This article is from the Diet FAQ, by Claudia McCreary cookignnewsletter@chef.net with numerous contributions by others.
For processed foods, check the nutrition information panel on the package,
which should indicate how many grams of fat one serving contains; each gram
of fat contributes about 9 calories towards the total number of calories per
serving. For example, one serving of crackers might break down as follows:
60 calories, 1 gram of protein, 10 grams of carbohydrate, and 2 grams of
fat. In order to determine what percentage of the calories in this food come
from fat, multiply the weight of the fat (in grams) by 9, then divide this
figure by the total number of calories in a serving. In our example, 18
calories (2 g fat * 9 cal/g), or 30% of the total calories (18 cal/60 cal =
0.30), come from fat. The remaining calories come from the protein and
carbohydrate, which each provide only about 4 calories per gram. (If the
weight of a serving of food is more than the combined weight of its fat,
protein, and carbohydrate weights, the "missing" weight is probably due
mostly to water, which has no calories.)
NOTE: Take a closer look at those food products that proudly proclaim that
they're "85% fat-free!". Such statements can be misleading, since they
usually mean that the productis 15% fat by weight, not that the product gets
only 15% of its calories from fat. (Gram for gram, fat contains more than
twice as many calories as protein and carbohydrates.) For example, a serving
of a brand-name turkey breakfast sausage which is allegedly "85% fat-free"
has 6 grams of fat in each 80-calorie serving, and therefore gets more than
67% (6 * 9/80 = 0.675) of its calories from fat.
You may wish to purchase an inexpensive book on nutrition information to
look up foods which are not labeled with nutrition information. (Or, try the
Nutrition Analysis Tool at http://www.ag.uiuc.edu/~food-lab/nat/. It works
best with browsers capable of displaying tables.) Fruits, vegetables,
berries, grains, legumes (peas and beans), and egg whites generally have
little fat. (Avocados, olives, nuts, soybeans, and seeds--such as sunflower
seeds, and even seeds from low-fat vegetables such as pumpkins--are
exceptions.) Any food which looks oily or leaves greasy stains on a paper
napkin is probably high in fat. This doesn't mean that you should never eat
high-fat foods, only that you should balance them with lower fat foods such
as grains, vegetables, and fruits. Keep the broad picture in mind; evaluate
your diet over a period of a day (or a couple of days) and aim to keep your
total fat intake under 30% at most (10-20% if possible).
 
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