19 Dec Weight loss, exercise is key!
Want to loose weight? Breathe out.
Source: ABC Science News https://www.abc.net.au/science/articles/2014/12/17/4149911.htm
Instead of focusing on your hips, stomach or thighs for the post-Christmas workout, try paying a bit more attention to your lungs.
Australian researchers have found that the majority of weight lost when we do manage to shed the kilos is actually breathed out as carbon dioxide.
The findings, published today in the British Medical Journal, answer a 100-year old question: where does the fat go when we lose weight?
Lead author Ruben Meerman, physicist, and presenter with ABC TV’s Catalyst, became curious about the question after managing to lose a substantial amount of weight over the course of 2013.
“Being a physicist, I knew that it wasn’t turning into heat but it turns out that most people think that’s where it goes,” says Meerman.
He turned to the biochemistry of fat, and discovered that while the precise chemical formula of fat has been known since 1960 — it’s a mix of carbon, hydrogen, and oxygen — no one had quantified exactly what happens to all the atoms that make up fat when it is burned off during activity.
“You know that all of the carbon in it is going to become carbon dioxide, and the other thing it becomes is water so you know all the hydrogen in fat will become water, but what’s not clear at all is what’s going to happen to the oxygen atoms that are part of the fat molecule,” Meerman says.
After four months of research, Meerman and co-author Professor Andrew Brown from the University of New South Wales discovered the final piece of the puzzle, buried in a journal article published back in 1949.
This showed that the oxygen atoms are shared between the carbon dioxide and water in a ratio of 2:1, so four oxygen atoms are exhaled, and two are excreted in bodily fluids such as sweat, tears and urine.
This gave the researchers a final figure of 84 per cent of atoms that make up a fat molecule exhaled as carbon dioxide, and the remaining 16 per cent lost through water.
Their analysis also showed that for every 10 kilograms of fat being ‘lost’ or oxidised, the body actually needs an additional 29 kilograms of oxygen, with the resulting output of 28 kilograms of carbon dioxide, and 11 kilograms of water.
Exercise key
While the findings answer a fundamental question about the biochemistry of weight loss, unfortunately it does not mean that simply breathing faster is the new key to shedding extra kilos.
“If you sit still in a chair and you start breathing more than required, that’s hyperventilation and you’ll get tingly fingers and palpitations and if you keep going too long you’ll faint,” Meerman says.
“The breathing faster is definitely what you need to do, but you have to do it because your body needs to get rid of more carbon dioxide because you’re exercising.”
The paper shows that only a relatively small amount of weight is lost as exhaled carbon dioxide on a typical sedentary day — typically around 200 grams for a 70 kilogram adult — and that will only increase with physical activity.
“You can only breathe so many times a day; on a day of rest, you breathe around 12 times a minute so 17,280 times you’ll breathe in a day and each one takes 10 milligrams of carbon with it, roughly,” Meerman says.
“So there’s your limit on how much you’re going to lose in a day with no exercise.”