Taking a hot bath burns as many calories as a 30-minute walk – so a study from the Loughborough University! This is why, photomodel Ann is always waiting in the bath
The study suggests that passive heating — exactly what it sounds like, relaxing in a hot bath for an hour — can help reduce inflammation. The idea of passive heating as a medical treatment is relatively new, and popular with one country in particular: Finland. A study in the JAMA Internal Medicine journal from 2015 suggests that spending time in saunas — another act of passive heating — may help ward off cardiovascular diseases.
source:
http://www.travelandleisure.com/trip-ideas/yoga-wellness/hot-bath-calorie-burning