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  • With Mayo Clinic nutritionist

    Katherine Zeratsky, R.D., L.D.

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Question

Body fat: What happens to lost fat?

When you lose weight, where does the lost body fat go?

Answer

from Katherine Zeratsky, R.D., L.D.

To understand the answer, it helps to remember that fat is basically stored energy. Your body converts fat to usable energy for your muscles and other tissues through a series of complex metabolic processes. This causes your fat cells to shrink.

These metabolic activities also generate heat, which helps maintain your body temperature, and waste products. These waste products — water and carbon dioxide — are excreted in your urine and sweat or exhaled from your lungs.

Next question
Slow metabolism: Is it to blame for weight gain?
References
  1. Cell metabolism. In: Stanfield CL, et al. Principles of Human Physiology. 4th ed. San Francisco, Calif.: Benjamin Cummings; 2010:88.
  2. Fundamentals of human energy transfer. In: Katch VL, et al. Essentials of Exercise Physiology. 4th ed. Baltimore, Md.: Lippincott Williams & Wilkins; 2010:175.
  3. The endocrine system: Regulation of energy metabolism and growth. In: Stanfield CL, et al. Principles of Human Physiology. 4th ed. San Francisco, Calif.: Benjamin Cummings; 2010:607.
AN01327 April 28, 2012

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