Concerning personal finances there is an old saying:
If your outgo exceeds your income, your upkeep will be your downfall.

In weight loss the opposite is true:
If the incoming calories exceed the outgoing calories, this will be your downfall. Weight loss will not occur.

The incoming calories derive from one source only, from what we consume, from what we eat or drink.

The outgoing calories, on the other hand, the calories we expend, can be looked at as being used up via two different modes.

The first mode is the heightened expenditure of calories through exercise. A rodeo rider making eight (staying up on a Brahma bull or a bucking bronco for eight seconds) is using up a lot of energy, a lot of calories with this exercise.

A couch potato, in contrast, uses up fewer calories making eight, unless the "eight" is in reference to "eight hours". Nevertheless, the couch potato does burn up calories just lying there. In fact, even when we are at complete rest we all burn up calories at a lower rate called the basal metabolic rate.

For some people, this basal metabolic rate is higher, and more calories are used up while they are at rest. For others it is lower, and fewer calories are used up while they are at rest. For people in a given age group, these differences in basal metabolic rate can manifest themselves in obvious ways.

For instance, those with the lower metabolic rate are the ones that can, seemingly, just walk by a breadbox and put on a pound or two. Those in the other group - the ones with the higher metabolic rate - can swallow an entire bakery and remain lean.