Losing body fat is one thing, but shedding unwanted pounds while keeping the muscle that helps you stay strong and active is another challenge entirely, especially as you get older. New 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 (HIIT), a workout strategy that 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 valuable lean muscle mass.
In a study published in the journal Maturitas, a team of researchers from the University of the Sunshine Coast compared three different exercise intensities to determine their specific impacts on aging bodies. Although participants across all the groups experienced modest overall fat loss, HIIT stood out for its unique ability to trim fat while successfully 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 a critically important distinction in the field of healthy aging: losing weight on a standard scale 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 workout intensity directly affects body composition, which refers to the precise 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 volunteered to participate in the comprehensive 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.
Over the course of the study, the participants completed three supervised gym sessions each week for six consecutive months. Each individual session lasted for a total of 45 minutes. Depending on their assigned group, participants performed high-intensity intervals, moderate-intensity continuous exercise, or a low-intensity comparison routine.
To track physical changes over time, researchers measured each participant’s body composition at the very beginning of the study, at the three-month mark, and again at the conclusion of the six-month trial. They utilized a specialized, advanced scanning technique designed to accurately estimate fat and lean tissue distribution throughout the entire body.
The final findings revealed that exercise intensity made a significant difference in the physiological outcomes. Both high- and moderate-intensity training significantly reduced overall fat mass, yielding larger improvements than those observed in the low-intensity group. However, the two more demanding workout approaches differed noticeably 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 the high-intensity intervals, meanwhile, successfully reduced their fat mass without experiencing that same measurable decline in lean mass.
This preservation of lean tissue could prove particularly valuable later in life, when maintaining muscle becomes increasingly crucial for sustaining physical independence. Strong muscles help older individuals climb stairs safely, rise easily out of chairs, maintain reliable balance, and carry out everyday domestic and social activities without outside assistance.
Researchers noted one important methodological distinction: the specialized scans measured overall lean tissue rather than direct muscle strength. Lean mass includes muscle tissue along with water and other bodily components, meaning that changes in these specific measurements do not necessarily translate into equivalent, direct changes in physical strength.
High-Intensity Exercise Also Reduced Abdominal Fat
Beyond overall body composition, the researchers uncovered another potentially vital benefit involving the dangerous accumulation of fat stored deeply 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," Dr. Rose explained.
The original study documented clear improvements in visceral adipose tissue among both the high- and moderate-intensity workout groups. Visceral fat is fundamentally different from the subcutaneous fat that sits directly beneath the skin. Instead, it accumulates much deeper within the abdominal cavity, surrounding internal organs such as the liver, pancreas, and intestines.
Excessive amounts of this visceral fat have long been linked by medical professionals to insulin resistance, cardiovascular disease, and a wide array of other serious metabolic problems. According to Dr. Rose, these specific findings matter deeply because body composition can directly influence the development and progression of chronic diseases as people grow older.
While standard body weight and body mass index measurements provide useful general information for clinical settings, they fail to reveal how much actual fat or muscle a person carries, or precisely where that excess fat is being stored inside the body.
Consequently, an individual who loses fat while successfully maintaining muscle mass may experience a vastly more favorable change in body composition than someone who loses a similar amount of overall weight while simultaneously sacrificing valuable lean tissue.
Still, the original researchers emphasized that the observed improvements were relatively small in magnitude. They cautioned that the differences were not entirely clear-cut in terms of direct clinical meaning when compared against lower-intensity exercise, particularly after properly accounting for standard measurement uncertainty.
Why HIIT May Help Aging Muscles Stay Strong
One possible scientific 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 the duration of a workout, HIIT repeatedly pushes the cardiovascular system and working muscles through demanding periods of intense effort, followed immediately by periods of easier recovery activity.
University of the Sunshine Coast Associate Professor of Physiology and study co-author Mia Schaumberg explained the mechanics of the training protocol.
"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," Dr. Schaumberg 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 is entirely consistent with the broader biological principle that muscles actively adapt to the specific demands placed upon them. When a workout provides a sufficiently challenging stimulus, the body is given a much stronger biological reason to maintain the heavy tissues required to perform that exact activity.
Muscle preservation is especially vital for older populations because the natural aging process is frequently accompanied by a gradual, progressive decline in both muscle mass and overall strength. In more advanced cases, this degenerative process can contribute significantly to sarcopenia, a debilitating medical condition characterized by heavily reduced muscle strength and quantity that can severely interfere with personal mobility and independence.
Dr. Schaumberg pointed out that the original research could ultimately help aging individuals make far more informed, evidence-based decisions regarding their personal exercise habits and long-term health strategies. When the university publicized these findings, she highlighted their clear relevance for people establishing new 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 at the time. The foundational research project involved close collaborators from UniSC’s Healthy Ageing Research Cluster as well as researchers from The University of Queensland.
More Recent Studies Reveal Additional Benefits of HIIT
Subsequent research has provided further critical insight into how high-intensity interval training affects older adults, though these modern investigations also suggest that intense workouts are not universally superior in every single fitness scenario.
One study investigated whether older adults could safely and effectively benefit from completing HIIT routines at home utilizing remote professional supervision. That project involved 20 older adults aged 61 to 74 who exercised regularly using a specialized piece of equipment designed to let them work both their upper and lower extremities without bearing their full body weight.
After eight weeks of consistent home-based training, those participants had lost an average of approximately 1.4 kilograms of fat mass. Furthermore, their overall aerobic fitness levels improved substantially. Participants successfully completed 96 percent of their scheduled workouts, and the study authors reported zero exercise-related adverse medical events throughout the trial. Although that particular trial was relatively small in scale, its findings strongly suggest that appropriately supervised HIIT programs can deliver meaningful physiological benefits outside the confines of a traditional gymnasium.
Another randomized clinical trial compared high-intensity interval training directly with continuous moderate-intensity exercise in a cohort of older adults living with HIV. In that specific protocol, participants completed 16 weeks of structured exercise, with both groups also incorporating standard resistance training into their routines.
Unlike the original Australian study, both exercise groups in that trial experienced notable reductions in body fat alongside distinct increases in lean mass. The investigators found no statistically significant difference between the two active groups regarding those specific body composition shifts.
These results strongly suggest that workout intensity is not the sole factor that matters for aging populations. Resistance training, which challenges muscle fibers directly through external weights or other forms of physical opposition, may play an equally powerful role in helping to preserve or increase lean tissue over time. Because the studied populations and training programs differed across these trials, experts stress that the newer findings should not be interpreted as a direct contradiction of the earlier Australian results.
Is HIIT Really the Best Exercise for Older Adults?
A broader scientific review published in the Journal of Clinical Medicine offers additional, comprehensive perspective on the matter. Researchers analyzed 25 separate reports involving approximately 2,818 total participants to evaluate how HIIT and other forms of interval training impact older adults across diverse settings.
The most consistent benefits identified in the review involved cardiovascular fitness, particularly improvements in the body’s physiological capacity to utilize oxygen efficiently during physical exertion. Some of the reviewed studies also reported measurable improvements in general physical function and key markers of metabolic health. However, the comprehensive review ultimately could not establish that HIIT was consistently superior to traditional moderate-intensity exercise across the board.
The review authors noted that substantial differences between individual exercise programs, participant health characteristics, and overarching study methodologies made it remarkably difficult to isolate and identify a single, universally optimal training approach for every older adult.
Taken together, the scientific literature suggests that while HIIT can serve as an exceptionally useful tool for supporting healthy aging, it is certainly not the only valid pathway to improving overall fitness or protecting aging muscles.
For adults over the age of 65, public health authorities such as the Centers for Disease Control and Prevention recommend a well-rounded combination of aerobic exercise, dedicated muscle-strengthening activities, and specialized movements designed to improve balance. While higher-intensity workouts may be entirely appropriate for some active older individuals, people who are currently sedentary or managing complex medical conditions can benefit greatly from gradually building up their baseline fitness and seeking professional medical guidance before launching into a demanding new program.
Ultimately, the central message delivered by the Australian research team remains compelling: what happens to vital muscle tissue during fat loss may be just as important to overall health as the sheer amount of weight a person manages to lose.
High-intensity interval training has shown distinct promise because it actively helps participants reduce harmful body fat while simultaneously defending precious lean tissue. Combined with newer insights from ongoing clinical research, these findings reinforce the profound value of exercise programs that support not just a lower number on a bathroom scale, but the foundational strength, fitness, and physical function required for sustained, healthy aging.