Peter is a middle-aged, overweight man who is trying to decrease his body circumference. how could the serving size on a nutrition label him lose weight?
it describes how many daily total calories he should eat. he can compare this number to the number of calories he currently consumes.
it allows him to predict how much weight he will lose if he follows the serving size guidelines on the nutrition label.
it describes the portion size of the food that he should eat. this amount can be used as a guideline for preparing food.
it defines how much food he can eat when dining at restaurants and still be able to lose weight.

The correct answer is -  It describes the portion size of the food that he should eat. This amount can be used as a guideline for preparing food.

Peter is probably eating more than the serving/portion size recommends. Once Peter knows what size he should be eating he can then use it as a guideline and will help him figure out what his daily calorie intake will be and should be.  

the more fit you are, the faster the recovery. your heart rate drops most sharply in the first minute after you stop exercising; it should then fall about 20 beats a minute—a drop of less than 12 beats a minute is considered abnormal. this “recovery heart rate” is measured as part of an exercise stress test.