The taste of my childhood was the taste of skim milk. We spread bright yellow margarine on dinner rolls, ate low-fat microwave oatmeal flavored with apples and cinnamon, put nonfat ranch on our salads. We were only doing what we were told. In 1977, the year before I was born, a Senate committee led by George McGovern published its landmark “Dietary Goals for the United States,” urging Americans to eat less high-fat red meat, eggs and dairy and replace them with more calories from fruits, vegetables and especially carbohydrates.

By 1980 that wisdom was codified. The U.S. Department of Agriculture (USDA) issued its first dietary guidelines, and one of the primary directives was to avoid cholesterol and fat of all …