The resulting product — which may be blended with other milk products or animal fats (such as lard or tallow) and salt for taste — is margarine. It has been used as a butter substitute since the late 19th century. Sometimes it is referred to as oleomargarine or oleo. Oleo means oil and refers to the vegetable oil base of margarine.
Like butter, regular margarine is about 80 percent fat (actually, law requires this percentage of fat for the product to be labeled margarine) and has the same number of calories. One tablespoon contains about 100 calories and 11 grams of fat.