Why is a combination of diet and physical activity best for maintaining ideal levels of body fat?

Combinding both of them is important when you are trying to remain healthy. They both play a big factor in the process, because if you are doing all the right amounts of physical activity but not eating right them that activity isn't going to be very helpful, and if you are eating in the best way possible but not getting that physical activity in then that isn't going to show much either when it comes down to the process of maintaing an ideal level of body fat. In order to maintain the ideal amount you need to balance the both of these things out so that they can work together properly.

Explanation:

are there any letter choices to this or is this an open ended question?

answer; (d) braking faster then cars;