As part of a study on this particular topic, scientists from the University of New South Wales posed a very simple question to health professionals: when somebody loses weight, where does the fat go? Of the 150 dietitians, doctors, and personal trainers that the surveyed, they said that only three respondents answered the question correctly.
Writing for “The Conversation,” assistant scientists Ruben Meerman and Andrew Brown, professor and head of biotechnology and biomolecular sciences at UNSW, explained the results of the research – and just like the health professionals who were questioned, you might be surprised at what they found.
They wrote: “the most common misconception by far was that fat is converted to energy. The problem with this theory is that it violates the law of conservation of matter, which all chemical reactions obey.” Other respondents believed that fat was converted into muscle, which, they explained “is impossible.” Another theory was that it leaves the body through the colon, which was also proven to be incorrect.
So what’s the answer then?
“Fat is converted to carbon dioxide and water. You exhale the carbon dioxide and the water mixes into your circulation until it’s lost in urine or sweat. If you lose 10 kg (22 lbs) of fat, precisely 8.4 kg (18.5 lbs) comes out through your lungs and the remaining 1.6 kg (3.5 lbs) turns into water. In other words, nearly all the weight we lose is exhaled.”
While this might surprise people, almost everything that we eat comes back out via the lungs. For example, all the carbohydrates you digest and nearly all the fats are converted to water and carbon dioxide. The same goes for protein and alcohol, apart from a small amount of the former that is turned into urea and other solids, and excreted as urine.
The scientists pointed out that the only food that makes it to your colon undigested is dietary fiber, such as sweetcorn. The rest is absorbed into the bloodstream and organs.
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