There are a number of "fitness trends" out there that don't mean a thing. From people putting butter on their bodies to drinking special tea -- people will do just about anything to lose weight. But new research found that one thing we already do can truly help lose weight: a hot bath.
Many cultures swear by the benefits of a hot bath it makes us relaxed, gets us in the mood (wink, wink). But only recently has science began to understand how passive heating (as opposed to hot and sweaty exercise) improves your health.
Loughborough University investigated the effect of a hot bath on blood sugar control (which is super important in fitness) and the number of calories burned. Participants were assigned to an hour-long soak in a hot bath (40 degrees Celsius) or an hour of cycling. The activities were designed to cause a 1 degrees Celsius rise in core body temperature over the course of one hour.
Cycling resulted in more calories being burned compared with a hot bath, but bathing resulted in about as many calories being burned as a half-hour walk (around 140 calories). The overall blood sugar response to both conditions was similar, but peak blood sugar after eating was about 10 percent lower when participants took a hot bath compared with when they exercised.
In fact, the bathers' peak blood sugar levels after eating were about 10% lower than the peak blood sugar for the cyclists, which shows promise for using "passive heating" as a means of helping control metabolic disorders like type 2 diabetes.
The bathers also experienced an anti-inflammatory response similar to the effect seen in people after they exercise, which is also promising, since people with chronic disease tend to have chronic inflammation.
Passive heating for human health is a relatively new field of research, but some exciting results have emerged over the past few years.
In order to establish the effect of increasing body temperature passively, as opposed to through exertion, another study matched the intensity of heating from water immersion to that of running on a treadmill. Water immersion resulted in a greater increase in body temperature compared with exercise, as well as a greater reduction in average arterial blood pressure. This is important as a reduction in blood pressure is closely associated with a reduced risk of developing heart disease. This study points to the promising effect that may result from passive heating. It also suggests some of the cardiovascular effects of passive heating may be comparable with those of exercise.
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As well as the cardiovascular effects of passive heating, there is evidence to suggest that there may be beneficial metabolic effects as well – such as better control of blood sugar. The first study, conducted by Philip Hooper of McKee Medical Center, Colorado, in 1999, investigated the effect of three weeks of hot-tub therapy in patients diagnosed with type 2 diabetes. The results showed improvements in body weight, blood sugar control and a reduced dependence on insulin.
Hooper thought these effects may result from changes to blood flow as a result of passive heating, but he was unable to identify a specific mechanism by which their intervention led to these benefits.
It seems that activities that increase heat shock proteins may help to improve blood sugar control and offer an alternative to exercise. These activities—such as soaking in a hot tub or taking a sauna—may have health benefits for people who are unable to exercise regularly. Hopefully our future investigations, coupled with those of other groups worldwide, will help to establish the true potential of passive heating as a therapeutic tool.
