Carb binges and fat adaptation

  • Creator
  • #9637

    Hi Gurus,

    What is the effect of eating extra carbs once in a while on the process of fat adaptation.
    Does the entire process gets reset ?
    I even read in some articles online that cheating once a week is actually beneficial.
    kindly let me know your views.


Posted In: Nutrition

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    copilot67 on #9672

    I think this is a very good question bevause
    even if I go on a high fat/low carb nutrition your body should still be capable of „using“ carbs to generate energy. Especially in situations where only carbs are easily available (high altitude expeditions etc)
    The other point is that high fat diets have shown to increase fat adaption / utilisation in studies but with the drawback of using more oxygen to produce the needed ATP.
    Is this a thing to consider when going to high altitude where the oxygen pressure drops below a critical point meaning less oxygen is available?

    Anonymous on #9721

    @Kedar; It depends on how well fat adapted you are and how frequent and how long your binges are. The adaptations we are talking about are enzymatic and occur relatively quickly. In our non-fat adapted clients who adopt a moderate dietary shift along with a high volume of Aerobic work we see significant changes in their energy levels and need for carbs in even two weeks and big changes in 6 weeks. Fro my personal experience of being pretty well fat adapted for many years, falling off the wagon and reverting to more carb dependence seems to happen much faster. If I let me diet shift to more carbs than normal I notice it in just a few days of lapsing. A couple of long fasted runs seems to help get me back on track pretty quickly though. You can do a simple experiment on yourself to see how carb dependent you’ve become by doing one of your typical workouts after the binging and see if it affects your energy.

    You are technically correct but I don’t think it is quite so simple.
    You are correct that the oxidation of fatty acids (called beta oxidation) to produce the acetyl CoA needed for the Krebs cycle does require oxygen and the acetyl CoA produced from pyruvate does not. Both of these processes occur in the cytosol. Acetyl CoA is the starting molecule for aerobic metabolism which takes place in the mitochondria. But the important thing to keep in mind is that the the beta oxidation production of acetyl CoA is vastly more energetic that the glycolytic process for producing acetyl CoA. Something like 3-5x more ATP is produced depending on the fatty acid being oxidized. So, while some more O2 is required for the beta oxidation, a whole bunch more energy is the result. Even a highly endurance trained individual can only store a maximum of about 2000kcal of glycogen vs 100,000kcal of fat. You can burn though 2000Kcal in 2-3 hours of fairly intense exercise before the wheels come off. Mountaineering and ultra distance events are not conducted at high intensity but a poorly fat adapted athlete will be blowing through that glycogen storage at a rate 2-3 times as fast as the fat adapted athlete will. The wheels will come off a lot sooner for the poorly fat adapted athlete unless he/she can find a way to replace those kcals as fast as they are being used up. This is not an easy thing to do during heavy exercise and at high altitude.


    Kedar_dg on #9738

    Thanks Scott for clarifying !

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