Fat grams have more calories per gram than any other calorie source. One gram of fat has nine calories, while one gram of protein or carbohydrates has only four calories. Since it is easy to consume more calories without realizing it, experts recommend limiting the amount of fatty foods in your diet. You can also eat more low-fat foods for the same amount of calories in a food that is heavy in fat. However, there is no difference in calories among the types of fats, such as unsaturated and saturated. For instance, solid fats such as butter and margarine are both equal in calories. To find out the percentage of fat in food, simply multiply the fat gram content by nine. For example, one cup of whole milk contains one hundred and fifty calories and eight grams of fat. Multiply the eight fat grams by nine and you can determine that one cup of whole milk has seventy-two saturated fat calories. The less fat you can consume in packaged foods, the better. For more information on nutrition, contact a health care professional.