# Fat-burning heart rate **URL:** \ **Category:** Factual Questions\ **Created:** [October 9, 2005, 9:40pm UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445 "2005-10-09T21:40:25Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [October 9, 2005, 9:40pm UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/1 "2005-10-09T21:40:25Z")
After visiting a number of sites that claim to calculate the ideal heart rate for fat burning and getting perplexing results, I turn to the brightest people I know - yes, that’s you guys - instead. The way I understand it, there is a range within which you burn the maximum amount of fat. Above it, you burn more carbohydrates and far above it you pretty much burn only carbohydrates. I am trying to burn as much fat as possible, and currently my cardio regime is a 45-minute session at 140+ beats per minute every other day, finishing off with 6½ minutes of 30-60 interval training. When I step off the bike that feels like pretty much the limit of what I can do right now. Since my resting heart rate is very low - around 45 if measured in the morning when I wake up - most target heart rate calculators give me rates that are way below 140. For example, one calculator says I should stay between 95 and 125. 45 minutes at 125 beats per minute; I could do that standing on my head. Surely there must be more effort to it than that? So, how do I calculate my true target heart rate for maximum fat burning? Am I burning fat with my current cardio regime or wasting time (apart from strengthening my heart, of course)? I am a 28-year-old male, 167 cm tall, weighing around 63-64 kg. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [October 10, 2005, 1:50am UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/2 "2005-10-10T01:50:40Z")
All of the widely available heart rate formulas are for sedentary people. With a resting HR of 45 bpm, that ain’t you. Even if you were sedentary, the formulas wouldn’t really be all that accurate. Your best bet is to get an impedance scale and measure relative changes with that. ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [October 10, 2005, 2:14am UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/3 "2005-10-10T02:14:24Z")
Impedance scales are those that measure body fat percentage, right? I have one of those, but it seems to be wildly inaccurate (unless it’s normal for a 167 cm 63 kg weightlifter to have a body fat percentage swinging wildly between 21% and 26%, which sounds unlikely to me). So there’s no way to find out my optimal heart rate? Should I find a place that performs stress tests, find out my maximum heart rate and ask for help calculating my optimal heart rate? ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [October 10, 2005, 2:23am UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/4 "2005-10-10T02:23:28Z")
> [@Priceguy](#): > > Impedance scales are those that measure body fat percentage, right? I have one of those, but it seems to be wildly inaccurate (unless it’s normal for a 167 cm 63 kg weightlifter to have a body fat percentage swinging wildly between 21% and 26%, which sounds unlikely to me). Are you measuring at the same time of day with similar levels of hydration? > [@](#): > > So there’s no way to find out my optimal heart rate? Should I find a place that performs stress tests, find out my maximum heart rate and ask for help calculating my optimal heart rate? Heart rate is something of a red herring. From Qadgop in [this thread](http://boards.straightdope.com/sdmb/showthread.php?t=338850): > [@](#): > > Heart rate is a rough gauge that is used to measure oxygen consumption during physical exercise. It’s rather inconvenient to measure oxygen consumption directly, unless you have a decent research lab. Thence the suggestion to focus on your body fat levels rather than your heart rate. ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [October 10, 2005, 2:45am UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/5 "2005-10-10T02:45:22Z")
> [@ultrafilter](#): > > Are you measuring at the same time of day with similar levels of hydration? Immediately in the morning when I get out of bed, and immediately after a cardio workout, and in the evening before the last meal of the day (but since my food schedule is rather fluid I do not trust the evening measurements too much since my “time since last meal” will be very different from day to day). The scale was kind of cheap, so I’m afraid I’ve simply got one that doesn’t work properly. Even if we ignore the variations, I have a hard time buying that I’m at 21-26% body fat right now (where was I then before I started training and controlling my diet - 35%?) and that my body fat percentage has barely changed while I’ve dropped three kg and visibly developed muscles. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [October 10, 2005, 2:53am UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/6 "2005-10-10T02:53:23Z")
Not super accurate but most of what I have heard is that sustained exercise past 20 minutes (ie walking, running, aerobics etc) or so usually puts you into the “fat burn” range. [Aerobic Versus Anaerobic Exercise](http://www.well-net.com/cardiov/aerex1.html) > [@](#): > > As you first start to exercise no matter whether you are walking or running, your muscles immediately begin to use energy to allow them to work. For the first three minutes your muscles will burn glycogen, a special sugar which is stored in the muscles for a quick infusion of energy. Some glycogen is always stored within your muscle tissues. During this period fat is not burned. This process is called anaerobic metabolism. Often during the first few minutes of strenuous activity, especially during anaerobic metabolism, you may experience burning in muscles of your arms, legs or back. This is due to the creation of lactic acid which occurs when glycogen is burned. This burning sensation will soon go away. > > As you exercise more than three minutes you will eventually burn up all of the glycogen stored within the muscles and your muscles will move into aerobic metabolism. When this occurs lactic acid production is stopped. This occurs because the glycogen is now being burned in the presence of oxygen which is brought to the muscles by way of the blood stream. As long as you breath correctly you will bring oxygen to the muscles and this process will continue. > Oxygen is essential to the muscle’s ability to function correctly. With adequate oxygen the muscles can extract all the energy they need from blood sugar. During the period you exercise the liver and muscles will release their stored carbohydrate so that it can be used as energy by the muscles hence allowing you to keep on exercising. > Once these stores of glycogen are used up which usually occurs after about 20 minutes, the body will start burning its fat stores to produce blood sugar and ultimately glycogen. The longer you exercise the more fat burned. Fat, body fat and not dietary fat, can now be used virtually indefinitely to produce energy to support your exercise program. > While you are walking, you do not directly burn fat but once you stop walking the glycogen which has been burned up must be replaced. This can only happen by what you eat and by the liver draws fat from the body’s fat tissues. If you are on a limited caloric intake then the food you ingest will be used basically for feeding your brain and fat stores will have to be drawn on to replace the glycogen used up while exercising. > > Studies show that “fat-burning” may last for anywhere from six to twenty-four hours after a regular exercise program. This means that even moderate exercise has long term benefits for you. > > Studies, however, also show us that the percentage of energy contributed from burning fat decreases as you increase the intensity of your exercise program. This means that you do not have to exercise intensely or exert great effort but rather than only mild to moderate exercise on a regular basis is needed. [Exercise Intensity Versus Fat Burning](http://www.seekwellness.com/fitness/fat_max_zone.htm) > [@](#): > > In a recent study conducted in England, at the School of Sport and Exercise at Birmingham University, scientists have identified the Fat Max Zone. Using 25 moderately trained individuals, in both graded and constant exercise programs, researchers have concluded that exercising too intensely will cause fat burning to markedly drop. > > Fat oxidation, or fat burning, is something the human body does quite naturally. Stored body fat, along with the carbohydrates we consume, become our main source of fuel, or energy. Fortunately, the human body is very good at burning fat over a large range of exercise intensities. However, if you train too intensely, sugar will become your main source of energy, not fat. > > So what’s the right intensity to activate all this fat burning? > > Scientists involved in the study used maximal oxygen consumption, or VO2 Max to determine exercise intensity. VO2 Max is a way of expressing how fit you are by gauging how much oxygen your body can use at the cellular level. > > For the best aerobic, or fat burning workout, the traditional, recommended range is from 50 to 85 percent of VO2 Max, when using the heart rate reserve formula found below. This is not to be confused with a simple percentage of your maximum heart rate. > > Researchers involved in this Birmingham study found that the Fat Max Zone (where the most fat was burned) was actually reached at 55 to 72 percent of VO2 Max. This represents a substantially narrower range, especially on the high end (less a whopping 13 percent), than what was previously accepted. Possibly an even more important finding – at levels above 89 percent, fat burning all but ceased. > > THE FAT MAX ZONE > (as measured by the heart rate reserve formula) > > 1. Calculate estimated maximum heart rate (MHR) > using the following formula: > 220 minus age = MHR > Estimated MHR for an average 30 year-old would be: > 220-30 = 190 > > 2. Next, determine resting heart rate (RHR): > Take your pusle for 1 minute white at TOTAL rest: > (Typical RHR = 70) > Subtract RHR from MHR: > 190 - 70 = 120 > > 3. Calculate percentages: > 55% of 120: = 66 > 72% of 120: = 86 > > 4. Add RHR (70) back into to both numbers: > 66 + 70 = 136 > 86 + 70 = 156 > > The Fat Max Zone for an average 30-year-old, would between 136 and 156 beats per minute. Grab a pencil and paper and calculate your own Fat Max Zone. > > Without the need of a trainer, and by using the above formula, you can make sure your aerobic regimen is working towards increasing V02 Max (and your ability to burn fat), while at the same time taking place in the Fat Max Zone. > > Aerobic exercise should be repeated about 3 or 4 times per week, for a period of at least 15 to 20 minutes to achieve optimum results. Be sure to pay attention to how you feel, as well as how you’re breathing, during exercise. > > As a general rule, you shouldn’t feel overly fatigued or winded during aerobic exercise, and you should be able to speak at least three words (or syllables) without taking an in-breath. For more information on aerobic exercise, and how you can burn more fat, pick up a copy of The Firefighter’s Workout Book. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [October 10, 2005, 2:55am UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/7 "2005-10-10T02:55:19Z")
IIRC “fat measuring” weight scales were tested by CR some time ago and were determined to be wildly inaccurate to the point if uselessness. ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [October 10, 2005, 3:00am UTC](https://boards.straightdope.com/t/fat-burning-heart-rate/325445/8 "2005-10-10T03:00:45Z")
**astro** , your second cite is one of the sites I found while searching myself. It puts my Fat Max Zone (which sounds like a trendy if slightly unpleasant night club) between 125 and 183, which is a pretty big range but sounds most credible of the ones I’ve found.