Study: Combine intermittent fasting with high-intensity exercise to boost health

Improvements in body composition, cardiometabolic health seen among women with obesity.

Combining time-restricted eating with high-intensity exercise may lead to more transformative changes in body composition and cardiometabolic health than either intervention alone, a new study suggests. Photo by Kampus Production/Pexels
Combining time-restricted eating with high-intensity exercise may lead to more transformative changes in body composition and cardiometabolic health than either intervention alone, a new study suggests. Photo by Kampus Production/Pexels

NEW YORK, May 1 (UPI) -- Among inactive women with obesity, combining time-restricted eating with high-intensity exercise may lead to more transformative changes in body composition and cardiometabolic health than either intervention alone, a new study suggests.

Cardiometabolic health is comprised of fat mass, insulin sensitivity, glucose, lipid profile and blood pressure.


The findings of the study, conducted at the University of Sfax in Tunisia, were published Wednesday in PLOS ONE.

"Obesity is a critical clinical and public health issue, as it is associated with an increased risk of cardiovascular disease, insulin resistance, cancer, oxidative stress and osteoarthritis," the study's authors wrote.

Changes in diet and exercise are established approaches to losing weight and improving cardiometabolic health. However, it can be challenging to find the right combination of lifestyle modifications that achieve sustainable results, the researchers noted.

Previous studies indicate that time-restricted eating, which limits when, but not what, individuals eat, and high-intensity functional training, which incorporates intense aerobic and resistance exercise, may benefit people and make it easier to commit to a long-term regimen.


"We can highlight in this study that time-restricted eating is a good solution to combat obesity, easy to implement since it does not require people to limit their overall food intake or count the total number of daily calories," the study's corresponding author, Rami Maaloul, said in an interview published by PLOS One.

"In addition, sport has a fundamental role in preventing weight gain," said Maaloul, a researcher in exercise physiology and biochemistry at the University of Sfax in Tunisia.

He noted that with high-intensity functional training, people can "have fun while doing quick exercises and workouts in the gym. It is a serious sport, flexible, and can adapt to individual fitness levels and abilities to help people improve their health and lose weight."

Maaloul added that "if you pair exercise with dieting, you'll lose more weight than if you just dieted alone. So, for optimal benefits you should incorporate both time-restricted eating and high-intensity functional training into your strategy."

For people who don't know how to exercise and are interested in high-intensity functional training, Maaloul, who has a doctorate in the sciences of physical activities and sports, recommends seeking a qualified trainer and slowly picking up the pace.

He also advises obtaining a physical before beginning a new exercise plan.


In this study, Maaloul and his collaborators assigned 64 women with obesity to one of three groups: time-restricted eating (diet only), high-intensity functional training (exercise only) or time-restricted eating plus high-intensity functional training (diet and exercise).

Participants adhering to the time-restricted eating regimen ate only between 8 a.m. and 4 p.m. Those in the functional training groups exercised three days per week with an instructor.

After 12 weeks, all three groups had substantial weight loss and reductions in waist and hip circumference, as well as positive changes in lipid and glucose levels.

However, some differences existed between groups. For example, fat-free mass -- a combination of lean mass and skeletal muscle mass -- and blood pressure improved in the diet-and-exercise and exercise groups, but remained the same in the diet-only group.

Participants in the diet-and-exercise group generally experienced more profound changes in body composition and cardiometabolic parameters than either diet or exercise alone.

The researchers noted that this is a relatively small study, and it is difficult to tease out the contributions of specific exercise routines or of time-restricted eating and calorie reduction, since both groups lowered their calorie intake.

However, they said that combining time-restricted eating with high-intensity functional training may show promise as a strategy in improving body composition and cardiometabolic health.


"Disciplined eating and exercise habits work synergistically to improve one's health status," said Dr. Nauman Mushtaq, medical director of cardiology with the Bluhm Cardiovascular Institute at Northwestern Medicine Central DuPage Hospital in Winfield, Ill. He was not involved in the study.

"It is difficult to come up with specific recommendations based on just one small study, but it does affirm the value of 'walk more, eat less' advice, Mushtaq said.

However, the researchers showed that people who exercised and dieted were able to maintain more muscle mass and lose more fat, said Dr. Hans Schmidt, chief of bariatric surgery and director of the Center for Weight Loss and Metabolic Health at Hackensack University Medical Center in Hackensack, N.J.

"That is significant because it reinforces that this combination provides the necessary stimulus and building blocks for muscle growth and repair, leading to a stronger, more toned physique than, say, dieting alone," Schmidt said.

The combination also improves overall health by lowering blood pressure and cholesterol levels. As a result, it reduces the risk of developing chronic diseases such as heart disease, stroke and type 2 diabetes, he said.

To stick with intermittent fasting, Schmidt recommends starting with a shorter time window, like 12 hours, and gradually increasing it. As for exercise, he suggests a program with a finite amount of time and a support group to help with motivation.


Finding a mobile app with enjoyable high-intensity exercise classes is another option, while staying on a healthy diet, said Dana Ellis Hunnes, a senior clinical dietitian at UCLA Health in Los Angeles.

She said the study's findings seem obvious based on her 20 years' experience as a clinical dietitian and exercise enthusiast who taught a cycling class.

Meanwhile, they also strengthen the argument for combining physical activity, especially high-intensity functional training, with dietary interventions that may include time-restricted eating.

"I found this study to be very compelling and promising," said Hunnes, who has a doctorate in community health sciences and also is an assistant professor at UCLA Fielding School of Public Health. "I'd love to see this replicated in a larger study population."

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