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What happens with fats after exercise?

  1. Jan 9, 2014 #1
    I know that we use fat and other molecules to store energy, and that during exercise we use that energy.
    I understand that we use that energy by means of a chemical reaction that, among other things, transforms fat in something else.

    What I wonder is: what is fat ultimately transformed to and what does the body do with it?, my guess is that is throw away in the urine.

    Thanks a lot
  2. jcsd
  3. Jan 9, 2014 #2


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    Staff: Mentor

    Carbon dioxide and water.

    It is not that much different from burning, just through another pathways.
  4. Jan 9, 2014 #3


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    Homework Helper
    Gold Member

    Yes, that's frankly an every schoolchild knows question and answer. A proper answer of how that happens is several chapters of a biochemistry book, so too generic for here.

    Since you did come here I'll tell you something not everybody realises - the water mentioned by Borek can be important. For instance the hump of the camel is a store of fat not water, and oxidising that gives it the water it needs to see it through its waterless times.
  5. Jan 10, 2014 #4
    Energy is released when fatty acids are oxidized. We could oxidize fats by literally burning them and this would release energy but our bodies use a complex series of enzymes to achieve the same goal. Excluding transport, the first part of this process is called beta oxidation and happens in the mitochondria. It's a complex process but to put it into very simple terms, the fatty acid molecule is broken down to generate molecules of acetyl-CoA. The acetyl-CoA molecules then enter another cycle called the citric acid cycle where they are are further oxidized to carbon dioxide. This generates NADH and FADH2. NADH and FADH2 are then used in the electron transport chain to produce ATP, the energy currency of the cell.

    The actual process is much more complicated and involves many enzymes and multiple reaction steps. Here is a slightly more detailed (but still very simplified) explanation:

    http://www.biocarta.com/pathfiles/betaoxidationpathway.asp [Broken]

    Oh, and a fat molecule is basically glycerol and three fatty acids. The glycerol portion can be converted into glucose for fuel while the three fatty acids undergo beta oxidation as mentioned above. Wikipedia has a very detailed explanation of all of the steps involved from start to finish. A college textbook would also show the individual steps - but with significantly less detail.
    Last edited by a moderator: May 6, 2017
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