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  1. #1
    Senior Member mkadam68's Avatar
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    Burning Fat or CarboHydrates as Energy

    This issue comes up every once in a while here on C&A. Namely, "How can I burn more fat by riding?" or some-such derivative. Essentially, they ask about the percentage of fat being burned while exercising versus the percentage of carbohydrates being burned (even if they don't put it into these same words).

    I came across this PEZ Cycling article by Matt McNamara (USA Cycling Coach) on fat, carbohydrates, and energy demands. It's good reading if you can understand the technical jargon. (I had to re-read every couple sentences myself to understand. ) The chart below visibly simplifies the concept, so I thought I'd post it here.

    In the end, what it comes down to is our bodies are always burning fat and always burning carbohydrates. It's just that during exercise, the proportion (or percentages) of fat:carbohydrate changes. At easier intensity, the body burns more fat and less carbohydrate. At higher intensities, the body switches over to more carbohydrate. Here's a graph:


    The red line is the burning of fat stores, while the blue is carbohydrate stores (CHO).

    Of interesting note: all athletes, not just us clydes, want to maximize the use of fat stores vs. carbohydrate stores (move that "crossover point" to the right on the graph). The body has only a limited supply Kcals of CHO, but has a large amount of Kcals available in its fat stores. The longer athletes can put off moving to CHO for energy, the longer they can last in the race, period. This might be that concept of "burning matches" we all hear so often about.

    Anyway, thought you all might find it interesting. If someone asks about this again, we can point them to the chart & article.

    Visit The C-Blog : the blog about cycling.

  2. #2
    SpeedFreak
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    So what you're saying is, if you want to burn more fat, do a low intensity workout/ride. However, that would mean taking a much longer ride.
    Palomar01

  3. #3
    Senior Member mkadam68's Avatar
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    Quote Originally Posted by Palomar01 View Post
    So what you're saying is, if you want to burn more fat, do a low intensity workout/ride.
    DOn't just say "more fat". A low-intensity workout gets a higher percentage of its energy from fat sources than carbohydrates (blood sugar).

    Quote Originally Posted by Palomar01 View Post
    However, that would mean taking a much longer ride.
    Yes, but, it's still possible to burn more fat in a high intensity workout than in a low-intensity one (depending on time) because of percentages. For example:

    Hi-Intensity Workout
    60-mins at 1,000kcals/hour
    40% of the kcals from fat
    400kcals of fat burned

    Lo-Intensity Workout
    60-mins at 500kcals/hour
    60% of the kcals from fat
    300kcals of fat burned

    Visit The C-Blog : the blog about cycling.

  4. #4
    SpeedFreak
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    I see. Good information there.

    It does send a good reminder my way that I still have some ways to go to get to my target weight.

    I always thought that during a work out, you are burning carbs you ate last night. However, increasing the intensity, and/or increasing the duration will eventually force your body to start burning fat stores. It was described to me as "catching your 2nd wind" when this begins. It's like you feel you can just keep on going as you are working out.
    Palomar01

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