New research from Australian scientists suggests that high intensity interval training stands alone in helping aging adults shed fat without sacrificing muscle, a distinction that could reshape how older people approach fitness.
A study of over 120 healthy adults averaging 72 years old found that while multiple exercise intensities produced modest fat loss, only HIIT preserved lean muscle mass. The research, published in the journal Maturitas, compared three exercise approaches over a six month period of supervised gym sessions.
"We found that high, medium and low intensity exercises all led to modest fat loss but only HIIT retained lean muscle," said Dr. Grace Rose, an exercise physiologist at the University of the Sunshine Coast who led the work.
The distinction matters because body composition changes directly influence whether older adults develop chronic diseases later in life, Rose explained. As people age, maintaining muscle becomes increasingly critical to overall health and function.
Moderate intensity exercise proved counterintuitive. While it reduced body fat, it also caused a small decline in lean muscle, creating a tradeoff that defeated the purpose of staying fit. Both HIIT and moderate training improved the composition of weight around the midsection, though the researchers noted that low intensity results require further analysis.
The study enrolled participants from the Brisbane region with an average body mass index of 26 kg/m2, considered normal for adults over 65. All completed three gym based exercise sessions weekly throughout the half year trial.
HIIT consisted of short bursts of demanding work, where participants breathed heavily and conversation became difficult, followed by easier recovery periods. The repeated stress on muscles appears to signal the body to preserve tissue rather than discard it.
"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," said Mia Schaumberg, an associate professor of physiology at UniSC and study co author.
The timing of the findings carries particular relevance as people launch fitness commitments in early 2026. The research offers clarity on which training approach actually delivers the health outcomes older adults seek.
The study involved researchers from the university's Healthy Ageing Research Cluster and The University of Queensland.
Author Jessica Williams: "This is the kind of practical, evidence backed finding that should reshape gym routines for anyone over 70, not just the vague promise that exercise is good for you."
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