One Type of Workout Helped Adults in Their 70s Lose Fat Without Losing Muscle

Here is a rare piece of good news about getting older: you do not have to trade away your muscle to lose body fat. A six-month study of more than 120 healthy adults in their 70s found that every exercise intensity tested trimmed a modest amount of fat - but only one of them, high-intensity interval training, let people keep all of their hard-won muscle. In an age of complicated wellness advice, the takeaway is refreshingly clear: as we age, how hard we train, not just how often, may be what protects the muscle that keeps us strong, steady, and independent.

Here is what the researchers did, what they found, why keeping muscle matters so much after 60, and how to put it to work safely.

At a glance

Who: 120+ healthy older adults (Greater Brisbane), average age 72, average BMI 26 (normal for over-65s)
What: 6 months of supervised, gym-based training, 3 sessions a week, across three intensities - HIIT, moderate, and low
Result: all three trimmed a modest amount of body fat; only the HIIT group preserved lean muscle
Bonus: HIIT produced the biggest drop in overall body-fat percentage; both HIIT and moderate improved the fat carried around the middle
Likely why: harder efforts put more stress on muscle, signaling the body to keep it
Published in: Maturitas (DOI 10.1016/j.maturitas.2025.108763), University of the Sunshine Coast

1. The Experiment

Exercise physiologist Dr. Grace Rose and colleagues at the University of the Sunshine Coast, working with the University of Queensland, recruited a group of healthy older adults - more than 120 people, average age 72, with an average body-mass index of about 26, which is considered normal for adults over 65. Everyone trained three times a week in a supervised gym setting for six months. The one thing that differed between groups was intensity:

High-intensity interval training (HIIT) - repeated short bursts of very hard effort, the kind where your breathing is heavy and holding a conversation is difficult, alternated with easier recovery periods.
Moderate-intensity training - continuous, steady effort you could sustain and still chat through.
Low-intensity training - gentle, easy sessions designed above all to be comfortable and sustainable.

At the start and end, the team measured body composition - not just weight on a scale, but how much of the body was fat versus lean muscle. That distinction is the whole point, because the number on the scale hides the trade that matters most as we age.

2. What They Found

All three intensities did something good: every group lost a modest amount of body fat over the six months. The difference showed up in the muscle.

Group	Body fat	Lean muscle
HIIT	Modest loss - biggest drop in overall body-fat percentage	Preserved
Moderate	Modest loss; improved fat around the middle	Small decline
Low	Modest loss	Needs further analysis

In the researchers' plain summary, as Dr. Rose put it: “We found that high, medium and low intensity exercises all led to modest fat loss but only HIIT retained lean muscle.” The moderate group is the instructive one: it lost fat and improved the fat carried around the waist, yet still slipped backward on muscle. HIIT was the only approach that delivered the loss without the cost - and it cut the most overall body fat besides.

3. Why Keeping Muscle Is the Whole Game After 60

From roughly our 50s onward, most people slowly lose skeletal muscle - a process called sarcopenia. It is easy to shrug off, because it is invisible on a bathroom scale, but muscle is doing an enormous amount of quiet work:

Strength and independence - carrying groceries, standing up from a chair, climbing stairs.
Balance and stability - strong legs and hips are among the best defenses against falls, one of the biggest threats to healthy later life.
Metabolic health - muscle is metabolically active tissue that helps manage blood sugar; changes in fat and muscle are linked to heart disease and type 2 diabetes.

The trade that matters

Plenty of ways to “lose weight” also quietly cost you muscle - and for an older adult, shedding fat while shedding muscle can be a net loss. The goal is recomposition: fat down, muscle held steady (or built). This study is a hint that intensity is one of the levers that tilts the outcome the right way.

4. Why Intensity Seems to Protect Muscle

The researchers' proposed explanation is intuitive. As they described it, HIIT “puts more stress on the muscles, giving the body a stronger signal to keep muscle tissue rather than lose it.” A hard interval demands a lot from your muscle fibers in a short window; that mechanical and metabolic stress is a message to the body that this tissue is needed and worth maintaining. Gentler, steady effort burns energy but sends a weaker “keep me” signal.

This fits well with established exercise science. Higher-effort work preferentially recruits the larger, fast-twitch muscle fibers that tend to be lost first with age, and it drives the anabolic (build-and-maintain) signaling that helps preserve muscle protein. It is the same reason resistance training is so protective for older adults - and a reminder that vigorous cardio, done in intervals, can carry some of that muscle-sparing benefit too.

5. What HIIT Actually Looks Like (and How to Start Safely)

“High intensity” does not mean sprinting flat-out or doing anything punishing. It means brief periods of genuinely hard effort - breathing heavy, conversation difficult - separated by easier recovery. Crucially, it is scalable to almost any starting point:

Pick a mode that is kind to your joints: a stationary bike, the pool, a rowing machine, or an incline walk all work. (The study was gym-based and supervised.)
Keep intervals short: something like 30-60 seconds of hard effort followed by 1-2 minutes easy, repeated a handful of times, is plenty to start.
Build gradually: begin with fewer, shorter intervals and add over weeks as you adapt.
Get clearance first: if you have heart, blood-pressure, or joint concerns - or you are new to vigorous exercise - check with your doctor before ramping up intensity. Supervision, at least early on, is wise.

The Honest Caveats

Healthy volunteers. Participants were healthy older adults with a normal average BMI. The results may not transfer to people with obesity, chronic conditions, or significant mobility limits - the groups most in need of tailored guidance.
Modest, not miraculous. The fat losses were described as modest. Exercise is a powerful lever, but it complements rather than replaces sleep, nutrition, and overall activity.
A comparison over six months. This was a six-month comparison of three training intensities, and the public summaries report the direction of the changes rather than a full table of percentages; the low-intensity results in particular, the team notes, need further analysis.
One study, consistent with the bigger picture. It does not overturn the cornerstone advice that resistance training builds and protects muscle - it adds to it, suggesting interval-style cardio can be muscle-sparing too.

Even with those limits, the message is empowering and rare in its optimism: the body in your 70s still responds - and a little well-judged intensity may be exactly what keeps your muscle where it belongs.

Sources

Curated by Jerry Cards - jerrycards.com. We research the week's most useful tech, science, and health news so you don't have to. More at jerrycards.com/news.