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  • I am a Fat-Burning Machine, Verified by a VO2max Test: 44% fat at 91% VO2max

    A few months ago, I signed up to be part of a study at Colorado State University (CSU.) Researchers from CSU and University of Colorado health are examining how high levels of exercise affect your heart. I have gone through two of the three phases of testing.

    One of the tests is a VO2max test. Though the researchers are not looking for substrate use (the percentage of carbohydrate and fat used at each exercise intensity), these numbers show up on the results sheet.

    The research coordinator, Nate Bachman, sent me this result:

    “I am also attaching a report of your VO2 Max test and a substrate report.  The substrate report indicates both % and grams per minute of carbohydrate and fat you used throughout the test (and the corresponding VO2 value).  These numbers fluctuate due during each stage due to slight changes in effort, breathing pattern, and measurement variability.  You can go through the report and look at different time points.  At 5:01 you were using 44% fat and your VO2 was 43.0 ml/kg/m (43.0/47.3= 91% of your max).  This indicates you were using fat for almost half of your fuel source at 91% of max- this is great.”

    I don’t know how I compare to others in the study, but I do know some baseline information. There is something called the Crossover Point Hypothesis, developed and studied by George Brooks at UC Berkley. The study was looking for the point where athletes would crossover from burning primarily fat to carbohydrates. As you probably know, at low-intensity exercise fat is the primary source of fuel.

    The investigation by Brooks showed that depending on the level of training, athletes would crossover somewhere between 35% and 65% of VO2max.

    More recently, Jeff Volek’s research pointed out that the crossover point has a direct relationship to diet. In a past blog, I noted that elite ultrarunners consuming an extremely high-fat diet (some 70% of daily calories come from fat) have shifted the paradigm about what is possible for fat burning for endurance athletes.

    I also noted in that blog that I am not interested in following a 70% fat diet. My diet follows Fat-Burning Machine principles and I modify those principles depending on my level of activity. The Fat-Burning Machine plan is different from Keto or Paleo in that it allows limited grains, dairy, fruit, and alcohol. Portion size, the timing of macronutrients and exercise considerations all play a role.

    Over the years that I’ve been eating the Fat-Burning Machine way, I knew it made a difference because I didn’t need to supplement much nutrition during training and racing. Now I have solid proof that I am a Fat-Burning Machine.

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