I lost 220 pounds over fifteen years, and people always want the protocol. What cardio. How much. High intensity or long and slow. They want the trick. So let me give you the answer the research actually supports, which is less exciting than the one you were hoping for and far more useful.
For fat loss, both work, and the difference between them is small. When you match the total work, high-intensity interval training and moderate steady-state cardio produce broadly comparable reductions in body fat across the meta-analyses (BMC Sports Science, Medicine and Rehabilitation, 2025; multiple systematic reviews on PubMed Central). HIIT's genuine advantage is time — similar results in less of it — not some hidden metabolic magic.
The magic is what gets oversold. You've heard about the "afterburn," the calories you keep spending after a hard session. It's real. It's also small — on the order of six to fifteen percent on top of the workout, with HIIT near the top of that range (Cleveland Clinic). A four-hundred-calorie session might add sixty. Across a week, the afterburn is a tip, not the bill. Anyone selling you intervals as a way to eat the same and melt fat through residual burn is selling you a rounding error dressed up as a strategy.
And the other myth worth killing: that HIIT keeps people more consistent because it's more fun. The long-term data doesn't back it. A review of trials running twelve months or more found no superior adherence for HIIT over steady continuous exercise (Journal of Science and Medicine in Sport). Dropout rates are similar. The enjoyment is individual.
The dominant variable in fat loss is sustained energy balance — what you eat and whether you keep moving, repeated long enough to compound. The cardio you choose matters far less than whether you'll still be doing it in six months. If you're fit, time-crunched, and injury-free, HIIT is efficient. If you're a beginner, carrying extra weight, or protecting joints, steady-state is lower risk and easier to recover from — which means you'll do more of it.
That's the whole thing. Not the protocol. The repetition. I didn't lose the weight because I found the perfect workout. I lost it because I stopped chasing the perfect workout and built one I could repeat on the days I didn't feel like it. Pick the one you'll keep. Then keep it.
Sources: BMC Sports Science, Medicine and Rehabilitation (2025) HIIT vs MICT meta-analysis; systematic reviews via PubMed Central; Journal of Science and Medicine in Sport on long-term adherence; Cleveland Clinic on EPOC. Educational only — talk to a physician before starting a new training program.
George Leith is the founder of Evolved Pros and author of EVOLVED, available for pre-order at evolvedpros.com/book.
