HIIT Preserves Muscle While Reducing Fat in Older Adults, Study Finds

Can Exercise Intensity Influence Healthy Ageing?

Maintaining a healthy body composition becomes increasingly important with age. Excess body fat, particularly visceral fat surrounding internal organs, is linked to chronic diseases such as cardiovascular disease, type 2 diabetes, and functional decline. At the same time, preserving lean muscle mass is essential for maintaining mobility, independence, and metabolic health.

Researchers from Australia recently investigated whether exercise intensity could influence these outcomes in healthy older adults. Their findings suggest that not all exercise intensities produce the same effects on body composition.  

How the Study Was Conducted

The study included 123 healthy adults with an average age of 72 years and an average BMI of 25.8 kg/m². Participants were randomly assigned to one of three exercise groups:

• High-Intensity Interval Training (HIIT)
• Moderate-Intensity Continuous Training (MICT)
• Low-Intensity Training (control group)

All participants completed three supervised exercise sessions per week for six months. Researchers assessed body composition using dual-energy X-ray absorptiometry (DEXA) scans at baseline, three months, and six months. Measurements included fat mass, fat-free mass (lean mass), body fat percentage, and visceral adipose tissue.

HIIT Delivered the Most Favourable Results

The researchers found that both HIIT and moderate-intensity training reduced overall fat mass compared with the low-intensity control group.

However, important differences emerged when lean mass was examined.

Participants in the moderate-intensity group experienced reductions in fat-free mass over the course of the intervention. In contrast, individuals performing HIIT maintained their lean tissue while simultaneously reducing body fat.

HIIT was also the only intervention associated with a net improvement in body fat percentage after six months.  

Both HIIT and Moderate Exercise Reduced Visceral Fat

Visceral adipose tissue is considered one of the most harmful forms of fat because of its strong association with metabolic disease and inflammation.

The study found that both HIIT and moderate-intensity training significantly improved visceral fat levels compared with baseline measurements. The improvements were similar between the two exercise groups, indicating that both training approaches can support metabolic health in older adults.

Were the Changes Clinically Meaningful?

Although HIIT demonstrated superior body composition outcomes, the researchers emphasised that the magnitude of the changes was relatively small.

The improvements did not reach thresholds generally considered clinically meaningful for most participants. Nevertheless, preserving muscle mass while reducing fat remains an important objective in ageing populations, and the findings suggest that higher-intensity aerobic exercise may offer a modest advantage.

What Do These Findings Mean?

The study adds to growing evidence that exercise intensity matters, especially in older adults. While moderate-intensity exercise remains highly beneficial for overall health, HIIT may provide additional advantages for preserving muscle tissue while reducing body fat.

The authors also noted that combining HIIT with resistance training could potentially generate even greater benefits by supporting muscle maintenance and growth alongside fat reduction. Future research will be needed to determine the optimal exercise prescription for healthy ageing.  

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Why This Matters for GeneFit Readers

Healthy ageing is not simply about losing weight. Preserving lean muscle mass while reducing harmful body fat is one of the most important goals for long-term health, mobility, and disease prevention.

At GeneFit, we recognise that responses to exercise can vary substantially between individuals due to genetics, age, metabolism, and lifestyle factors. This study highlights the importance of personalised exercise strategies rather than one-size-fits-all recommendations.

By integrating genetic insights with fitness and metabolic assessments, GeneFit helps individuals identify exercise approaches that may be most effective for optimising body composition, maintaining muscle health, and supporting longevity.

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Reference

Rose, G., Hume, E., Blackmore, D., Mitchell, J., Belford, S., Skinner, T., Ziaei, M., Riek, S., Bartlett, P., & Schaumberg, M. (2025). Exercise intensity influences body composition: A 6-month comparison of high-intensity interval, moderate- and low-intensity training among healthy older adults. Maturitas, 203, 108763. https://doi.org/10.1016/j.maturitas.2025.108763

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