Science Daily’s New Fat Myth: Fat is Converted to Carbon Dioxide
An article appearing last week on the Science Daily website makes the outrageous claim that body fat is converted to carbon dioxide and water. This new fat myth is probably less harmful than many other myths associated with weight loss, but that is only because no one has come up with a way to monetize the belief that fat is converted to carbon dioxide in the body…yet.
The article in question, “When you lose weight, where does the fat go? Most of the mass is breathed out as carbon dioxide, study shows,” starts off with the statement: “The most common misconception among doctors, dieticians and personal trainers is that the missing mass has been converted into energy or heat.”
Unfortunately for Science Daily, that is exactly what happens in the human body when fat is metabolized: the fat is converted into energy, so any article that starts off by rejecting that basic fact – that fat is not metabolized into energy – has already lost credibility.
The human body is a clever organism. When you are eating normally, it takes in protein, carbohydrates, and sugars (which, of course, are complex carbohydrates), converts the protein into body tissue and converts the carbohydrates and other dietary sugars into the glucose that goes into the bloodstream and eventually passes into the body cells that burn the glucose to create energy. So far, so good. When the body’s reserves of ready calories from blood sugar have been exhausted, usually during the overnight hours while we are sleeping, the body metabolizes fat into blood sugar and uses the blood sugar liberated from the fat through that process to provide fuel for the body.
Not so fast, according to the study’s lead author, Ruben Meerman, a physicist and Australian TV science presenter. “The correct answer is that most of the mass is breathed out as carbon dioxide. It goes into thin air.” That’s true, but it is also irrelevant to weight loss, and misleading because it suggests that body fat is converted into CO2 and H2O, but that’s not true. The body breaks down the fat into glucose, and the glucose is turned into carbon dioxide and water as the energy in the glucose is used as fuel by the body.
Professor Andrew Brown, head of the UNSW (University of New South Wales) School of Biotechnology and Biomolecular Sciences, who contributed to the study, has said that,”There is surprising ignorance and confusion about the metabolic process of weight loss.” That is certainly been proven true….by this article.
Science Daily isn’t actually a scholarly journal, although it masquerades as one. It looks like the online version of a scholarly journal, but it carries advertising, something real journals never do and it is actually a compendium of press releases that are neither vetted by anyone nor peer reviewed. It is not clear whether they actually charge to publish press releases, but other online journals often charge an upfront fee to publish research reports, which does severe damage to their impartiality. Because Science Daily carries paid advertising, it is not likely that they are charging contributors to publish their articles; the articles justify their advertising rates by attracting traffic to their pages, and the advertisers pay the freight. The original article upon which the release was based was published by BMJ (British Medical Journal), which is a professional, peer-reviewed journal.
The bottom line on this story is simple. Sometimes, a study really isn’t worth the effort and, in this case, there was really very little effort involved, since all this study does is reiterate known facts of very little use to anyone embroiled in a weight-loss struggle.
01/06/2015 @ 7:21 pm
It is true that mass and energy can be equated, as described by Einstein’s famous equation: E=mc2. However, the conversion of mass to energy is not a useful description of weight loss that occurs when fat is metabolized. Fat molecules are made mostly from carbon and hydrogen atoms. The mass to energy conversion approach to weight loss would require the carbon and hydrogen nuclei to be converted to energy in order to remove the weight of these atoms (over 99% of the weight of atoms is in the nuclei, with the electrons bound to the nuclei comprising a very small amount of the mass). If such a nuclear reaction were to occur, the energy released from just one gram of fat would be HUGE, over 20 billion calories. However, there is no nuclear reaction converting the carbon and hydrogen atoms of the fat molecules into energy inside the human body, and it is not conversion of the carbon and hydrogen nuclei to energy that is responsible for the weight loss associated with fat metabolism. So where does the weight of the fat molecules go?
During fat metabolism, the carbon and hydrogen atoms that made up the fat molecule are chemically converted to other molecules, and it is the chemical energy that can be harnessed by the body to be used for things like riding bicycles. It is the chemical energy associated with the fat molecule, not the nuclear energy, that is useful to the body.
The energy released from fat metabolism is derived from a string of chemical reactions that occur as fatty acids are broken down to acetyl-CoA, and then more energy is released as the acetyl-CoA goes through a chain of reactions that require oxygen, and release carbon dioxide and water. The carbon dioxide is removed in the air you exhale. So your body gets energy from the chemical reactions that breakdown the fat molecule, and since your body needs to get rid of the leftovers from the reaction (carbon dioxide and water), it happens that you lose weight… when you exhale. Inhale an oxygen molecule (mass = 32 amu) and exhale a carbon dioxide molecule (mass=44 amu). The extra mass you exhale is due to the oxygen you inhaled having combined with carbon from fat, carbohydrates, or proteins that the body converted to acetyl-CoA.
So why is losing weight so hard – if all you have to do is exhale? Because first the body has to run the fat molecules through the chemical process to extract the energy, creating the leftovers, carbon dioxide and water. Then when you exhale, the carbon dioxide molecules that get chunked out into the atmosphere are derived from fat. Typically the body would rather keep the fat until the chemical energy stored in it is really, really needed. So the hard part of dieting is convincing the body that it really needs the precious energy stored in the fat molecules badly enough to break down those fat molecules into carbon dioxide and water. Exercise can help, dieting can help, even certain hormones may help, but as many dieters know, convincing the body it needs to break down fat molecules is not easy!
01/07/2015 @ 11:55 am
That’s one of the longest replies I’ve ever received, but it still misses the point. Fat isn’t metabolized into carbon dioxide and water. Fat is metabolized into blood glucose which, in turn, is used by the body as fuel. This might be a distinction without a difference, unless you take into account the process through which fat becomes metabolized. Stored fat isn’t converted into glucose as long as the body has other fuel sources, such as the daily intake of carbohydrates, which is precisely the same point you make in your last paragraph, bringing us together ultimately to the same conclusion. As long as the body has other fuel resources, it simply doesn’t want to part with that fat. Ultimately, then, what value does the original article have in terms of the weight loss debate…which was my primary point.
02/25/2017 @ 8:10 pm
Joan didnt said that fat is metabolized to water and CO2, in resume she or he is only saying that is a byproduct of other metabolic process.
08/01/2016 @ 7:39 pm
Energy is NOT itself ANYTHING. YOu are laughably science/physics illiterate. NO reaction EVER turns matter into energy, you foolish person. Message me privately for more.
12/07/2016 @ 9:44 pm
Yeah, fat isn’t turned into glucose either, bro (ever). It’s turned into acetyl-CoA, which then enters the citric acid cycle and produces ATP (energy), water, and CO2. But glucose can be converted to fat.