those in the either of the trial’s other two arms. Similar patterns were seen for some of the cardiometabolic biomarkers measured in the study.

“In inactive women with obesity, combining TRE with HIFT can be a good strategy to induce superior effects on body composition, lipid profile, and glucose regulation compared with either diet or exercise intervention alone,” the investigators conclude.

Commenting for TCTMD, Michael Wilkinson, MD (Sulpizio Cardiovascular Center at UC San Diego Health, CA), said improvements in certain aspects of health—like body weight or levels of cardiometabolic biomarkers—would be expected with TRE or physical activity. “What’s notable is the effect that was seen across all three arms of this study,” Wilkinson emphasized.

Also noteworthy, he said, is that there was no loss of fat-free mass in the TRE group, a possible concern with these types of eating patterns.

Wilkinson, asked about which intervention might be expected to provide the greater benefit for patients, said, “It is likely that an ideal approach to promoting cardiometabolic health through lifestyle change includes both optimization of diet, through eating heart-healthy foods, limiting caloric intake, and considering meal timing, plus regular physical activity."

Synergistic Effects

TRE is a type of intermittent fasting in which the interval between the last meal of the day and the first meal of the following day is extended, leaving a specific time period for eating on a daily basis. “TRE has been demonstrated to produce similar improvements in cardiometabolic health . . . as continuous calorie-restriction diets,” Ameur, Maaloul, and colleagues note. “This strategy has gained popularity since it is easy to follow for a longer period of time and does not require people to limit overall food consumption or calculate total daily calorie intake, which may improve adherence.”

Physical activity also contributes to treating obesity, and HIFT—a combination of aerobic and resistance exercises performed with alternating short periods of intense exercise followed by rest/recovery periods—has emerged as an alternative to high-intensity interval training. It’s been shown in prior studies to have health benefits in patients with overweight/obesity and type 2 diabetes, with improvements in cardiometabolic risk factors and insulin sensitivity, according to the authors.

In the current trial, the investigators explored whether combining TRE and HIFT would have synergistic effects when compared with either intervention alone. The study included 64 women ages 18 to 45 (mean 32 years) who had a body mass index (BMI) greater than 30 kg/m² (mean 35 kg/m²) and a waist circumference greater than 80 cm, were able to engage in physical activity, had not participated in a structured training program in the previous 6 months, and maintained a constant weight for 3 months prior to randomization. All were free from diabetes and CVD.

The investigators randomized the women to three groups:

• TRE alone (n = 20): women were instructed to eat between 8 AM and 4 PM each day without any restrictions on quantity or type of food, with water and calorie-free beverages allowed during the fasting period.

• HIFT alone (n = 24): women participated in three sessions per week, with each session including eight sets of functional exercises (both aerobic and resistance) done at self-selected intensity, while maintaining their usual eating schedule.
• TRE plus HIFT (n = 20): women participated in both interventions.

The intervention period lasted 12 weeks, and during that time, participants in all three groups had improvements in body composition and cardiometabolic risk.

For body composition, the researchers saw declines in body weight, BMI, waist and hip circumferences, waist-to-hip ratio, and fat mass in all three groups. Fat-free mass increased in the two arms of the trial that included HIFT, with no change in the TRE group. Body composition tended to improve to a greater extent in the TRE plus HIFT group than in the other two groups, although not all of the differences were statistically significant.

In terms of diet, all groups consumed fewer calories, carbohydrates, and fats by the end of the study period, with a decline in protein intake observed only in the TRE plus HIFT group. Total calorie intake was significantly lower in the combination arm than in the HIFT-only arm, whereas fat intake was reduced to a greater extent in the combination and TRE arms than in the HIFT arm.

Cardiometabolic biomarkers improved during the study as well. Total and LDL-cholesterol levels fell—and HDL-cholesterol levels increased—across groups, with triglycerides declining only in the two groups that included HIFT. The drops in total cholesterol and triglycerides were greater in the combination arm than in the other two groups.

All three arms saw decreases in glucose, insulin, and HOMA-IR, although the combination of TRE and HIFT provided a larger decline in glucose compared with HIFT alone and a greater change in insulin and HOMA-IR versus the other two arms.

For blood pressure, women who participated in HIFT had significant drops in systolic and diastolic readings, but there were no significant changes from baseline in the TRE-only group.

Tailor the Approach

In clinical practice, said Wilkinson, “we should be having a conversation with our patients that involves encouraging them both to incorporate diet change and aspects of diet style as well as some degree of physical activity really in order to optimize their cardiometabolic health and reduce their risk of heart disease.”

Ultimately, what that looks like will vary based on the individual patient’s needs, Wilkinson indicated, pointing out that the early eating window or the three HIFT sessions per week as performed in this study may not work for everybody, particularly over the long term.

“When we implement early time-restricted eating or this particular form of physical activity, or both, we see benefits, so the closer we can get patients in our everyday practice to a lifestyle strategy that models something like this, I think we’re doing the right thing,” Wilkinson said. “But we need to personalize the prescription for healthy lifestyle change during that conversation.”

And there’s more to be learned, he said, highlighting the need for studies with longer follow-up to assess adherence to the interventions; with participants who have additional cardiometabolic risk factors and conditions like metabolic syndrome and type 2 diabetes; and with additional tools for measuring the impact of TRE and other lifestyle interventions on body composition, like dual X-ray absorptiometry.