100,000 calories in fat storage

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  • #15290


    in the book, you state that there are more than 100,000 calories stored in fat to burn even in a lean athlete.
    It I take Steve House’s essay on page 287 of the book, he weighed 77 kg and had a body fat percentage of 5.6 percent, which would give him 4.3 kg of body fat. You often read that 1 kg of body fat has 7,000 calories (as it contains also some water), so Steve would have 30,100 calories stored in fat. As you will still need fat around your organs to be healthy or even just survive, a lot of these calories won’t be usable to burn (3-4 percent are considered necessary according to Wikipedia).
    So how do you get to your 100,000 calories? Are they stored somewhere where body fat percentage doesn’t account for it? I do know that you also store lipids in the muscle cells, but is it that much?

    Would you still say a body fat percentage of 5.6 is okay if you, say, go on a 14 day outing where you will have a caloric deficit of 2000 calories each day? Or would you have an approximation of an “ideal” body fat percentage for longer outings in a caloric deficit?

    Best regards


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    Anonymous on #15345

    You ask a good question and I can’t answer it. I have used multiple exercise science references that seem to agrees on the 100,000kcal number for total fat stores in endurance trained athletes.

    But, let’s start with some areas we do know:

    1KG of fat contains 9,000kcal because 1gm of fat contains 9kcal of energy. The water you mention contains no energy so should not be included in your calculation.
    At 5.6% of 77kg Steve was carrying 4.3kg of adipose fat. This fat contained almost 39,000kcal of energy.

    We also know that well endurance trained athletes can store much more energy as intramuscular fat than non trained people. I cannot find sources that show what this amount is but even the leanest marathon runners are said to carry this 100,000kcal of fat. I have always assumed that this must be in the form of increased intramuscular fat.

    14 days x 2000kcal = 28,000 kcal used. I’m not any kind of authority on this subject but can tell you that you will loose a lot of body mass.

    I suggest doing shorter trips with similar energy balance and seeing how much mass you lose.


    Jan on #15350

    Hi Scott,

    thanks for your answer!

    About the calories of body fat, here is a “resource” in English I just googled quickly: Calories in body fat
    I found some sources in German which seem a bit more serious, but the point is the same: Body fat is not pure fat.

    Also, you should definitely consider that you can’t burn all the fat you have.

    I am nowhere near 5.6 % body fat, and the fact that you can’t answer my question precisely will luckily keep me from going that route. I think a body fat percentage of 10-12 might be ideal for my normal 10-14 day outings in a rather big caloric deficit, though I’m really just guessing here.

    If anyone is interested: Here is a site from a nutritionist and hiker who gives some advices and insights in nutrition for long-distance hikes. It made me change my diet from eating mostly very fatty food to a more balanced approach, and it definitely helps me keep my muscle mass on longer outings. Probably because my body transformed my muscles to carbs before (gluconeogenesis).
    An interesting point of her for the “gel”-guys:
    “If you eat sugar, hormones and enzymes alike adjust to burn sugar and will lock fat in storage. Simply stated: Eat fat, burn fat. Eat sugar, burn sugar. If you want to burn fat, avoid sugar. Instead, eat fat mixed with protein and complex carbohydrates.”

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