In other words, you may lose fewer pounds than if you expended the same number of calories on an aerobic activity like brisk walking or swimming, but you will be stronger and better toned. With greater muscle mass, your basic metabolic rate will rise and you will burn more calories all day and night. And since muscle holds less water and takes up less room than the equivalent weight of fat, by shedding fat and gaining muscle you can lose inches and sizes without losing actual pounds on the scale.

Keep in mind, though, that the time spent doing resistance exercise burns fewer calories than if the same time were spent on aerobic activities.

Mr. La Forge pointed out that how skilled you are at your chosen activity also influences the calories burned. Those less skilled make unnecessary movements or have to work harder at the activity, using more calories an hour than those who perform it efficiently. That may sound like it is an advantage to be unskilled, but there is a significant downside: Those with less skill tend to tire faster and thus spend less time at the activity. They are also more prone to overuse injuries.

Another factor in caloric burn is the increased number of calories the body uses after a workout. Both aerobic and resistance exercises raise energy expenditure over the next 12 to 24 hours, but the range is great — from 10 to 150 calories, depending on the type of activity and how long and vigorously it was done. Though it does not sound like much, it can add up over the long run.

Your Body Counts, Too

People who are overweight or obese burn more calories proportionately doing the same activity, for the same duration and at the same intensity, than those of normal weight.

But some people compensate for the calories burned by eating more or doing less. If you exhaust yourself by overexercising, you may do less routine activity for the rest of the day, reducing the caloric benefit of your workout.

Or if you know you expended 300 extra calories in your morning workout, you may — consciously or otherwise — make up for them by eating more that day. On the other hand, many people find that a vigorous workout before lunch or dinner diminishes their appetite and reduces their overall caloric intake, adding to the weight loss resulting from the exercise itself.