Only one workout helped older adults lose fat and keep muscle

Key points

• A six-month trial of 123 healthy older adults in Greater Brisbane found that high-, moderate- and low-intensity exercise all produced modest fat loss, but only HIIT preserved lean muscle.
• HIIT and moderate-intensity training both improved the composition of fat around the middle, while moderate training also caused a small decline in lean muscle.
• Later 2026 studies and a review of 25 reports involving about 2,818 participants found HIIT benefits cardiovascular fitness but did not establish it as consistently better than moderate exercise.

A study published in Maturitas by researchers at the University of the Sunshine Coast compared three exercise intensities in older adults and found that high-intensity interval training, or HIIT, was the only one that reduced body fat while maintaining lean muscle. The trial involved 123 healthy older adults from the Greater Brisbane region, with an average age of 72 and an average body mass index of about 26kg/m2.

Participants completed three supervised 45-minute gym sessions each week for six months and were assigned to high-intensity intervals, moderate-intensity exercise or a low-intensity comparison group. Body composition was measured at the start, at three months and at six months using a specialized scanning technique.

What the researchers found

Both high- and moderate-intensity training significantly reduced fat mass, with larger improvements than the low-intensity group. However, moderate training also caused a small decline in lean muscle, while HIIT reduced fat without the same decline in lean mass.

The researchers also reported improvements in visceral adipose tissue, the fat stored deep in the abdomen around organs such as the liver and intestines, in both the high- and moderate-intensity groups. The team cautioned that the improvements were relatively small and not clearly clinically meaningful compared with lower intensity exercise.

We found that high, medium and low intensity exercises all led to modest fat loss but only HIIT retained lean muscle

— Dr. Grace Rose

How HIIT may work

Study co-author Mia Schaumberg, an associate professor of physiology at the University of the Sunshine Coast, said the training involved repeated short bursts of very hard exercise alternated with easier recovery periods. She said HIIT likely works better because it puts more stress on the muscles, giving the body a stronger signal to keep muscle tissue.

The scans measured lean tissue rather than muscle strength directly, and lean mass includes muscle as well as other tissues and water. The researchers noted that maintaining muscle becomes increasingly important later in life for physical independence.

Later findings and guidance

A 2026 study in Medicine & Science in Sports & Exercise found that 20 adults aged 61 to 74 who did remotely supervised HIIT at home lost an average of about 1.4 kilograms of fat mass over eight weeks and improved aerobic fitness. A separate 2026 trial in older adults living with HIV found no statistically significant difference in body composition changes between HIIT and continuous moderate-intensity exercise when both groups also did resistance training.

A review published in the Journal of Clinical Medicine in August 2026 examined 25 reports involving about 2,818 participants and found the most consistent benefits involved cardiovascular fitness, but did not establish HIIT as consistently better than moderate-intensity exercise. The CDC recommends that adults over 65 combine aerobic exercise, muscle strengthening and balance exercises.