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.
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:
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:
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 called ketosis. In this state, your body starts to break down and burn fat. By 18 hours, you’ve switched to fat-burning mode and are generating significant ketones.”
Yet again the author is throwing “burn fat” and “fat-burning mode” terms around to promote her fasting tracker app and lure you into fasting your guts out.
Sure, you may burn more fat than carbohydrates during a fasting window. But guess what happens when you eat a lot of food in a short period of time aka eating window? You store a lot of fat.
Focusing only on what fuel gets burned during a fasting window is only part of the picture. What about the other few hours of the day when you don’t fast? If you’re not in a calorie deficit by the end of the day, week, or month, it doesn’t matter how much fat you burn.
But let’s not stop there because we need to free fasted cardio proponents from shuffling on the treadmill first thing in the morning on an empty stomach.
These early risers believe that they’ll lose more body fat due to the greater rate of fat burning that happens during exercise in an overnight fasted state. To quote the study by Schoenfeld and colleagues:
The same can be said about the so-called “fat-burning zone” which states that if you exercise at a specific intensity, you’ll use more fat for fuel and lose more body fat. While it sounds sexy, the “lose more body fat” part just isn’t true and I wrote all about it here.
Sure, fat burning will be higher during that hour or so of exercise but what about the other twenty-three hours of the day? Well, your body adapts to spare fat throughout the rest of the day and burns more carbohydrates (source one, source two).
Even though you might be using more fat than carbs to fuel exercise and everyday life, it doesn’t mean you’re losing body fat because fat loss is a matter of sustaining a calorie deficit for a long period of time.
So don’t fall for numbskulls who promote diets, supplements, and exercise styles that lead to greater fat burning/oxidation. When we’re talking about metabolism, that’s not the same as losing stored body fat.
Thus, when it comes to nutrition, if your goal is weight loss, ask yourself these two questions:
- What adjustments to my diet do I need to make to put myself in a sustainable calorie deficit? Reduce liquid calories? Moderate snacking, alcohol, sauces?
- How can I add more whole, minimally-processed foods to my diet to sustain that calorie deficit easier? Eat more fruits, vegetables, and protein-rich foods? Drink more water?
And if you want to bypass all of the nonsensical weight loss information and avoid common beginner mistakes, apply for the 1:1 Coaching Program where my goal is to be at your side the entire way, helping you to avoid scams and pitfalls that most people fall into.
Originally published by me on Medium on April 19, 2023