Losing body fat is one thing, but shedding fat while keeping the muscle that helps you stay strong and active is another challenge entirely, especially as you get older. New scientific research suggests that one particular type of exercise may hold a distinct advantage when it comes to achieving both goals simultaneously.
High-intensity interval training, widely known as HIIT, involves alternating short bursts of demanding exercise with easier recovery periods. According to recent findings, this approach may be especially helpful for older adults who want to reduce overall fat without sacrificing valuable lean muscle tissue.
In a study published in the journal Maturitas, researchers from the University of the Sunshine Coast compared three different exercise intensities to see how they affected aging bodies. Although participants across all the study groups experienced modest fat loss over the course of the trial, HIIT stood out uniquely for its ability to reduce fat while actively 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 and often overlooked distinction in the field of healthy aging: losing weight is not necessarily the same thing as improving overall body composition.
Six Months of Exercise Revealed a Key Difference
The Australian research team set out to investigate how varying workout intensity directly affects body composition, which refers to the relative proportions of fat, muscle, bone, and other tissues that make up the human body.
A total of 123 healthy older adults from the Greater Brisbane region participated in the clinical trial. Their average age was 72 years old, and their average body mass index was approximately 26 kilograms per meter squared, a figure that the researchers described as entirely normal for adults over the age of 65.
The participants completed three supervised gym sessions each week for a total duration of six months. Each individual session lasted for 45 minutes. During this time, participants were assigned to one of three groups: high-intensity intervals, moderate-intensity continuous exercise, or a low-intensity comparison group.
To track physical changes accurately over time, the researchers measured body composition at the very beginning of the study, at the three-month mark, and again at the conclusion of the six-month period. They utilized a specialized scanning technique designed to estimate both fat and lean tissue volumes throughout the entire body.
The resulting data revealed that exercise intensity genuinely made a measurable difference in the outcomes.
Both the high-intensity and moderate-intensity training programs significantly reduced fat mass, producing notably larger improvements than those observed in the low-intensity group. However, the two more demanding approaches differed significantly in their secondary effects on lean tissue.
"While moderate training reduced fat mass, it also caused a small decline in lean muscle," Dr. Rose noted.
Participants performing HIIT, on the other hand, successfully reduced their fat mass without experiencing that same undesirable decline in lean mass.
This protective effect could be particularly valuable later in life, when maintaining muscle mass becomes increasingly critical for preserving physical independence. Strong muscles help people perform routine daily tasks, such as climbing stairs, getting out of chairs, maintaining physical balance, and carrying out everyday household activities without assistance.
Researchers noted one important technical distinction: the advanced scans measured lean tissue broadly rather than isolating muscle strength directly. Because lean mass includes muscle along with other bodily tissues and water, changes in these specific measurements do not necessarily translate into exact, equivalent changes in raw physical strength.
High-Intensity Exercise Also Reduced Abdominal Fat
Beyond overall muscle preservation, the researchers uncovered another potentially critical benefit involving the specific type of fat stored around the middle of the body.
"Both high and moderate intensities improved the composition of weight carried aroundgetPackage the middle. Further analysis is needed of the low intensity results," the team reported.
The original study documented measurable improvements in visceral adipose tissue among both the high-intensity and moderate-intensity groups.
Visceral fat is fundamentally different from the subcutaneous fat that sits directly beneath the skin. It accumulates much deeper within the abdominal cavity, closely surrounding internal vital organs such as the liver and the intestines.
Excessive amounts of this deep abdominal fat have long been linked by medical professionals to insulin resistance, cardiovascular disease, and a host of other serious metabolic problems.
According to Dr. Rose, these findings matter immensely because body composition can directly influence the development and progression of chronic diseases as people grow older.
While simple body weight and standard body mass index calculations provide useful general information, they fail to reveal how much actual fat or muscle a person carries, or precisely where that fat is being stored inside the body.
An individual who loses fat while successfully maintaining muscle may experience a far more favorable change in overall body composition than someone who loses a similar amount of weight on a scale along with valuable lean tissue.
Still, the original researchers were careful to emphasize that the physical improvements observed were relatively small. They cautioned that the differences were not necessarily clearly clinically meaningful when compared directly with lower-intensity exercise, particularly after accounting for standard measurement uncertainty in clinical settings.
Why HIIT May Help Aging Muscles Stay Strong
One possible explanation for HIIT’s distinct advantage lies in the unique way it challenges the physiological systems of the body.
Rather than exercising at a steady, unchanging pace throughout an entire workout, HIIT repeatedly pushes both the cardiovascular system and working skeletal muscles through brief periods of intense effort, which are then followed by periods of easier activity.
University of the Sunshine Coast Associate Professor of Physiology and study co-author Mia Schaumberg explained the mechanics of how the training worked in practice.
"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," she said.
"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 physiological explanation aligns closely with the established biological principle that muscles constantly adapt to the specific demands placed upon them. When exercise provides a sufficiently challenging and demanding stimulus, the body has a much stronger biological reason to maintain the complex tissues required to perform that specific activity.
Muscle preservation is especially vital during the aging process, which is naturally accompanied by a gradual, progressive decline in muscle mass and strength. In more advanced cases, this age-related loss can contribute directly to sarcopenia, a medical condition characterized by heavily reduced muscle strength and quantity that can severely interfere with mobility and personal independence.
Dr. Schaumberg pointed out that the original research could ultimately help people make far more informed decisions regarding exercise and healthy aging strategies.
When the university publicized the study findings, she also highlighted their immediate relevance to people setting personal 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," she said. The broader research initiative involved key collaborators from both the University of the Sunshine Coast’s Healthy Ageing Research Cluster and The University of Queensland.
More Recent Studies Reveal Additional Benefits of HIIT
Subsequent research has provided further insight into how high-intensity interval training affects older adults, though it also suggests that intense workouts are not necessarily superior in every single scenario.
One study investigated whether older adults could safely benefit from completing HIIT at home with remote supervision. That study involved 20 older adults aged 61 to 74 who exercised using a specialized stationary machine that allowed them to work both their upper and lower limbs without bearing their full body weight.
After completing eight weeks of this targeted training protocol, the participants had lost an average of approximately 1.4 kilograms, or about 3 pounds, of body fat mass, while their overall aerobic fitness improved substantially.
Participants completed 96 percent of their scheduled workouts, and the researchers reported zero exercise-related adverse medical events during the trial. Although the sample size was relatively small, the findings suggested that appropriately supervised HIIT programs can successfully offer meaningful health benefits outside the confines of a conventional gym environment.
Another randomized trial compared HIIT with continuous moderate-intensity exercise specifically in older adults living with HIV. In that specific study, participants completed 16 weeks of structured exercise, with both experimental groups also performing standard resistance training alongside their aerobic intervals.
Unlike the original Australian study, both exercise groups in that trial experienced significant reductions in fat mass alongside notable increases in lean mass. The researchers found no statistically significant difference between the two distinct groups in terms of those specific body composition changes.
These results suggest that workout intensity may not be the only factor that matters for aging populations. Resistance training, which challenges muscles directly through weights or other external forms of resistance, may also play a powerful role in helping to preserve or increase lean tissue.
Because the studied populations and training programs differed across these investigations, experts note that 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 offers additional perspective on the topic by examining multiple reports and thousands of participants to assess how HIIT and other forms of interval training affect older adults.
The most consistent benefits identified across the scientific literature involved improvements in cardiovascular fitness, including enhanced capacity for the body’s ability to utilize oxygen efficiently during physical exertion.
Some studies reviewed also reported positive improvements in physical function and overall metabolic health. However, the comprehensive review did not establish that HIIT was consistently or universally superior to moderate-intensity exercise across the board.
The researchers involved in the review noted that variations between individual exercise programs, participant health characteristics, and scientific study methods made it difficult to pinpoint a single optimal training approach for every older adult.
Taken together, the collective body of scientific findings suggests that while HIIT can serve as a remarkably useful tool for healthy aging, it is certainly not the only valid pathway to improving overall fitness or protecting muscle tissue.
For adults over the age of 65, public health guidelines from organizations like the Centers for Disease Control and Prevention generally recommend a balanced combination of aerobic exercise, muscle-strengthening activities, and specialized exercises designed to improve stability and balance.
Higher-intensity workouts may indeed be appropriate for some older adults, but individuals who are currently inactive or managing underlying medical conditions are typically advised to gradually build up their baseline fitness levels and seek professional medical guidance before embarking on a demanding new exercise regimen.
Nevertheless, the central message delivered by the Australian research team remains compelling: what happens to vital muscle tissue during fat loss may ultimately be just as important as the simple amount of weight a person manages to lose.
HIIT showed distinct promise because it actively helped participants reduce their body fat while safeguarding lean tissue. Combined with newer insights from the scientific community, the research reinforces the true value of structured exercise programs that support not just a lower number on the bathroom scale, but the strength, fitness, and physical function necessary for sustained healthy aging.