Section 13-1 Nutrients at Work for You 325 Copyright Goodheart-Willcox Co., Inc. Fats Fats are concentrated sources of food energy. They provide slightly more than twice as much energy per unit of weight as carbohydrates and proteins. Fats supply essential fatty acids, which are needed for normal growth. Fats are divided into two classes. Saturated fats are solid at room temperature and are often referred to as solid fats. Unsaturated fats are usually liquid at room temperature and often referred to as oils. Foods from animal sources tend to be higher in saturated fats. Foods from plant sources tend to be higher in unsaturated fats, 13-2. Sometimes manufacturers process unsaturated fats to make them solid. This process is called hydrogenation and the solid fat that is created is called trans fat. Although some are naturally present in food, most trans fats in the diet are man-made. Man-made trans fats are often found in foods such as solid vegetable shortening, microwave popcorn, and frozen pizza. Cholesterol is a fatty substance found in every body cell. The body uses cholesterol to make a number of important materials, including sex hormones and vitamin D. Your body manufactures all the cholesterol you need. However, you also get cholesterol from your diet when you consume foods from animal sources. Saturated fats, trans fats, and dietary cholesterol tend to raise blood cholesterol levels. Excessive cholesterol in the blood can form deposits on the inside of blood vessels. This causes the fl ow of blood to be restricted or blocked completely. A heart attack can result. Therefore, health experts advise people to limit their intake of saturated fats and cholesterol, and avoid man-made trans fats. When the diet is defi cient in fat during infancy and childhood, growth can be stunted. A diet too low in fat can cause skin problems and the C i ht G dh t Will C I 13-2 Sources of unsaturated fats include avocados, fish, and many nuts and seeds.