Fat Burning Zone Myth; Going Slower Burns More Fat

I was teaching a boot camp the other day and, while encouraging a participant to work at a higher intensity, was hit with the question that never seems to quit. “But don’t I burn more fat going slower?” Well, why wouldn’t people believe that? It’s listed right there on most of the cardio machines: Fat Burning Zone (below cardio training zone). But, that’s misleading.

Let’s get to the heart of this, shall we? What the real deal is, is that you are NOT burning more fat. You’re burning a higher % of calories from fat. But, as you can see from the table below, when you look at two different intensity levels (55% and 85% of max heart rate), while a higher % of calories burned comes from fat at the lower intensity (58% vs 42%) you aren’t burning as many calories at a lower intensity level (209.8 vs 457.1). Ultimately you don’t burn as many fat calories (121.1 vs 191.3).

So, while going a slower, easier pace sounded good, it just doesn’t give the same benefits as a more intense program. For bigger losses, you need to go for bigger effort. Higher intensities will give greater fat loss results.

%Heart Rate	Total Calories	Fat Calories	Carbohydrate Calories
55%	209.8	121.1	88.7
85%	457.1	191.3	265.8

Table from Len Kravitz, PhD article “Fat Facts”