While performing hot yoga isn't harmful if done properly, it does not make the body work harder than any other type of yoga.
Dr Cedric Bryant, chief science officer of the American Council on Exercise (ACE) said the benefits are largely perceptual.
"People think the degree of sweat is the quality of the workout, but that's not reality," he said.
"It doesn't correlate to more calories."
ACE sponsored a small study at the University of Wisconsin-La Crosse, in which researchers who monitored two dozen healthy adults during regular and hot yoga classes found no difference in the increase in core temperature or heart rate between the two 60-minute sessions.
Dr Bryant said that people enjoyed hot yoga because it allowed them to feel more flexible.
But as far as physical benefits, including muscular strength, endurance, flexibility and balance, you can get those from a standard yoga class, he said.
"An increase in core temperature would suggest the person is storing heat, and depending on how high, would be at risk for heat injury.
"We didn't find that."
For the study, the hot yoga was conducted in an average temperature of 33 degrees. Bryant said in classes, including the popular Bikram style, where the temperature rises to 40.5 or higher, further study is needed.
"Many folks want to know what happens in that really extreme class," he said.
"Our study says you don't have to be at those extreme temperatures to get all those benefits."
Hot yoga is becoming increasingly popular and is been practised by celebrities including Gwyneth Paltrow, Madonna and Wimbledon winner Andy Murray.
Its fans believe that exercising at such high temperatures forces the body to work harder, and the sight of the sweat dripping off them encourages the belief they are burning the flab.
London yoga teacher and personal trainer Claire Finlay, who runs the Transition Zone studio in south-west London, agrees with the findings of the study.
"To burn calories, your body requires oxygen. The harder the exercise, the more oxygen you require and the harder you breathe," she said.
"Your heart may need to work a little harder to keep your muscles oxygenated (and to cool the body down) in a Bikram class, but this would be no different than in many other yoga classes particularly a dynamic Power yoga session, which can be quite cardio-driven and very hot and sweaty.
"Evidence on the scales after a Bikram yoga class can be mistaken for fat burn rather than fluid loss, but the sweating alone does not burn fat.
"If it did, we could all sit in the sauna and melt away the fat."
What is Bikram yoga?
Devised by and named after 67-year-old Bikram Choudhury, Bikram yoga is based on regular hatha yoga, but performed in sweltering temperatures and with a high (40 per cent) degree of humidity.
Its fans claim that not only does it leave them stronger and more flexible than standard yoga, it also helps them shed weight fast.
Choudhury began practising yoga in Calcutta at the age of four, spending up to six hours a day perfecting his poses.
At 13 he won the National India Yoga Championship and went on to devise the 26 'asanas' (poses) and two breathing methods that form the core of Bikram yoga.
In 1973 President Nixon invited Choudhury to the US to help him improve his health, and soon Nixon was the darling of American celebrities, with clients including Michael Jackson and Madonna.
Bikram copyrighted his 26 poses and franchised his exercise methods, and the craze spread from America's West Coast to the UK in 2000, when Brit Michele Pernetta set up the country's first Bikram studio in north London.
Choudhury says Bikram works because the 40C heat loosens the muscles, helping them to go further than they would otherwise.
Yogis perform the series of poses, pushing their bodies to the limit, and are encouraged to drink vast quantities of water to replace that lost by sweat.
Teachers say that if it gets too much for they, they should lie on the floor or leave the room for lower temperatures.
Students, who carry a towel to mop up their sweat, are taught to watch out for danger signs including nausea, lightheadedness and dizziness.
- DAILY MAIL