Losing body fat is one thing. Losing fat while keeping the muscle that helps you stay strong and active is another, especially as you get older. Research suggests that one particular type of exercise may have an advantage when it comes to achieving both goals.
High-intensity interval training (HIIT), which involves alternating short bursts of demanding exercise with easier recovery periods, may be especially helpful for older adults who want to reduce fat without sacrificing lean muscle.
In a study published in Maturitas, researchers from the University of the Sunshine Coast compared three different exercise intensities. Although participants across the groups experienced modest fat loss, HIIT stood out for its ability to reduce fat while maintaining lean tissue.
“We found that high, medium and low intensity exercises all led to modest fat loss but only HIIT retained lean muscle,” said lead author and exercise physiologist Dr. Grace Rose of the University of the Sunshine Coast.
The results highlight an important distinction in healthy aging: losing weight is not necessarily the same as improving body composition.
Six Months of Exercise Revealed a Key Difference
The Australian research team investigated how workout intensity affects body composition, meaning the proportions of fat, muscle and other tissues that make up the body.
A total of 123 healthy older adults from the Greater Brisbane region participated in the trial. Their average age was 72, and their average body mass index was approximately 26kg/m2, which the researchers described as normal for adults over 65.
Participants completed three supervised gym sessions each week for six months. Each session lasted 45 minutes, and participants were assigned to high-intensity intervals, moderate-intensity exercise, or a low-intensity comparison group.
To track changes, researchers measured body composition at the beginning of the study, after three months, and again at six months. They used a specialized scanning technique that estimates fat and lean tissue throughout the body.
The findings revealed that exercise intensity made a difference.
Both high- and moderate-intensity training significantly reduced fat mass, with larger improvements than those seen in the low-intensity group. However, the two more demanding approaches differed in their effects on lean tissue.
“While moderate training reduced fat mass, it also caused a small decline in lean muscle,” Rose said.
Participants performing HIIT, meanwhile, reduced fat without experiencing the same decline in lean mass.
This could be particularly valuable later in life, when maintaining muscle becomes increasingly important for physical independence. Strong muscles help people climb stairs, get out of chairs, maintain balance, and carry out everyday activities.
One important distinction is that the scans measured lean tissue rather than muscle strength directly. Lean mass includes muscle but also other tissues and water, so changes in these measurements do not necessarily translate into equivalent changes in strength.
High-Intensity Exercise Also Reduced Abdominal Fat
The researchers found another potentially important benefit involving fat stored around the middle of the body.
“Both high and moderate intensities improved the composition of weight carried around the middle. Further analysis is needed of the low intensity results.”
The original study found improvements in visceral adipose tissue among both the high and moderate intensity groups.
Visceral fat is different from the fat that sits directly beneath the skin. It accumulates deeper in the abdomen, surrounding internal organs such as the liver and intestines.
Excessive amounts of this fat have been linked to insulin resistance, cardiovascular disease, and other metabolic problems.
According to Rose, these findings matter because body composition can influence the development and progression of chronic diseases as people age.
While body weight and body mass index provide useful general information, they do not reveal how much fat or muscle a person carries, or where that fat is stored.
Someone who loses fat while maintaining muscle may experience a more favorable change in body composition than someone who loses a similar amount of weight along with valuable lean tissue.
Still, the original researchers emphasized that the improvements were relatively small. They cautioned that the differences were not clearly clinically meaningful when compared with lower intensity exercise, particularly after accounting for measurement uncertainty.
Why HIIT May Help Aging Muscles Stay Strong
One possible explanation for HIIT’s advantage lies in the way it challenges the body.
Rather than exercising at the same pace throughout a workout, HIIT repeatedly pushes the cardiovascular system and working muscles through periods of intense effort, followed by easier activity.
University of the Sunshine Coast Associate Professor of Physiology and study co-author Mia Schaumberg explained how the training worked.
“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.
“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.”
This explanation is consistent with the idea that muscles adapt to the demands placed on them. When exercise provides a sufficiently challenging stimulus, the body has more reason to maintain the tissues needed to perform that activity.
Muscle preservation is especially important because aging is often accompanied by a gradual decline in muscle mass and strength. In more advanced cases, this can contribute to sarcopenia, a condition characterized by reduced muscle strength and quantity that can interfere with mobility and independence.
Schaumberg said the original research could help people make more informed decisions about exercise and healthy aging.
When the university publicized the findings in early 2026, she also highlighted their relevance to people setting fitness goals.
“With the festive season now behind most of us and New Year’s resolutions in full swing, this research can help inform people’s plans for healthy aging in 2026,” she said.
The research involved collaborators from UniSC’s Healthy Ageing Research Cluster and The University of Queensland.
More Recent Studies Reveal Additional Benefits of HIIT
Research published in 2026 has provided further insight into how HIIT affects older adults, although it also suggests that intense workouts are not necessarily superior in every situation.
One 2026 study, published in Medicine & Science in Sports & Exercise, investigated whether older adults could benefit from completing HIIT at home with remote supervision.
The study involved 20 adults aged 61 to 74 who exercised using a specialized machine that let them work their arms and legs without bearing their body weight.
After eight weeks of training, participants had lost an average of approximately 1.4 kilograms, or about 3 pounds, of fat mass. Their aerobic fitness also improved substantially.
Participants completed 96 percent of their scheduled workouts, and the researchers reported no exercise-related adverse events.
Although the trial was small, its findings suggest that appropriately supervised HIIT programs may offer benefits outside a conventional gym.
Another 2026 randomized trial, published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences, compared HIIT with continuous moderate-intensity exercise in older adults living with HIV.
In that study, participants completed 16 weeks of exercise, with both groups also performing resistance training.
Unlike the original Australian study, both exercise groups experienced reductions in fat and increases in lean mass. The researchers found no statistically significant difference between the two groups in those body composition changes.
These results suggest that workout intensity is not the only factor that matters. Resistance training, which challenges muscles through weights or other forms of resistance, may also help preserve or increase lean tissue.
The populations and training programs differed, so the findings should not be treated as a direct contradiction of the Australian results.
Is HIIT Really the Best Exercise for Older Adults?
A broader scientific review published in the Journal of Clinical Medicine in August 2026 offers additional perspective.
Researchers examined 25 reports involving approximately 2,818 participants to assess how HIIT and other forms of interval training affect older adults.
The most consistent benefits involved cardiovascular fitness, including improvements in the body’s ability to use oxygen during exercise.
Some studies also reported improvements in physical function and metabolic health. However, the review did not establish that HIIT was consistently better than moderate-intensity exercise.
The researchers noted that differences between exercise programs, participant characteristics, and study methods made it difficult to identify a single optimal training approach.
Taken together, the findings suggest that HIIT can be a useful tool for healthy aging, but it is not the only way to improve fitness or protect muscle.
For adults over 65, the Centers for Disease Control and Prevention recommends a combination of aerobic exercise, muscle strengthening activities, and exercises that improve balance.
Higher intensity workouts may be appropriate for some older adults, but people who are inactive or have medical conditions may benefit from gradually building up their fitness and seeking guidance before beginning a demanding program.
The central message from the Australian study remains compelling: what happens to muscle during fat loss may be just as important as the amount of weight someone loses.
HIIT showed promise because it helped participants reduce body fat while maintaining lean tissue. Combined with newer findings, the research reinforces the value of exercise programs that support not just a lower number on the scale, but also the strength, fitness, and physical function needed for healthy aging.
