Don’t Confuse Fat Oxidation with Body Fat Loss

Egis R.
4 min readApr 19, 2023
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It pisses me off when some keto marketroid says ‘Oh you need to go on a fat eating spree you’ll become keto-adapted and burn an ass-load of fat for energy yay keto is the best.’ Intermittent fasting lover who goes all ‘Yeah you know when you’re in a fasting state your body starts burning fat instead of storing it’ is dumb as a bucket too.

Whether you oxidize (“burn”) more fat or carbs is utterly irrelevant when it comes to losing body fat because…

Fat oxidation is not the same as body fat loss

Fat oxidation or “burning” is the process of breaking triglycerides into smaller molecules that can then be used as a source of energy to fuel your life. Body fat loss on the other hand is the process of fat mass decreasing over time.

Yay science.

But here’s the deal: Burning fat for energy and losing body fat, even though they sound the same, are two different things. As Layne Norton, PhD in Nutritional Sciences, once wrote:

If something causes more fat to be oxidized, it does not mean it will result in total body fat decreasing. It just means that fat is being used as a fuel source.
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I feel like you’d appreciate a few examples. Here goes.

When you’re on a high-fat diet such as keto or Atkins you burn more fat because you’re eating more dietary fat (you’re also storing more fat). But it doesn’t necessarily translate to changes in body composition or body fat loss in our case.

What matters for fat loss is the net fat balance (the difference between fat oxidation and fat storage) which is governed by overall energy balance aka calories in versus calories out by the end of the day, week, month, and eventually year:

If fat oxidation > fat storage = fat loss | If fat storage > fat oxidation = fat gain | If fat oxidation = fat storage = weight maintenance
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Think rationally: If burning fat was the only thing that mattered for fat loss, everyone on a keto diet would be shredded to the bone. But that’s not what we see.

Now, intermittent fasting. Quoting the article I found on the all-powerful Google, “By 12 hours (i.e. of fasting), you’ve entered the metabolic state

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Egis R.

I’m Egis, an online weight loss coach who has heightened BS sensors for fitness & nutrition. Only evidence-based & sustainable fat loss. www.absscience.com