Quit debating! To burn more fat, work harder or longer—or both.Weight management programs abound, and they employ countless strategies and approaches. But all these programs should include three principal components: (1) an exercise plan that incorporates cardiovascular and resistance training to increase caloric expenditure and maintain muscle mass; (2) a lifestyle/ dietary approach that emphasizes balanced nutrition and decreased caloric intake; and (3) a behavior modification strategy to support implementation of the exercise and lifestyle components. With fitness industry professionals, perhaps the one topic—or obsession— that will surely generate debate in the exercise component of the plan is, What is the best exercise fat-burning zone? This article will attempt to bring clarity where there is cloudiness, research where there is perception, and guidance where there is dissent on this contestable issue and related matters.
When a person has a negative energy balance, weight loss may come from three body sources: water, adipose tissue (fat) and muscle tissue. Under most circumstances, body water will remain relatively normal as long as regular hydration is maintained. The goal of a weight loss plan is to lose fat while preserving muscle mass.
To further substantiate this association, I conducted a simple experiment. A 191-pound physically fit male student performed 30 minutes of treadmill exercise under two conditions: (1) at 55% of his heart rate maximum (HRmax) and (2) at 85% of his HRmax. The results of this experiment were as follows:
At the higher intensity, the subject burned more total calories, more fat calories and more carbohydrate calories. But not every client can exercise the way this very fit student can. For people who are sedentary or at orthopedic, cardiac or health risk, high-intensity exercise may be contraindicated. For their weight loss exercise plans, low- to moderate-intensity exercise should be performed for progressively longer durations. In fact, since most people can't do high-intensity exercise on a daily basis, owing to potential overtraining and overuse concerns, perhaps the best strategy is to integrate and balance the low- to moderate-intensity, long-duration workouts with high-intensity workouts for optimal fat-calorie burning.
1. An improved oxygen delivery and extraction system (via blood flow and capillarization) helps cells burn fat more efficiently.
2. The sensitivity of muscle and fat cells to epinephrine is enhanced, leading to improved release of fatty acids (which are the disassembled triglycerides) into the blood and within the muscle (where fat is in its triglyceride storage form).
3. An augmented circulatory blood flow system aids in the delivery of fatty acids to the muscle.
4. The amount of fatty acids allowed to enter the muscle increases, making more fat available for fuel.
5. An improvement in the specialized protein transporters that admit the fatty acids into the muscle cells makes the fat more readily available.
6. The mitochondria, sometimes referred to as the cells' "fat-burning furnaces," increase meaningfully in number and size.
7. The oxidative enzymes that speed up the breakdown of fatty-acid molecules to be used during aerobic exercise increase. An important take-home message for all your students and clients is that consistent, progressively challenging cardiovascular exercise will truly develop their bodies into much better fat burners.
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Hill, A.J. 2004. Does dieting make you fat? British Journal of Nutrition, 92 (Suppl. 1), S15-18.
Horowitz, J., & Klein, S. 2000. Lipid metabolism during endurance exercise. American Journal of Clinical Nutrition, 72 (2, Suppl.), 558S-63S.
Thompson, D.L., et al. 1998. Substrate use during and following moderate- and low-intensity exercise: Implications for weight control. European Journal of Applied Physiology and Occupational Physiology, 78 (1), 43-49.
© 2007 by IDEA Health & Fitness Inc. All rights reserved. Reproduction without permission is strictly prohibited.
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