Intense exercise with time-restricted eating produces health benefits

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Experts say intermittent fasting along with intense exercise provides significant health benefits. Design by MNT; Charles Gullung/Getty Images & zeljkosantrac/Getty Images
  • Researchers report that combining time-restricting eating with intense exercise can get better results than doing either one alone.
  • They said people who combined the diet and exercise routines saw more pronounced changes in body composition and cardiometabolic parameters than people who did only diet or exercise.
  • Experts say that this combination of diet and exercise isn’t necessarily beneficial for everyone.

There’s good news for those who watch the clock before eating and also like intense exercise.

Researchers from the University of Sfax in Tunisia released a study today saying that combining time-restricted eating with high-intensity functional training may improve body composition and cardiometabolic parameters more than either practice alone.

Published in the open-access journal PLOS ONE by a team led by scientists Rania Ameur and Rami Maaloul, the research reenforces much of what is already known about time-restricted eating and intense training.

However, much of that research focused on either time-restricted diets or heavy exercise.

In a press release, the study authors say that “changes in diet and exercise are well-known ways to lose weight and improve cardiometabolic health. However, finding the right combination of lifestyle changes to produce sustainable results can be challenging.”

They explain that time-restricted eating limits when but not what individuals eat. High-intensity functional training combines intense aerobic and resistance exercise.

Experts note that doing either may be beneficial and easier for people to commit to over a significant time period.

In the new study, however, the research team investigated the impact of combining both practices on body composition and markers of cardiometabolic health, such as blood glucose, cholesterol, and lipid levels.

The researchers 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).

The participants following only the time-restricted eating regimen ate only between 8 a.m. and 4 p.m. Subjects in the functional training groups worked out three days a week with an instructor.

All three groups experienced significant weight loss and decreases in waist and hip circumference after 12 weeks. All three groups also showed positive changes in glucose and lipid levels.

But there were differences between the groups.

Researchers said there were improvements observed in fat-free mass (a combination of lean mass and skeletal muscle mass) and blood pressure among those in the diet and exercise group as well as the exercise groups. However, those improvements weren’t seen in the diet-only group.

Subjects in the diet and exercise group generally saw more pronounced changes in body composition and cardiometabolic parameters than either diet or exercise alone groups.

The research team noted it was a relatively small study and it was “difficult to tease out the contributions of specific exercise routines or of time-restricted eating and calorie reduction since both groups reduced their calorie intake.”

They also noted that combining time-restricted eating with high-intensity functional training could show promise in improved body composition and cardiometabolic health.

“Combining time-restricted eating with high intensity functional training is a promising strategy to improve body composition and cardiometabolic health,” the study authors said.

Dr. Mir Ali, a bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in California, told Medical News Today that combining both approaches accelerates fat burning.

“Periods of fasting force the body to burn calorie reserves – fat, after immediate reserves are consumed – and intense physical activity also burns fat,” Ali, who was not involved in the study, said. “Time of eating can affect a person’s weight. Consuming a larger number of calories later in the day can leave less time for a body to metabolize calories, as there is less calorie consumption when you sleep.”

Ali said there’s no set time of day to restrict eating.

“There are certain health conditions where a person may need to eat more regularly throughout the day – such as diabetes – so it’s best for a person to check with their doctor before beginning a time restricted eating routine,” Ali said.

Ryan Glatt, a senior brain health coach and director of the FitBrain Program at Pacific Neuroscience Institute in California, told Medical News Today that combining both practices enhances metabolic efficiency and improves body composition.

But the evidence isn’t uniformly strong across all studies.

“Although more research is needed, it’s believed that eating in alignment with circadian rhythms might enhance metabolism, although the ideal timing for meals can vary based on individual lifestyle and metabolic differences,” Glatt, who wasn’t involved in the study, said.

He added that some people believe working out in the morning or early afternoon could align with circadian rhythms for better results.

“The most effective time depends on personal preferences and daily schedules,” Glatt said. “Previous research has demonstrated that time of day may not matter for exercise, and the desired adaptation may change the ideal time of day to exercise.”

Glatt also said there are people who probably shouldn’t practice time-restricted eating.

“Individuals with certain conditions, such as advanced diabetes, pregnant women, or those with a history of eating disorders, should approach time-restricted eating with caution and seek advice from health professionals,” he said.

Catherine Rall, a registered dietician in Denver, Colorado, told Medical News Today there are other potential negative effects.

“One of its drawbacks is that it can be tough on the heart and other body systems, and it can lead to poor overall nutrition from people who focus on the time-restriction aspect of their diet without considering what they’re eating,” Rall, who wasn’t involved in the study, said. “Adding intense workouts can help improve cardiovascular health and also help the body metabolize that glut of calories that can come during the eating window.”

Marc Massad, a certified athletic trainer based in Dubai, told Medical News Today the study affirms what many of his clients already practice.

“When time-restricted eating is paired with high-intensity sessions, a few noteworthy benefits arise,” Massad, who wasn’t involved in the study, said. “These include improved athletic performance as the body learns to utilize fat for energy, increased resilience to muscle and oxidative damage, and significant enhancements in sleep quality.”

Massad said he’s had clients report that they’ve experienced better digestion and higher levels of mental acuity when sticking to the regimen.

“For seniors – one of my focus populations – coupling these strategies can also boost muscle retention and strength, an important aspect as age progresses,” Massad said. “These potentials make the combination an efficient and holistic approach to health, fitness and sports training.”

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