High-intensity interval training burns as much fat as moderate cardio but preserves muscle mass better, according to researchers at the University of Sunshine Coast in Australia.
The study involved 123 physically active adults with an average age of 72. All had a normal body mass index, but their body fat percentage fell in the overweight range. Participants were divided into three groups: HIIT on a treadmill, moderate-intensity cardio, and balance, stretching and strengthening exercises. Each group trained three times a week for six months.
Both the HIIT and moderate-intensity groups lost roughly the same amount of total and visceral fat, the fat surrounding internal organs that raises the risk of type 2 diabetes and cardiovascular disease. The critical difference was muscle: HIIT participants held on to theirs, while the moderate-intensity group saw a noticeable decline.
The researchers attributed this to HIIT’s stronger stimulation of muscle protein synthesis, the process that repairs and builds muscle tissue.
Exercise physiologist and trainer Timothy Coyle noted that muscle loss accelerates sharply after age 60, making its preservation one of the most important factors for health and independence in older age.
How to Start Safely
For beginners, Coyle recommended the protocol used in the study: four minutes of intense effort followed by three minutes of recovery, repeated four times. He advised against pushing to maximum intensity in the first few weeks, suggesting two to three sessions a week with a gradual increase in effort.
Coyle also noted that high intensity is individual. For some people it means running; for others, a brisk walk or a hill climb qualifies.
People with heart conditions, metabolic disorders or kidney disease should consult a doctor before starting HIIT. Anyone who experiences chest pain, dizziness or severe shortness of breath during a session should stop immediately.
