HIIT Workouts May Promote Fat Loss, Preserve Muscle for People Over 65

High-intensity interval training, commonly known as HIIT, may be worth it for healthy older adults. The new research, published in the journal Maturities in December found that, compared to less intense forms of exercise, HIIT workouts can help reduce body fat percentage and preserve muscle mass in people over 65.

“When appropriate and feasible, higher intensity exercise training may be considered to support improvements in health-related body composition in older adults,” the researchers concluded.

As people age, two changes typically occur that increase the risk of chronic disease: body fat increases and muscle mass decreases, said study lead author Grace Rose, PhD, an exercise physiologist and senior lecturer at the University of the Sunshine Coast in Queensland, Australia.

Exercise can help counteract both of these effects, but Rose noted that little research has focused on exercise outcomes in older adults. “Most of the evidence on exercise intensity comes from younger or sick populations,” she said. “I wanted to understand how different exercise intensities affect body composition, particularly in healthy older adults.”

To explore this, Rose and colleagues recruited 123 healthy men and women aged 65 to 85 to participate in three 45-minute exercise sessions per week for six months. Participants were randomly assigned to one of three groups:

• HIIT: Four 4-minute intervals of varied exercises performed at 85% to 95% of their maximum heart rate, with three minutes of recovery between intervals, ending with a 5-minute cooldown. HIIT workouts typically consist of short sets of exercises like burpees, kneeling jumps, squats, and mountain climbers.
• Moderate-level exercise on a treadmill: A 30-minute continuous treadmill workout in which participants reach 60-70% of their maximum heart rate.
• Low-intensity exercise: A 45-minute stretching and balance class, during which participants reach 45% to 55% of their maximum heart rate.

All participants wore heart rate monitors during exercise and were instructed not to change their diet during the six-month study period and to continue taking their medications regularly. At three and six months, researchers measured participants’ body composition using dual-energy X-ray absorptiometry (DEXA) scans.

On average, the HIIT and moderate-intensity groups lost similar amounts of fat mass. However, the researchers found that the HIIT group experienced the greatest reduction in overall body fat percentage. Notably, the HIIT participants also retained the most muscle, a result that “stood out,” Rose said.

That said, the researchers stressed that the “changes were minimal.” Although the results may have been clinically meaningful for some people, they did not meet this threshold on average.

Additional research is needed to confirm the potential effects of these exercises and to inform clinical recommendations, the researchers concluded.

HIIT can be a great option for older adults, but it’s not the only way to improve your fitness, according to exercise physiologist Jason Machowsky, MS, RD, CSSD.

As research suggests, moderate- and high-intensity workouts can promote weight management and fat loss, he said. To preserve muscle mass, strength training can be “very effective.” Although HIIT is not considered traditional strength training, it often incorporates strength-based movements like push-ups and lunges.

Still, as Machowsky pointed out, HIIT isn’t for everyone. For some people, this can “irritate sensitive joints,” especially if they jump into it too quickly. HIIT may also increase the risk of serious cardiac events, especially in people with pre-existing conditions such as diabetes.

For anyone interested in HIIT, Machowsky recommends first speaking with a doctor or qualified exercise professional, such as a certified exercise physiologist (CEP). He added that it’s also important to increase the intensity gradually so you can monitor how your body responds.