Hot water baths can help improve chronic inflammation and blood sugar levels in overweight people who are not able to exercise. The results of the study were published in the Journal of Applied Physiology.
Physical stress, such as exercise, can cause short-term increases in inflammatory markers. After exercise, for example, the level of interleukin 6 (IL-6) increases, followed by the release of other cytokines. This inflammatory response fights the onset of low-grade chronic systemic inflammation, a pathological condition. Recent research has shown that rising body temperature increases the inflammatory response. Previous studies have also found a connection between a peak body temperature and the production of nitric oxide, a powerful vasodilator that promotes blood flow and facilitates the collection of glucose in the tissues.
Researchers studied markers of inflammation and blood sugar and insulin levels in a group of overweight sedentary men (BMI: 31.0±4.2 kg/m2). Volunteers took part in tests of immersion in hot water and at room temperature (control) separated by at least three days. During the hot water test, the volunteers sat up to their necks in water at 39 °C for 60 minutes. The research team measured the heart rate, blood pressure and body temperature of the men every 15 minutes, both under controlled and diving conditions. The blood samples were taken again two hours after each session.
Researchers found that a single session of immersion in hot water resulted in increased levels of IL-6 in the blood and increased production of nitric oxide, but did not change the expression of the protein by thermal shock 72 (HSP72), suggested as important for health. A two-week treatment period in which men participated in daily hot water baths showed a reduction in fasting glycemia and insulin levels, as well as an improvement in low-grade chronic systemic inflammation.
Subjects reported a high level of discomfort during the hot water immersion test. Researchers acknowledge that this may limit the spread of this treatment. However, the results suggest that immersion in hot water may improve aspects of the inflammatory profile and improve glucose metabolism in sedentary and overweight males and may have implications for improving metabolic health in populations that are unable to meet current recommendations to perform physical activity.
Hoekstra SP, Bishop NC, Faulkner SH, Bailey SJ, Leicht CA. The acute and chronic effects of hot water immersion on inflammation and metabolism in sedentary, overweight adults. J Appl Physiol (1985). 2018 Oct 18.doi: 10.1152/japplphysiol.00407.2018.