Unusual daily activity 'could help burn abdominal fat and reduce disease risk', new study finds

A daily sauna could help prevent middle-aged women from piling on the pounds, according to new research. The study conducted with mice suggests that daily time in a warm environment - such as a sauna - might help older people, especially women, combat age-related obesity and insulin resistance.

The findings show the potential of heat treatments as a simple way to promote healthier ageing, say scientists. The American research team found that older female mice receiving a daily 30-minute whole-body heat treatment gained less weight and showed improved use of insulin, which helps control blood sugar. They also identified the biological processes responsible for the beneficial effects.

Research team leader Professor Soonkyu Chung, of the University of Massachusetts, Amherst, said: “Compared to men, women have a higher likelihood of being obese or overweight. This is especially true after menopause, due to the loss of oestrogen in the body. Our study suggests that whole-body heat therapy could serve as an effective, non-invasive solution for managing weight gain and insulin resistance associated with menopause.”

Rong Fan, a doctoral candidate advised by Prof Chung, said: “Heat therapy could be a practical option for those with increased abdominal fat and a higher risk of metabolic diseases triggered by menopausal hormonal changes. It could be easily integrated into routine healthcare practices through regular sessions in saunas, heated baths or with specialised heat wraps.”

The ovaries of older female mice were removed to model post-menopausal conditions for the study. To induce weight gain, the mice received a Western diet that contained 45% calories from fat.

One group of mice received 30 minutes of daily heat therapy in a heat chamber set to 40 degrees Celcius (104F) for 12 weeks while the other group didn't receive any heat treatment. The mice receiving the heat treatment showed no tissue damage and showed "significantly" reduced lactate dehydrogenase levels, indicating less ageing-related tissue damage.

The therapy also effectively mitigated weight gain induced by a high-fat diet. Compared to the mice not receiving the treatment, those that underwent heat therapy showed "significant" improvements in insulin sensitivity and insulin signalling as well as reduced fat accumulation in key areas such as the liver and in brown fat.

The team explained that while adipose tissue stores energy, brown fat is a metabolically active type of fat that helps the body burn more energy. Previous studies have shown that people tend to lose brown fat as they age and when entering menopause, which contributes to a slower metabolism.

The research team also looked at the molecular mechanisms involved in the beneficial effects of heat therapy. They found that the heat triggers several molecular processes that help the body use energy more efficiently and burn fat.

A key player is a protein known as TRPV1, which functions as a calcium ion channel in the cell membrane. When activated by heat, TRPV1 kicks off a process known as "futile calcium cycling" where the body uses up energy - in the form of ATP - to pump calcium ions across cell membranes. The process helps increase the amount of energy the body burns, say scientists.

TRPV1 activation and the subsequent calcium cycling also stimulate the breakdown and burning of fats, reducing fat accumulation in tissues such as the liver and helping improve the body's insulin sensitivity, which is crucial for overall metabolic health.

Ms Fan said: “This series of events suggests that regular application of heat can mimic the effects of calorie burning and fat loss."

She added: “It could be particularly advantageous for individuals who find physical activities challenging, providing a relaxing way to improve metabolic health.”

The team says that more research needs to be done to determine the optimal duration and intensity of heat exposure in people for health benefits. The findings were presented at the annual meeting of the American Society for Nutrition in Chicago.