Metabolism is a term that’s widely used — especially in connection with gaining weight or losing it. But what does it really mean?
Put simply, your metabolism refers to all the processes in your body that help you to function normally. This requires energy, which your body gets from the food you eat.
The rate at which your body uses up kilojoules (or energy) to carry out these vital functions is called the metabolic rate. Around five to 10 percent of your energy is used to eat, digest and metabolise food, another 20 percent to burn kilojoules during physical activity (if you are a normally-active person), and the remaining 50–80 percent is the amount of energy used while you are at rest. This is also known as your basal metabolic rate or BMR. The faster your BMR, the more efficiently your body burns up kilojoules.
Your BMR can be influenced by many factors including your body size, age, gender, genetic predisposition, hormones and what you eat. The amount of exercise you do can have an effect as well.
It’s all to do with muscle. Compared to women, men’s bodies generally have more muscle and less fat which makes a difference to your BMR. While fat burns very few kilojoules, muscle is an active, ‘hungry’ tissue that uses up kilojoules even when you’re just sitting around.
Exercise increases the amount of muscle you have—and the more muscle you have, the faster your BMR will be. Although exercise will generally help increase muscle, studies show strength training (also known as resistance training or weight training) builds muscle more effectively and increases BMR.
Other factors that can influence your BMR include:
Better Health Channel: Metabolism explained http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Metabolism_explained.
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Cho S Dietrich M Brown C et al. The Effect of Breakfast Type on Total Daily Energy Intake and Body Mass Index: Results from the Third National Health and Nutrition Examination Survey (NHANES III). Journal of the American College of Nutrition, 2003; 22(4): 296-302.
Dolezal BA Potteiger JA. Concurrent resistance and endurance training influence BMR in non-dieting individuals. Journal of Applied Physiology. 1998; 85: 695-700.
Hensrud D. Slow metabolism: Is it to blame for weight gain? [online] Mayo Foundation for Medical Education and Research. c1998-2010 [last updated 27 Aug 2009, accessed 17 Aug 2010] Available from: http://www.mayoclinic.com/health/slow-metabolism/AN00618.
Last Published: 31 October 2011
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Last published 31 October 2010