High-intensity interval training (HIIT) is the most effective exercise method for reducing body fat while preserving muscle mass in older adults, according to a recent study published in the journal Maturitas. While both moderate-intensity and HIIT programs decrease body fat, researchers found that moderate-intensity exercise can lead to minor muscle loss, whereas HIIT maintains lean tissue.
How HIIT preserves muscle while burning fat
The study followed 123 healthy adults with an average age of 72. Researchers assigned participants to one of three groups: low-impact, moderate-intensity, or HIIT. After six months of supervised, 45-minute sessions three times a week, body composition scans showed that only the HIIT group successfully shed fat without sacrificing muscle.
Karena Wu, D.P.T., a board-certified clinical specialist in orthopedic physical therapy, explains that the interval structure is the primary driver of this result. “The extremely high-intensity exercises will recruit more muscle fibers to help with muscle mass maintenance,” Wu says. By incorporating active recovery periods, the body can optimize performance during the high-intensity bursts, which prevents the muscle atrophy sometimes seen with steady-state cardio.
Competitive bodybuilders often utilize HIIT during fat loss phases specifically because it helps them retain lean muscle mass while cutting body fat, according to Anna Di, D.C., C.E.S., a corrective exercise specialist and chiropractor.
Why muscle maintenance matters for aging
Retaining muscle mass is a priority for longevity, as it directly impacts strength, mobility, and balance. Di notes that muscle tissue also serves a vital role in blood sugar regulation. Furthermore, muscle acts as a mechanical stressor on the skeletal system.
“Muscles are what pull on our bones,” Di explains. “That mechanical stress is one of the signals that helps bones stay thicker and stronger over time.” This process is particularly critical for post-menopausal women and older adults at increased risk of osteoporosis.
Are there risks to high-intensity training?
While effective, HIIT is not universally appropriate. The high-impact nature of the workouts can increase the risk of injury for those with preexisting conditions. Wu advises that individuals with uncontrolled cardiovascular issues, significant joint problems, or poor core and pelvic strength should avoid this training style.
Additionally, HIIT can spike cortisol levels. Wu warns that people who struggle with high stress levels or poor stress management should avoid the regimen to prevent physiological strain.
Choosing the right exercise for your lifestyle
The best workout is ultimately the one you will perform consistently. While the Maturitas study highlighted the specific muscle-sparing benefits of HIIT, Di emphasizes that moderate-intensity and low-impact exercise remain excellent choices for many people.
Low-impact activities—such as the stretching and toning classes used in the study—provide benefits that HIIT may not, including improved flexibility and balance. “The biggest takeaway is that both high-intensity and moderate-intensity exercises worked,” Di says. “For someone who’s older, new to exercise, or simply doesn’t enjoy high-intensity workouts, a regular walking program may still be an excellent option if it’s something they’ll consistently do.”
Frequently Asked Questions
- Is HIIT safe for everyone over 70? No. Individuals with joint pain, cardiovascular conditions, or high stress levels should consult a physician before beginning a HIIT program.
- Does moderate-intensity exercise cause muscle loss? The study found that moderate-intensity programs resulted in a small amount of muscle decline compared to HIIT.
- How many times a week should I do HIIT? The study participants performed three 45-minute sessions per week.
- Can I do HIIT at home? Yes. While the study utilized treadmills, HIIT can include any whole-body exercise, such as bodyweight strength or resistance training, provided it follows an interval structure.
Have you incorporated interval training into your weekly routine, or do you prefer lower-impact movement? Share your experiences in the comments below or subscribe to our weekly newsletter for more evidence-based fitness tips.
