If you consume excess calories, your body stores them as fat, specifically white adipose tissue. Lately, you may have been hearing about another kind of body fat, called brown fat, which is more metabolically active than white fat.
Butter, margarine and similar spreads shouldn’t form a significant part of your daily diet because they’re concentrated sources of fat and calories. But they also give flavor to food and, when you cook with them, add color and texture.
Until recently, the first prerequisite of a healthy diet was to control your intake of total fat, which supplies about 34 percent of total calories in the average American diet. But smart swaps may be more useful than simply cutting fatty foods.