A recent question posted to the Health/Science writer at The Boston Globe has prompted me to cover an often confusing issue regarding burning fat via cardiovascular exercise. Do you burn more fat when exercising at a lower heart rate, and hence lower intensity, versus exercising at a high heart rate/intensity? As Judy Foreman so expertly puts it- NO!
Years ago, fitness instructors and fitness enthusiasts began focusing on low intensity, low heart rate exercise as a”fat burning” regimen. The theory- misinterpreted as it was- was that you can burn MORE fat at lower intensities than at high intensities, thus making low intensity exercise ideal for people trying to reduce body fat. The truth is that what really detemines effective weight loss is the total number of calories burned during exercise. While lower intensities/heart rates burn a greater PERCENTAGE of fat versus other fuels ( stored carbohydrates-sugars), the TOTAL calories expended are much less, and in the long run, you will NOT lose fat more effectively than exercising at higher intensities. IN FACT, we now know that, because higher intensity exercise (70-85% THR) burns more calories per minute, it is quite an efficient way to exercise, as it takes LESS time to burn the same amount of calories as a low intensity workout. Even today, you will see computerized cardiovascular equipment that displays a “fat burning zone” versus “cardiovascular zone” on its LED screen. Don’t be fooled by this marketing technique! It is still optimal to challenge yourself occasionally with more diffucult workouts to produce the best health and weight loss benefits.