Do you know what happens to body fat when you lose weight?

Many nutritionists, physicians, physical trainers and people who should know better think lost weight leaves our bodies as heat, gets converted into muscle or passed out in the feces. But it largely leaves the body in the form of carbon dioxide exhaled from our lungs, according to an article in the British Medical Journal.

Losing weigh requires unlocking the carbon stored in fat cells, and lungs “are the primary excretory organ for fat,” wrote Ruben Meerman and Andrew J. Brown of Australia’s University of New South Wales.

Someone setting a goal of losing weight without losing lean muscle is, in effect, planning to metabolize the triglycerides stored in the adipocytes, or fat cells. Chemically speaking, triglycerides must be oxidized, or broken down into their component parts. Oxidizing 10 kilograms of fat will take 29 kilograms of inhaled oxygen, and will produce 28 kilograms of carbon dioxide and 11 kilograms of water.

The researchers estimate that an average person loses at least 200 grams of carbon every day, roughly a third of that as we sleep.

An additional 40 grams of carbon are removed from the body by replacing one hour of rest with moderate-intensity exercise, such as jogging.

Can simply breathing more cause weight loss? Of course it’s not that easy. You need to balance what you eat against what you burn off and exhale.

“Losing weight requires unlocking the carbon stored in fat cells, thus reinforcing that often heard refrain of ‘Eat less, move more,’ ” the authors wrote. They said the “widespread misconceptions” about weight loss show the biochemistry of the process ought to be taught in schools.

Los Angeles Times