Most people refer to this group of nutrients as “fats,” however the appropriate name is “lipids.” They are a family of organic substances that are mostly insoluble in water, meaning they do not mix well with water.  Fats are considered a macronutrient because they’re measured in grams; we typically consume 70 to 100 grams each day.  Because they provide 9 kcal per gram instead of 4 kcal like carbohydrates, some people consider them “fattening.” In reality, we need to consume a certain amount of fats to survive.

Recall from Chapter 2 that the first four items listed on Nutrition Facts labels are lipids: total fat, saturated fat, trans fat and cholesterol. They are listed first because they are considered “nutrients of concern” and should be limited in our diets. Countless years of studies have shown that reducing the intake of these lipids reduces risk of heart disease.

This chapter introduces the three classes of lipids: triglycerides (fats and oils), sterols (cholesterol), and phospholipids.  After looking at the structures, sources, and functions of lipids, we’ll discuss how the body handles them with health implications of diets high in certain types of lipids.