The Fat Burning Zone is a Lie: Do This Instead

You’ve probably seen the charts on cardio machines — the “fat-burning zone” that promises optimal fat loss if you keep your heart rate in a certain range. It sounds great in theory… but in reality, it’s misleading.

Your body is always burning a mix of carbs and fat for fuel — the ratio just shifts depending on how hard you’re working.

At lower intensities you burn more fat percentage-wise, but fewer total calories, while at higher intensities you burn more carbs in the moment, but you create a bigger overall calorie deficit that leads to greater fat loss over time.

Understanding this simple shift can be the difference between spinning your wheels and finally seeing fat loss results.

Why the Fat-Burning Zone Misleads You

At lower intensities (generally less than 65% VO2 max), fat does contribute more fuel, but the overall calorie burn is modest.‌¹

For example: if you jog slowly in the so-called “fat-burning zone,” you might burn 200 calories in a long session. Even if 60% comes from fat, that’s just 120 calories from fat.

Compare that to a shorter, harder workout where you burn 500 calories — even if only 40% comes from fat, that’s 200 fat calories.

More total calories, more fat burned, and in less time.

Even more important: HIIT (high-intensity interval training) doesn’t just burn calories while you’re working — it also increases your post-exercise oxygen consumption (EPOC). That means your metabolism stays slightly elevated after training.

Of note, the effect is smaller than many fitness myths suggest — research shows it’s typically only 6–15% of the calories burned during the workout itself — but combined with the higher calorie burn during HIIT, it still makes these sessions more efficient for fat loss compared to steady-state cardio.^2,3

A Smarter & More Efficient Way to Burn Fat

Instead of spending hours slogging away in the “fat-burning zone,” try adding HIIT sessions to your week. Research shows HIIT is not only time-efficient but can improve cardiovascular fitness and fat loss more effectively than steady-state cardio.⁴

Here’s an example of a great 15-20 minute workout that will keep your metabolism revved up:

1️⃣ Warm up with cardio and mobility for 3-5 min.

☝️Do not skip the warm up! Warming up prevents injury and makes the workout way more effective.

2️⃣ Perform 10 rounds of 20 sec all out effort + 40 seconds rest. Choose one or more of the following exercises:

Sprints
Kettlebell / dumbbell swings
Squat jumps / Squat Jacks / box jumps
Dumbbell squat presses
Mountain climbers
Burpees

3️⃣ Finish with a 3–5 min cooldown walk to bring the heart rate back down.

Bottom Line: Intensity is the Answer

The “fat-burning zone” is outdated advice. There is definitely a time and a place for lower intensity cardio and general movement, but if your goal is fat loss and body transformation, higher intensity is a more effective way to get results.

Mixing in HIIT sessions — alongside strength training and balanced nutrition — will get you closer to the results you actually want.

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References:

Spriet LL, Randell RK. Fat is the dominant energy source at low aerobic power outputs (< 40% VO₂max) and provides about half the energy during moderate-intensity exercise (~40–65% VO₂max). Sports Science Exchange, 2020;205.
LaForgia J, Withers RT, Gore CJ. Effects of exercise intensity and duration on the excess post-exercise oxygen consumption. J Sports Sci. 2006 Dec;24(12):1247-64. doi: 10.1080/02640410600552064. PMID: 17101527. https://pubmed.ncbi.nlm.nih.gov/17101527/
Boutcher SH. High-intensity intermittent exercise and fat loss. J Obes. 2011;2011:868305. doi:10.1155/2011/868305.
Keating SE, Johnson NA, Mielke GI, Coombes JS. A systematic review and meta-analysis of HIIT vs. moderate-intensity continuous training for cardio-metabolic health. Obes Rev. 2017;18(8):943–961. doi:10.1111/obr.12536.