Once upon a time, Ruben Meerman lost 15 kg (more than 30 pounds) and wondered where the weight had gone. The doctors he asked didn’t seem to know. He conducted a survey of 150 health professionals, of whom “more than half thought that fat was converted into heat or energy.” But as a physicist, he found this theory to be in conflict with the Law of Conservation of Mass.
Meerman joined forces with the man who runs the School of Biotechnology and Biomolecular Sciences at the University of New South Wales. After arduous research, Andrew Brown found the game-changing clue—a formula in a 1949 scientific paper which stated that “oxygen atoms are shared between the carbon and hydrogen in fat at a ratio of 2:1.” The study authors say:
People who wish to lose weight while maintaining their fat-free mass are, biochemically speaking, attempting to metabolise the triglycerides stored in their adipocytes…The complete oxidation of a single triglyceride molecule involves many enzymes and biochemical steps…
After biomolecular reactions have divvied them up, some of the oxygen atoms will bond with different atoms to become water, and twice as many will end up as part of carbon dioxide. In other words, “The correct answer is that most of the mass is breathed out as carbon dioxide. It goes into thin air.” The other component, water, is disposed of in the ways usual for liquids. The bladder, sweat glands, and tear ducts are fat’s secondary organs of excretion. “The lungs are the primary excretory organ for fat.” So says the study, which was published in the British Medical Journal. Meerman and Brown wrote:
To calculate these values, we traced every atom’s pathway out of the body.
Stoichiometry shows that complete oxidation of 10 kg of human fat requires 29 kg of inhaled oxygen producing 28 kg of CO2 and 11 kg of H2O. This tells us the metabolic fate of fat but remains silent about the proportions of the mass stored in those 10 kg of fat that depart as carbon dioxide or water during weight loss.
When people eat more than they need, proteins and carbohydrates get changed into triglycerides, which are then “stored in lipid droplets inside fat cells.” Until they are liberated, and their carbon set free, no weight is lost. But once the triglycerides have been broken down, the fat is no longer fat.
When the broken-down fat can be induced to leave the body, it makes its departure in the form of H2O and CO2. For a person to “lose” 22 pounds, 64 pounds of inhaled oxygen have to be brought in, making a combined total of 86 pounds of stuff. For this alchemy to take place requires the expenditure of 94,000 calories, and the end product is 24 pounds of water and almost 62 pounds of carbon dioxide (also totaling 86 pounds.) All this can be more easily assimilated via Ruben Meerman’s TED talk on “The Mathematics of Weight Loss.”
What about the widespread yet erroneous belief that fat is converted to energy or heat? The study authors say:
We suspect this misconception is caused by the “energy in/energy out” mantra and the focus on energy production in university biochemistry courses. Other misconceptions were that the metabolites of fat are excreted in the faeces or converted to muscle.
Losing weight requires unlocking the carbon stored in fat cells, thus reinforcing that often heard refrain of “eat less, move more.”…A single 100 g muffin represents about 20% of an average person’s total daily energy requirement. Physical activity as a weight loss strategy is, therefore, easily foiled by relatively small quantities of excess food.
That last line is quite important for anyone who works out and then fills up on the “I deserve it” theory. Deserving or no, it takes only a small bit of nibbling to negate the good effects of what seemed like a monumental amount of exertion. Ignoring this amounts to self-sabotage.
Your responses and feedback are welcome!
Source: “This is where body fat ends up when you lose weight,” ScienceAlert.com, 12/17/14
Source: “When somebody loses weight, where does the fat go?,” BMJ.com,12/16/14
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