“You have to train in the 'fat-burning zone' to lose fat.”
You have to train in the 'fat-burning zone' to lose fat.
Total energy expended beats the fuel mix used during the session.
Pooling 28 trials, interval training and steady moderate cardio produced statistically indistinguishable changes in body fat. The fuel you burn mid-session does not determine the fat you lose over months.
Where the myth comes from
It's a real observation misapplied. At roughly 60–65% of maximum heart rate, the highest *proportion* of energy comes from fat. Gym cardio machines print this as a 'fat-burning zone', implying that going harder somehow protects your fat stores.
Percentages versus totals
A slow walk might be 60% fat-fuelled but burn 250 kcal an hour, giving 150 kcal from fat. A hard run might be 35% fat-fuelled while burning 700 kcal, giving 245 kcal from fat — plus a much larger total energy cost. And because the body rebalances fuel use across the following 24 hours, the session-level split matters even less than it looks.
What the trials found
Keating's meta-analysis of 28 studies compared interval training with moderate continuous training and found no significant difference in total body fat change. Interval work achieved similar results in less time; steady work was gentler and easier to sustain. Neither had a metabolic trick the other lacked.
How to choose your intensity
Pick intensity for the outcome you want beyond fat loss. work builds an aerobic base with low recovery cost and stacks well alongside lifting. Higher-intensity intervals drive VO₂max hardest per minute. Both count toward the ; only your diet decides whether that deficit exists.
Train at the intensity you'll repeat consistently, and set fat loss with total weekly energy — not with a heart-rate band on a treadmill display.