Ever wondered where does the fat in your body actually go when you lose weight?
The most common misconception among doctors, dieticians and personal trainers is that the missing mass gets converted into energy or heat.
“The correct answer is that most of the mass is breathed out as carbon dioxide. It goes into thin air,” says the study’s lead author Ruben Meerman, a physicist who has published the study in the British Medical Journal.
“There is surprising ignorance and confusion about the metabolic process of weight loss,” says Professor Andrew Brown, head of the UNSW School of Biotechnology and Biomolecular Sciences.
In their paper, the authors show that losing 10 kilograms of fat requires 29 kilograms of oxygen to be inhaled and that this metabolic process produces 28 kilograms of carbon dioxide and 11 kilograms of water.
Meerman became interested in the biochemistry of weight loss through personal experience.
“I lost 15 kilograms in 2013 and simply wanted to know where those kilograms were going.
With a worldwide obesity crisis occurring, we should all know the answer to the simple question of where the fat goes. The fact that almost nobody could answer it took me by surprise”.
Scientists estimate that an average person loses at least 200 grams of carbon every day and roughly a third of that occurs as we sleep.
Replacing one hour of rest with moderate intensity exercise, such as jogging, removes an additional 40 grams of carbon from the body, raising the total by about a fifth to 240 grams.
“Losing weight requires unlocking the carbon stored in fat cells, thus reinforcing that often-heard refrain of eat less, move more,” say the researchers.
One of the most frequently asked questions the authors have encountered is whether simply breathing more can cause weight loss.
The answer is no.
Breathing more than required by a person’s metabolic rate leads to hyperventilation, which can result in dizziness, palpitations and loss of consciousness.
When fat is broken down to its constituent parts, chemical bonds are broken, a process which releases heat and fuel to power muscles.
But the atoms remain, and much of these leave the body via the lungs as carbon dioxide, say the scientists.