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Metabolism: A Look at the Facts


Metabolism: A Look at the Facts

Metabolism is the amount of energy that you needs per day to keep your body functioning and to complete physical activity. The energy used for these functions comes from the foods that you eat. Your resting metabolic rate (RMR) accounts for 60%-70% of the total calories that you burn by regulating your body temperature, keeping your heart pumping and your organs working, etc.

Some people say that they gain weight easily because they have a “slow metabolism.” Is this true?
Studies show that the difference in metabolism between two people of the same age, gender, height, and body composition is probably less than 3%. If two 35-year-old women who are both 5′7″ and have the same percentage of body fat would both have their metabolism tested, and woman A burned 1600 calories/day, woman B would most likely burn somewhere between 1552-1648 calories/day. Keep in mind that overweight people usually have faster metabolisms than thinner people. This is because the more you weigh, the more your body has to work.

Is it true that exercise increases your metabolism, helping you to burn calories even when at rest?
Even if you increased your muscle mass by 15%, you would only garner a 5% increase in RMR, which would mean that a person who generally eats 2000 calories/day, could eat an extra 75 calories.

Is it true that your metabolism slows down with age?
Yes, this is true. Beginning at age 30 and each decade thereafter, the average person’s metabolism slows down by 2%-3%.

How will dieting affect my metabolism?
Crash dieting can have a very strong impact on your metabolism. After 2 weeks of starvation or semistarvation, RMR is likely to drop by as much as 15%. Once you have cut your daily calorie level to 1000-1200 calories/day, your metabolism will slow down. However, once a person begins to eat a sufficient amount again, metabolism will “bounce back.” Chronic dieters cannot permanently slow down their metabolism, contrary to popular belief.

Is it true that eating more frequently will keep my metabolism running faster and cause me to lose more weight?
Unfortunately, this is not true. Frequency of meals is not correlated to overall metabolic rate. However, this sort of meal plan can keep glucose and insulin levels steady, which may result in less hunger and lead to weight loss.

Does working out increase your metabolism for several hours after you have finished?
If you work out hard enough, it does. Following a high-intensity workout, your body may burn what equates to 15%-20% of the calories that you burned during exercise every hour for a few hours.

Is it true that eating spicy foods will increase my metabolism, helping me to lose weight?
If only it were that easy, we would all be bingeing on chili peppers! Spicy foods do cause a slight increase in metabolism, but the effect is so minimal and short-lived that it does not make a difference as far as weight loss is concerned.

References and recommended readings

Finn C. The myth about muscle and your metabolic rate. Available at: Accessed May 14, 2009.

Funderberg L. Ten truths about metabolism. Available at: Accessed May 14, 2009.

Laquatra I. Nutrition for weight management In: Mahan LK, Escott-Stump S. Krause’s Food, Nutrition, and Diet Therapy. 11th ed. Philadelphia, PA: WB Saunders; 2004:562-563.

Mayo Clinic. Metabolism and weight loss: how you burn calories. Available at: Accessed May 14, 2009. The truth about metabolism. Available at:
. Accessed May 14, 2009.

Uhland V. The burning questions about metabolism. Available at:
. Accessed May 14, 2009.


Review Date 8/09


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