Older adults may benefit most from HIIT exercise, study suggests

• A study suggests high-intensity interval training (HIIT) can reduce body fat most effectively without compromising muscle mass in older adults.
• Moderate- and low-intensity exercise may also help reduce fat, but might lead to some muscle loss.
• The findings may help tailor exercise recommendations for healthy aging.

Body composition describes the relative proportions of lean body mass (muscles, bones, skin, organs, and water) and body fat mass. Unlike body mass index (BMI), body composition can offer a more precise measure of health and fitness.

Healthcare professionals routinely recommend that older adults engage in regular physical activity to promote health and prevent changes in body composition. However, evidence for which exercises are best for improving body composition among older adults remains sparse, with most research focusing on younger populations.

New research from Australia goes some way toward filling that gap. A study published in Maturitas suggests that high intensity interval training (HIIT) may be the optimal exercise for helping older adults to reduce body fat while preserving muscle mass.

Researchers from the University of the Sunshine Coast examined how different exercise intensities affect body composition in older adults. The observational study involved more than 120 healthy older adults from the Greater Brisbane region, with an average age of 72.

The individuals had an average body mass index (BMI) of 26 kilograms per square meter (kg/m2), which the researchers categorised as normal for people aged over 65.

Participants were assigned to different exercise intensity groups and engaged in structured, supervised exercise programs three times a week for 6 months. The three exercise intensity groups included:

1. HIIT: short bursts of very vigorous activity alternated with recovery periods
2. moderate-intensity training: continuous exercise at a steady, moderate effort
3. low-intensity training: Gentler sessions designed for ease and sustainability.

Participants from all three groups experienced modest reductions in body fat. However, only the HIIT group maintained their lean muscle mass over the 6 months. By contrast, the moderate group showed slight muscle declines, and the effect in the low-intensity group was less clear.

“We found that high, medium and low intensity exercises all led to modest fat loss but only HIIT retained lean muscle,” said study lead author Grace Rose, PhD, of the University of the Sunshine Coast, in a press release.

HIIT is an effective training protocol that alternates short bursts of vigorous activity, performed at 100% effort, with brief, low intensity recovery periods.

The framework is designed for efficiency and forces the body to work anaerobically. This refers to when the body breaks down glucose for energy without using oxygen. Evidence highlights that HIIT can be an effective and safe strategy for improving health.

The researchers suggest that HIIT supports body composition by placing greater stress on muscles, encouraging the body to retain muscle mass.

“High intensity training in this study involved repeated short bursts, or intervals, of very hard exercise — where breathing is heavy and conversation is difficult – alternated with easier recovery periods,” said study co-author Mia Schaumberg, PhD, in a press release.

“HIIT likely works better because it puts more stress on the muscles, giving the body a stronger signal to keep muscle tissue rather than lose it,” added Schaumberg.

The findings of this study add to the growing evidence that exercise intensity plays a key role in longevity and may have more of an impact than the quantity of physical activity.

While all exercise is beneficial, this study indicates that incorporating high intensity intervals into fitness routines might offer older adults a way to combat fat mass gain without sacrificing muscle.

However, while HIIT may offer health benefits, it may not be suitable for everyone. The study generally involved healthy older adults, so results may differ for those with certain health conditions or mobility limitations.

While the results are encouraging, more research is necessary to understand how different exercise types affect long-term health outcomes in diverse aging populations.

Anyone considering a new or more intense exercise regimen should consult a healthcare professional or qualified trainer to help tailor exercise plans to their abilities and health status.