Built with Science founder Jeremy Ethier recently experimented to determine the most effective fat-burning cardio; his findings challenge common fitness assumptions. Using “the world’s most accurate calorie tracker,” Ethier and staff member Dennis Liao tested 12 popular cardio activities, measuring total calories burned, including the proportion from fat versus carbohydrates.
Takeaways
- Fat burn and fat loss aren’t the same.
- Resistance training is more efficient than the “after-burn effect.”
- Prioritize sustainable cardio
The HIIT Afterburn Myth
Ethier started with high-intensity interval training (HIIT) via jumping rope. In 10 minutes, he burned 146 calories; Liao burned 69. Despite HIIT’s reputation for burning more calories after exercise, also known as post-exercise oxygen consumption (EPOC), the post-exercise calorie burn was modest — only 28 extra calories for Ethier and eight for Liao.
However, their session wasn’t true HIIT. “True high intensity…heart rate should reach at least 85%,” asserted Ethier. Their next activity was sprints.
Do Sprints Burn the Most Calories?
“Some researchers claim one minute of all-out effort can offer the same benefits as 50 minutes of normal cardio,” Ethier noted. (1) Sprints are considered the pinnacle of calorie-burning activities because they produce the highest calorie-burning rate — in Ethier’s case, 17.8 calories per minute — but 97% of those calories came from carbs, not fat. That’s not bad, though, since the body switches to fat burning for fuel.
EPOC was smaller than expected for the activities tested. Ethier affirmed that resistance training is more beneficial than HIIT for the supposed EPOC benefits. (2)
Jogging, Fasting & Fat Burn vs. Fat Loss
Jogging for 20 minutes burned 350 calories for Ethier, keeping his heart rate consistently elevated. He also tested jogging while fasted.
Fat burn and fat loss are different…the amount of fat loss achieved depends upon net calorie surplus or deficit.
—Dr. Eric Helms
Some research confirms an insignificant long-term fat loss advantage to fasted cardio. (3)
Banded Races and Swimming
Swimming has been proven to burn calories but with minimal joint stress, unlike jogging, which involves repetitive joint impact. High-level swimmers burn up to 6,000 calories daily. (4) Ethier burned 276 calories in 20 minutes of swimming, including the thermogenic effect from water cooling.
Walking: The Fat-Burning Surprise
Walking at 3.2 mph for 30 minutes burned almost 200 calories each for Ethier and Liao — 80% from fat — the highest of any exercise tested. However, total calories burned are more critical.
Incline walking increased calorie burn by 50%. Adding a 20-pound backpack boosted Liao’s burn by 30%. Ethier compared losing body fat to “taking off a backpack” — as your body weight decreases, daily calorie expenditure drops, which suggests why fat loss often stalls without proper adaptations while losing weight. Every additional 1,000 calories burned reduces the risk of death by 12 percent. (5)
Stairmaster & Skill Building
Stair climbing yielded 256 calories in 20 minutes for Ethier, making it a high-burn, joint-friendly option. Boxing burned slightly more (270 calories). Skill training or enjoyable hobbies are more likely to lead to long-term adherence.
Final Verdict
“Exercises you could maintain a relatively high heart rate for a long time…consistently burn the most calories,” Ethier explained. Examples include swimming, stair climbing, and jogging.
The optimal cardio strategy is choosing something you can consistently stick to long-term. Ethier favors walking; Liao prefers swimming. Combining cardio with resistance training and a proper diet will likely yield the best results.
“The best combination is doing a bit of cardio, focusing on your diet, and lifting weights for your muscles and metabolism,” Ethier concluded.
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References
- Gillen JB, Martin BJ, MacInnis MJ, Skelly LE, Tarnopolsky MA, Gibala MJ. Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment. PLoS One. 2016 Apr 26;11(4):e0154075. doi: 10.1371/journal.pone.0154075. PMID: 27115137; PMCID: PMC4846072.
- Tucker WJ, Angadi SS, Gaesser GA. Excess Postexercise Oxygen Consumption After High-Intensity and Sprint Interval Exercise, and Continuous Steady-State Exercise. J Strength Cond Res. 2016 Nov;30(11):3090-3097. doi: 10.1519/JSC.0000000000001399. PMID: 26950358.
- Schoenfeld BJ, Aragon AA, Wilborn CD, Krieger JW, Sonmez GT. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr. 2014 Nov 18;11(1):54. doi: 10.1186/s12970-014-0054-7. PMID: 25429252; PMCID: PMC4242477.
- Sagayama H, Mimura K, Toguchi M, Yasukata J, Tanaka H, Higaki Y. Total energy expenditure in elite open-water swimmers. Appl Physiol Nutr Metab. 2019 Feb;44(2):225-227. doi: 10.1139/apnm-2018-0450. Epub 2018 Aug 28. PMID: 30153424.
- Paluch AE, Bajpai S, Bassett DR, Carnethon MR, Ekelund U, Evenson KR, Galuska DA, Jefferis BJ, Kraus WE, Lee IM, Matthews CE, Omura JD, Patel AV, Pieper CF, Rees-Punia E, Dallmeier D, Klenk J, Whincup PH, Dooley EE, Harris TB, Hooker SP, Shiroma EJ, Yates T, Stamatakis E, Troiano RP, Lavie CJ, Lavie CJ, Fulton JE. Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts. Lancet Public Health. 2022 Mar;7(3):e219-e228. doi: 10.1016/S2468-2667(21)00302-9. PMID: 35247373; PMCID: PMC8910464.
Featured image: @jeremyethier on Instagram
