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    Slide 2 puts the optimal fat burning range at 80% and cites Journal of Sports Sciences. Seems too high.

  2. ckimp says:

    Hi Erin, so if I wanted to get stronger and lose fat I should also do LSD 3+ times/week with my lifting program. Should I do these runs on the same day and right after my lifts?

  3. Lacey says:

    My main goal right now is to lose fat (without losing muscle), with that said what would you recommend cardio wise? I lift anywhere from 3-5 days a week, depending on my schedule, but my cardio is all over the place. I would like to develop a cardio schedule (length and type) that would best suite my goals, any suggestions?

  4. Heather Sims says:

    LOVED this article! Really having a hard time trying to balance it all. My main goal is to burn fat (I’m 5’5 and 120), but I want to maintain my muscle, and I love all types of workouts. But due to the plethora of internet information, I’m trying to do so much: Yoga, Pilates, Kickboxing, Low Intensity Cardio, High Intensity Cardio, Lifting, Metabolic Resistance, Plyo, and all in a week?! Yikes!! I really do enjoy it, but I’m having such a hard time organizing it all, which makes it more of a chore rather than a positive experience. Would love to hear your thoughts/advice.

  5. Chris says:

    Hello, just read this and found it to be the best that the web had to offer – in other words – it was solid! Thanks for compiling and I appreciated your summaries as well. My question is this – how do you recommend I practically obtain my fat burning zone? I’m not sure if your 60% – 80% above is based on the Karvonen formula or other (i.e.220 minus age or other method)? I know the Karvonen formula tends to calculate higher than most. I just got a heart rate monitor from Polar and the 60% – 80% rates they recommend based on my age, height and weight seem too low especially in comparison to the much higher rates that the Karvonen formula gives. Any guidance would be greatly appreciated. Thanks so much!!

    • Hi Chris! Glad you liked my article! As far as the formulas, I’m honestly not sure what is the best way to estimate your rates, since these papers were doing actual laboratory tests to determine those ranges. I looked up some commonly used formulas, and would probably recommend the results from Robergs and Landwehr (2002), who studied 43 different formulas and came up with HRmax = 205.8 − (0.685 × age). Getting your max with this formula would give you a number to calculate your 60-80% range. You could also use the Karvonen formula to get straight to the range. Obviously, these are all approximations, so to truly know your HRmax, you’d have to get hooked up to an ECG and do a treadmill test. Some gyms offer a version of this test (I know Lifetime Fitness does), so you may want to check into that if you want to get a better estimate for yourself! Good luck!

    • Randall says:

      Are you using the simplified Karvonen where target HR is calculated by finding a percentage of HRmax where HRmax equals 220 – age? Or by calculating a percentage of HR reserve and adding resting heart rate to find the target heart rate?

  6. Philipp says:


  7. […] the kind of cardio that I do. And while I have posted before about the fat burning benefits of low intensity cardio, there are also lots of benefits to high intensity cardio as well. These cardio workouts are […]

  8. […] This stance is backed by science, as I’ve outlined in my article: The Science of Burning Fat (https://erinsimmonsfitness.wordpress.com/2012/01/20/science-of-burning-fat/). I’m not sayin HIIT won’t burn the fat, it certainly will, but low intensity cardio burns the […]

  9. Joe says:

    So basically, for optimal fat burning the ‘traditional’ jogging is just fine, right? 50pct of VOmax — you could achieve that with an easy jog.

    What I’m wondering is where/what the motivation for HIIT stuff came from?

    Seems like alot of bodybuilders don’t enjoy ‘traditional’ cardio and so HIIT is seen as a quick short and more “exciting” version of cardio.

    What do you think?

    • Yes, jogging will do it! HIIT will burn a lot of calories, and in the process burn fat. The thing about low intensity is that it more specifically targets fat loss, whereas HIIT breaks down muscle as well. I’m sure the motivation for it came from not wanting to do long workouts and people would rather sacrifice some muscle breakdown to burn a lot of calories quick. I think bodybuilders especially should be conscious of this, since it is counterproductive to break down muscle. I believe everything should be in balance, personally. But in order to specifically target fat loss, low intensity long workouts are scientifically shown to be the way to go.

  10. Audrina jacob says:

    You definitely keep me motivated at the gym! I’m kinda stuck at the moment because it seems like when I go to the gym I do the same stuff. My overall goal is to tone my muscle but I haven’t really found a decent workout that I see results with! So I’m wondering if you could help me with that? And is there a good diet to go on I know some can cause health issues if they lack nutritional value.

    • Did you look at some of the different workouts I’ve posted? Those should give you some different ideas of things to do. As far as diet, I don’t recommend any certain diet (“fad” diets), just a balanced, healthy diet that meets nutritional requirements and reduces overly processed, unnatural foods. See the Mayo Clinic Pyramids that I posted. Also, check out my sample meal plan.

  11. Andy Johnson says:

    Great article, Erin. My approach has been to do 30 minutes of LISS in the morning (3.5mph walk at 4% incline) and weightlifting after work. I’d love to see you do a future article about whether “body recomposition” is actually possible. Most of what I’ve read indicates that the body is either cutting or bulking, depending on caloric intake, but it’s almost impossible to cut fat and build muscle simultaneously. On my workout plan, I THINK I’m seeing results in terms of fat loss, but the scale isn’t moving at all. (I’m doing bodyfat comp. tests every 2 months or so to check, but I’m about 3 weeks away from the next one and getting antsy). If there’s some hard evidence that recomposition either IS or ISN’T possible, I would change up the regimen accordingly.

    • Andy, I think what you should take from this article is that it is definitely possible to cut fat and build muscle at the same time! I have never personally seen anything to the contrary. What have you read that says you can’t? If you are doing low intensity cardio, then you won’t be burning through muscle for energy, you’ll be targeting fat. Then if you mix that with weightlifting (and I would also suggest proper supplementation of some sort of protein before and after your workout to combat the breaking down of muscle and helping it rebuild) then you are building muscle at the same time. I can try to find studies that have specifically looked at this, but like I said, if you build muscle then even when you’re not working out it will be burning calories that your body will take from fat as long as you are keeping isocaloric (not taking in more calories than you’re burning). Athletes build muscle while keeping body fat low all the time! But I’ll look and see what I can find.

  12. Jim says:

    If I haven’t had a VO2max test but have access to a heart monitoring device, what would be the optimal heart rate for a low intensity 5k (or 30 min) run to burn the most fat?

    • Hi Jim! Thanks so much for asking that question, I meant to include that part but forgot! The way we do get VO2max here is called the Balke Method (check out http://www.brianmac.co.uk/balketread.htm for detailed instructions). Basically, you start on the treadmill at a lower speed, bring it to a slightly higher speed after a minute, and then every two minutes after that you increase the incline of the treadmill (we use 2.5% every 2 minutes, but as the website says, you can do less than that). If you have a polar monitor or watch, you can do this test to monitor your heart rate during the test and get your maximum heart rate.

      Basically you can do this test as it’s described on this website and instead of monitoring your VO2max, monitor your heart rate. When you get to the end of the test, which means you reach ultimate fatigue where you can not go anymore (but preferable without flying off the treadmill!), then stop. This would be easiest with a polar monitor that you can then plug into your computer and see your heart rate throughout the test. Obviously, the highest value will be your maximal heart rate.

      Note: The website I gave you has a VO2max calculator, but I don’t like it. For instance, when I tested here at work, I ran for over 12 minutes if I remember correctly and had a VO2 max of 50 (this was using a mask that actually measures your oxygen intake and carbon dioxide output). This calculator says mine would only be 21! So I’m not sure how that’s calculating it, so I would just use your heart rate. Especially since you can’t monitor your VO2 max on any sort of instrument during normal training.

      • Jim Shaki says:

        I know cyclist that sleep with their heart monitors on at night and measure their resting heart rate first thing in the morning. Once I establish my resting and maximum what would be the optimal “fat burning zone” based on the research above? I’m guessing around 70%… is that correct?

        • Jim, the articles don’t mention anything about resting HR, though it would be good to know your range. But based on these articles, 60-80% of your maximum HR would be the fat burning zone! So yes, aiming for the middle of that zone around 70% would likely give you the best results.

  13. ksmahoney says:

    While it’s true that the body derives a higher percentage of energy from fat at lower intensities, none of these studies cite total calories burned. At higher intensities, you may have a lower percentage fat burned, but a large number of total calories. If you walk briskly for 30 minutes and burn 200 calories, 50% of those may be from fat (100 calories). However, if you ran hard for an hour and burned 800 calories, while the percent from fat is lower (perhaps 25-30), you would still burned a larger amount of calories from fat (200-250).
    Sara from http://www.losingtogether.com

    • True, however, the point is that if you were to do a lower intensity walk or run for a longer period of time, you are still burning a large number of calories that come from a greater percentage of fat. Your comparison doesn’t hold because you aren’t comparing equal amounts of time. If you were to just run hard for 30 minutes while burning a very low percentage of fat (and from these studies, that percentage is likely less than the 30% you say here) then you may only be burning 60-80 calories as opposed to walking for the same amount of time and burning 100 fat calories. See? You have to compare them over the same time intervals.

  14. Jed says:

    I go to the gym daily, and I alternate days of weight lifting with short jogs (usually 15-20 minutes), and days of long runs (45 minutes to an hour). Does this sound like a good way to burn fat?

    • Absolutely! Just keep in mind that it is probably your longer runs (assuming your longer runs are lower intensity, like mine are) that will be burning more fat, so if that’s your goal, you may want to have 3 days of those long runs and adjust the rest of your schedule accordingly.

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