Where does the weight go when we lose weight?

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weight-loss-1

 

Weight loss is a billion dollar industry, and we all know that eating more healthily and being more active is the best way to weight loss (despite all those quick fixes, miracle cures and late night infomercials). But when you lose weight, where does the weight actually go???

It’s something that sounds like it should be a simple question to answer. But when we discussed it at the clinic, and with other clients and health professionals, most admitted that they actually didn’t know. What do you think? These were the most common answers we could come up with:

  • It gets transferred into heat/energy
  • You lose it through sweat
  • It goes into your urine (or faeces) and is excreted that way
  • It turns into muscle/bone
  • Don’t know

Would you be surprised to know that these answers are all wrong. The actual answer of where the weight goes is far more interesting:

Are you ready…

 

You Breathe it out!

Yes that’s right, when you lose weight (specifically body fat) the actual chemical processes that occur mean the large majority of body fat (adipose tissue) is converted to Carbon Dioxide and excreted through the lungs (breathed out).

It literally turns into thin air!

Researchers at the University of New South Wales published this paper in 2014  calculating the exact chemical process that occurs when body fat is “burned” to lose weight. They then performed a novel approach to track the resultant molecule’s path through the body to work out what happened. For those of you interested in the chemistry, the exact formula is:

C55H104O6+78O2→55CO2+52H2O+energy

Triclycerides (body fats) + inspired oxygen >> Carbon Dioxide + energy

When somebody loses 10 kg of fat (triglyceride), 8.4 kg is exhaled as CO2. The remainder of the 28 kg total of CO2 produced is contributed by inhaled oxygen. Lungs are therefore the primary excretory organ for weight loss.
When somebody loses 10 kg of fat (triglyceride), 8.4 kg is exhaled as CO2. The remainder of the 28 kg total of CO2 produced is contributed by inhaled oxygen. Lungs are therefore the primary excretory organ for weight loss. (Source)

To lose 10kg of body fat requires 29kg of inhaled oxygen, and the byproducts are 8.4kg of CO2 and 1.6 kg of water. The researchers proved that the CO2, and part of the water will be exhaled through the lungs, meaning you literally breathe your weight off!

4 time gold medallist Mo Farah Can't believe he's been breathing himself thin all these years.
4 time gold medallist Mo Farah Can’t believe he’s been breathing himself thin all these years.

Wait, does this mean I just need to breathe more to lose weight???

NO of course not. As I said, Weight loss is a billion dollar industry, and everyone is always looking for a quick fix. There are so many different theories and products around, but the best general advice for weight loss is to use more energy than you consume. Eat better/differently/less and be more active. Make healthy lifestyle decisions and be consistent. In short:

Eat Less, Move More.

 

Reference: Meerman R and Brown A. When somebody loses weight, where does the fat go? BMJ 2014;349:g7257

 

Julian Bowen

 

Julian is a Director and Senior Physiotherapist at South Perth Physiotherapy.  He has spent  over a decade working exclusively in private physiotherapy practice, and estimates he would have performed over 35,000 individual treatments in that time. He has worked with everyone from Paralympians,  elite athletes, WAFL Footballers, the Defence Forces and weekend warriors, to thousands of everyday people with all manner of issues.  He is passionate about injury prevention and has a special interest in the treatment of headaches, shoulder issues, hypermobility management and exercise rehabilitation for the prevention and treatment of injuries. 

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