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By Maggie Fox

You can lose weight, just by breathing!

The headline seems too good to be true, but it’s scientific fact, as laid out in the British Medical Journal.

Every breath you let out take carries a little body fat in it.VIKTOR DRACHEV / Today

Ruben Meerman and Andrew Brown at the University of New South Wales in Australia calculated just how much. The good news is that each breath carries not just water weight, but actual matter, in the form of carbon atoms, taken right out of your fat cells.

The bad news is, it’s not very much.

Meerman and Brown ran the calculations and found that when 10 kg —22 pounds — of fat are fully broken down in a process called oxidation, 18.5 pounds of it leaves the body as exhaled carbon dioxide and the rest is breathed out as water vapor.

“Our calculations show that the lungs are the primary excretory organ for fat,” they wrote in their report, published in the notoriously lighthearted Christmas issue of the BMJ.

Most people just don’t understand this, they said.

“We encountered widespread misconceptions about how humans lose weight among general practitioners, dietitians, and personal trainers,” they wrote. “Most people believed that fat is converted to energy or heat, which violates the law of conservation of mass.”

In fact, fat breaks down into the elements of carbon, oxygen and hydrogen. Hydrogen is the lightest, and combines with oxygen to make water. The three elements make up the basic building blocks of living matter, including carbohydrates and fat.

This actually explains why exercise helps people lose weight. It speeds up breathing. The more breaths you take, the more carbon you lose. And you also lose a little weight just sitting on the couch watching TV, or even while you're asleep.

Unfortunately, general living easily compensates for this loss. And it doesn't alter the depressing fact that one pound of body weight equals 3,200 calories.

That muffin is about 20 percent of your total daily energy requirement. Still want it? Today

“For comparison, a single 100 gram muffin represents about 20 percent of an average person’s total daily energy requirement,” Meerman and Brown wrote.

“Physical activity as a weight loss strategy is, therefore, easily foiled by relatively small quantities of excess food.”

So the advice remains the same, whether you understand the scientific principles or not. “Losing weight requires unlocking the carbon stored in fat cells, thus reinforcing that often heard refrain of ‘eat less, move more’,” they concluded.