The only workout to lose fat and keep muscle: high-intensity.

So much for my tai chi. After a six-montd, y stuyScience Daily says, especially with older adults, only one kind of exercise reliably loses fat while keeping muscle, and that’s a hard workout with built-in breaks:

High-intensity interval training (HIIT), which 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 lean muscle.

In a study published in Maturitas, researchers from the University of the Sunshine Coast compared three different exercise intensities. Although participants across the groups experienced modest fat loss, HIIT stood out for its ability to reduce fat while 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.

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One possible explanation for HIIT’s advantage lies in the way it challenges the body.

Rather than exercising at the same pace throughout a workout, HIIT repeatedly pushes the cardiovascular system and working muscles through periods of intense effort, followed by easier activity.

University of the Sunshine Coast Associate Professor of Physiology and study co-author Mia Schaumberg explained how the training worked.

“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.

“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.”

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You can read more about the six-month study here, in Maturitas.