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Where does the FAT go?

Updated: Jul 8, 2021

We’ve all seen the big transformations on TV where people lose half their body weight, dropping 40-50kg and 4 dress sizes. We continue to grow as an overweight nation. But have you every asked yourself; where does all that fat go?

There have been plenty of misconceptions and guesses as to where this fat disappears to, with the most common misconception being that the mass is predominantly converted into energy or heat. This misunderstanding is sometimes even common amongst health professionals, as recently stated by researchers from the University of New South Wales (2014).

The correct answer?

Most of the mass is breathed out as CARBON DIOXIDE. It literally disappears into thin air.

This evidence was recently confirmed in a research paper published by the British Medical Journal (2014), which ‘identified that losing 10 kilograms of fat required 29 kilograms of oxygen to be inhaled and that this metabolic process produces 28 kilograms of carbon dioxide and 11 kilograms of water’ (pg. 1). This water may be excreted as urine, sweat, breath or other bodily fluids.

150 allied health professionals were surveyed as part of the study, and over 50% of them thought the fat was converted to energy or heat.

So a seemingly obvious question from this recent research; If you increase your rate of breathing, will it increase weight loss? The answer is no.

If a person breaths faster than that of their metabolic rate, it can lead to hyperventilation, which can result in dizziness, palpitations and loss of consciousness.

So from an Exercise standpoint, what can we take from this?

Carbon dioxide and water are produced by metabolising the fat within the body.

It is the biochemical process of USING FAT FOR ENERGY that the body creates these excretions.

How can this change the way we think about weight loss and exercise?

Improved fitness = improved ability for your body to utilize fat

Different modes of exercise (e.g. resistance, cardiovascular) have different effects on the body and fat metabolism, and for the general population both work well in combination. However when first getting started, participation and finding activities you enjoy are the key.

Our Exercise Physiologists can help you lose weight safely and design programs and strategies to assist with co-morbities and motivation.

Please BOOK ONLINE NOW or call 6162 2616 (Canning Vale) or 6161 4091 (Hilton) to make an appointment today.


Meerman, R., Brown, A., 2014, ‘When somebody loses weight, where does the fat go?‘, British Medical Journal, 2014;349:g7257 doi: 10.1136/bmj.g7257

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