Question
(a) How long can you play tennis on the 800 kJ (about 200 kcal) of energy in a candy bar? (b) Does this seem like a long time? Discuss why exercise is necessary but may not be sufficient to cause a person to lose weight.

a) $30.3 \textrm{ min}$

b) Yes, this is surprisingly long. A lot of exercise is needed to burn more energy than what is consumed, although exercise also causes the amount of energy burned while at rest to also increase. Exercise increases the resting metabolic rate, in other words.

Solution Video