Dear Confused fat burner,

Whenever we exercise, we are burning both fat and carbohydrate. We also burn more energy (calories) at higher levels of intensity. So, when our heart rate is higher, we are using a higher percentage of carbohydrate (as glycogen, the storage form of carbohydrate found in muscles); and, since we are using more energy overall, we will use more fat, too. Regarding your question, what this means is that we will be burning a larger number of fat calories at a higher intensity, given an equal amount of time. In other words, in thirty minutes, we will burn more fat calories at 160 beats per minute than at 125 (assuming you are able to keep your heart rate at 160 for thirty minutes).

As we become more aerobically trained, our bodies adapt and rely on burning a higher percentage and total number of fat calories all the time. This spares glycogen so that our muscles don't tire out easily during exercise. Another benefit of exercise is the development of muscle tissue. The more lean body mass we have (which is often a result of exercising), the more calories we burn all day (and all night too!).

Also consider is energy balance. To burn fat and lower body fat, the calories we eat cannot exceed the calories we expend, because if they do, they will be stored as fat. If this is the case, you will be adding, not losing, fat.

To burn as much fat as possible in a set amount of time, work at a challenging intensity you can comfortably manage for the entire duration. An easy measure is being able to talk, but not sing, while exercising. For most people who exercise regularly, this is about 70 to 75 percent of maximum heart rate (MHR) -- see below for information on how to calculate this number. As your fitness level improves, you may be able to increase exercise intensity and/or duration and your fat burning abilities.

Use the following formula:

Maximum Heart Rate (MHR), calculated by subtracting your age from 220, is an accepted indicator of exercise intensity. For example, MHR for a twenty year old is: 220 - 20 = 200. His/her range should be 65 to 85 percent of MHR. For a twenty-year-old person, this is 130 (65 percent of 200) to 170 (85 percent) beats per minute.

Alice

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