Fat-free foods may have drawbacks.

Food processors have developed a wide range of fat-free products, ranging from a sour cream-like concoction to modified cheeses, that could help people lose weight and reduce their cholesterol if used carefully and wisely. In the past few years, the varieties of food labeled fat-free have increased substantially, largely because companies have developed recipes that can substitute for fats with natural gums or cellulose, or potentially even more unconventional ingredients, such as pureed prunes. Many truly are fat-free, not simply lower in cholesterol or fat.

"For someone who just has to have cream cheese in his gelatin or sour cream on his baked potato, the fat-free products appear to be a...