What FatMax actually is
FatMax is the exercise intensity at which your body oxidises fat fastest, measured in grams per minute. Achten, Gleeson and Jeukendrup established it in 2002 by testing 18 moderately trained cyclists on a stepwise protocol: fat oxidation peaked at 64% of VO2max, equivalent to 74% of maximum heart rate, at 0.60 grams of fat per minute.
That is higher than most people expect, and higher than the band treadmills and cross-trainers print on the console. The marketed zone sits around 60 to 70% of maximum heart rate, which is below where the measured peak actually falls.
Percentage is not the same as total
Both claims are true and they get confused constantly. At very low intensity a larger share of your energy comes from fat, sometimes above 60%. At FatMax a smaller share comes from fat, but the total grams per minute is higher, because you are burning far more energy overall.
Walking might take 55% of its energy from fat at 5 kcal per minute. A steady ride might take 40% from fat at 11 kcal per minute. The second burns more fat, despite the lower percentage. Optimising the percentage is optimising the wrong number.
What this means for losing fat
Body composition follows total energy balance across weeks, not which band a single session sat in. A harder session burns more total calories in the same time and leaves a longer post-exercise elevation. Neither effect is large, which is why diet decides most of the outcome.
The real case for training near FatMax is performance, not weight. A high fat-oxidation rate spares glycogen, which is what lets you hold pace late in a long event. That is also why it responds to training: fat oxidation rises with aerobic volume, and trained athletes reach their peak at higher intensities than untrained ones.
How to find your own FatMax
The calculator gives a population estimate. Individual FatMax varies widely, so treat the number as a starting point and narrow it with your own data.
- 1
Anchor to a measured maximum
Every percentage here is a share of your maximum heart rate, so a wrong maximum moves the whole band. Use a measured value from a hard effort rather than an age formula if you have one.
- 2
Ride or run the band for 30 minutes
Hold the estimated range on flat ground in mild conditions. It should feel steady and purposeful, short sentences rather than silence, and be repeatable the next day.
- 3
Judge it by fuel, not feel alone
At or below FatMax a long session should not need much carbohydrate to stay comfortable. Needing to eat early is a sign you are working above it.
- 4
Get it measured if it matters
A metabolic cart test with a stepwise protocol is the only way to know your FatMax rather than estimate it. Worth it for long-course athletes, unnecessary for general fitness.
Worked example
An athlete with a measured maximum heart rate of 190 bpm:
| Estimated FatMax (74%) | 141 bpm |
| FatMax zone (68 to 79%) | 129–150 bpm |
| Marketed "fat burning zone" (60 to 70%) | 114–133 bpm |
The marketed band tops out eight beats below the measured peak. Training there is not wasted, it is just easier than advertised and burns less fat per minute than the band above it.
Frequently asked questions
What heart rate burns the most fat?
Fat oxidation peaks near 74% of maximum heart rate, about 141 bpm for a 190 bpm maximum. That figure comes from Achten, Gleeson and Jeukendrup (2002), who measured peak fat oxidation at 64% of VO2max in trained cyclists. Individual values vary by roughly 10 percentage points either side.
Is the fat burning zone a myth?
The zone is real, the marketing around it is not. Fat oxidation does peak at a specific moderate intensity, but it peaks higher than gym equipment suggests, and training there is not the fastest way to lose fat. Total energy balance across the week decides that.
Should I train in the fat burning zone to lose weight?
Only if you enjoy it or need the low stress. For weight loss, what matters is total energy expenditure and diet, and harder sessions burn more calories per minute. Train near FatMax for endurance performance, because sparing glycogen is what holds pace late in long events.
Does the fat burning zone change as I get fitter?
Yes. Trained athletes oxidise fat faster and reach their peak at a higher percentage of maximum, while the general population peaks nearer 47 to 52% of VO2max. Aerobic volume is what moves it, which is the least glamorous training there is.
Is FatMax the same as Zone 2?
They overlap but are not identical. Zone 2 is a band defined by training models, while FatMax is a single measured intensity where fat oxidation peaks. FatMax usually sits at the top of Zone 2 or just above it, closer to the first lactate threshold than to easy recovery pace.
Sources
- Achten, Gleeson & Jeukendrup (2002). Determination of the exercise intensity that elicits maximal fat oxidation. Medicine & Science in Sports & Exercise 34(1):92-97. Peak fat oxidation 0.60 ± 0.07 g/min at 64 ± 4% VO2max (74 ± 3% HRmax); Fatmax zone 68 ± 3 to 79 ± 3% HRmax; negligible above 92 ± 1% HRmax. Link
- Achten & Jeukendrup (2004). Optimizing fat oxidation through exercise and diet. Nutrition 20(7-8):716-727. Link
- Maunder, Plews & Kilding (2018). Contextualising maximal fat oxidation during exercise: determinants and normative values. Frontiers in Physiology 9:599. Link
- What Heart Rate Zone Should You Train In?Which heart-rate zone to train in and when: most time easy in Zone 2, a controlled dose at threshold, a little in Zone 5. Plus how to find your zones.
- Zone 2 Heart Rate, ExplainedWhat Zone 2 training is, why it builds your aerobic base, how to find your own Zone 2 heart rate with the talk test, LT1 or MAF, and how much of it to do.