S3( When you jog, most of the food energy you burn above

Chapter 11, Problem 11.74

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S3( When you jog, most of the food energy you burn above your basal metabolic rate (BMR) ends up as internal energy that would raise your body temperature if it were not eliminated. The evaporation of perspiration is the primary mechanism for eliminating this energy. Determine the amount of water you lose to evaporation when running for 30 minutes at a rate that uses 400 keal/h above your BMR. (That amount is often considered to be the maximum fatburning energy output.) The metabolism of 1 gram of fat generates approximately 9.0 kcal of energy' and produces approximately 1 gram of water. (The hydrogen atoms in the fat molecule are transferred to oxygen to form water.) What fraction of your need for w'ater will be provided by fat metabolism? (The latent heat of vaporization of water at room temperature is 2.5 X 10fl J/kg.)