Does working out in the cold REALLY burn more fat?
For years we've been told that the more we sweat, the better. But what if the reverse were true?
AS we creep further and further towards winter, every day gets a bit darker and cooler.
If you struggled to work out in the summer, try drumming up the energy to get moving when it's pitch black at 7am and 7pm.
But if exercise folklore is to be believed, you might want to pull on your trainers and head outside for a wintery jog after all...because exercising in the cold is supposed to help you burn more calories.
Now that sounds odd, given that saunas and heated yoga studios are renowned for helping to shift the pounds. Surely heat means that you sweat more and thus burn more energy?
According to former NASA material scientist,, exercising in cool temperatures is the key to fat loss.
He claims that Michael Phelps, who is rumoured to put away 12,000 calories a day, is able to do so because he spends so much time in water.
It's not just that he's a top performing athlete who spends all day working out. A marathon only burns around 1,200 calories - so training for a swim sprint is likely to burn even less.
Usain Bolt, by contrast, is said to eat between 2,273 and 5,500 calories a day.
No, he needs so many calories because he's in water, and water is 24 times more thermally conductive than air.
"Maybe it was the water that was pulling the calories out through heat," Ray questioned in his .
As we get hot, our core temperature stays within a 2'C window.
Through a series of capillaries, our bodies send blood either to the surface to give off heat, or away from the skin to insulate itself.
Ray says that he used to believe that the way to lose weight was through sweaty hot workouts - but it turns out that when you're cold, you burn way more calories.
It all focuses around Newton's Law of Cooling, which says that heat will always move towards something cold.
He claims to have lost 30lbs in six weeks by going on "shiver walks", sleeping in the cold and taking cold showers - double the amount he was losing using diet and exercise alone.
So...how does it work?
Well, it's all down to something called "brown fat".
Heat-generating brown fat was only discovered in adults back in 2009 - before then, it was assumed to only be in babies (who don't shiver).
Scientists found that the colder the temperature, the more brown fat mice produced...and later, the same was discovered in human adults.
The more brown fat you have, the better insulin sensitivity you have (which means you're less likely to store belly fat)and the slimmer you tend to be.
How do can you increase your amount of brown fat?
Dr Pam Peeke is a "fat doctor" and she wrote on Maria's Farm Country Kitchen that exercise can convert white-yellow fat to brown fat, as can getting enough sleep and exposing yourself to cold temperatures regularly.
"Getting enough high-quality sleep (is important) as proper melatonin production influences the production of brown fat; and exposing yourself to the cold regularly, such as exercising outdoors in the wintertime or in a cold room. Lowering the temperature in your living and working spaces is another tip.
Darren Sealey is a PT and founder of boutique gym , and he told The Sun that working out in the cold really can burn more calories.
"It's due to something called thermogenesis," he explained.
"This is a metabolic process during which your body burns calories to produce heat.
"Several factors induce thermogenesis in your body including exercise, diet and environmental temperature which all need to be working harmoniously to increase the rate of thermogenesis in the body."
founder, Ben Claypole, broke it down even further: "Training in the cold and the heat will require your body to burn more energy as it is working very hard to bring your body temperature back to an equilibrium plus the energy being burnt during the exercise.
"This in turn as the result of more calories burn."
Does that mean you could also burn calories in a cold office?
Technically yes but the effect would be pretty minimal.
A study published in the journal Nature Medicine says that in order to increase your brown fat stores significantly, you've got to spend two hours a day in 18'C, dressed so that you're cold but not freezing.
Dutch scientists found that when people spent time in room where the temperature was reduced from 21'C to 15'C, they burned an extra 6 per cent.
And that means that if you typically burn around 2,000 kcals a day, you could burn up to an extra 120 kcals.
But that still won't help you stay slim once you get to a warmer environment - it's very much a short term solution.
It's worth saying that a rapid reduction in temperature has been found to increase a person's risk of stroke by 11 per cent so no one is suggesting you go and work out in the snow here.
So, should you work out outside during the winter rather than inside?
It's not going to make that much difference either way.
Cold can only do so much; think of it as the cherry on an already healthy, active cake.
As we revealed last month, you can't out-train a bad diet - whatever the temperature.
But certainly don't think that you should stop exercising outside just because it's gotten a bit nippy.
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Being outside will help you fight Seasonal Affective Disorder, as well as encouraging your body to produce more hard-to-find vitamin D.
The cold can also help to strengthen your lungs and circulatory system - to say nothing of making you feel more energised.
Just make sure that you take proper precautions. Wear layers if you need to, insulate your fingers and toes properly and be super careful of any icy patches.
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