Lipids are an essential component of a balanced human diet. Triglycerides, which make up the majority of dietary lipids, are found in both saturated fats—commonly present in meat, dairy products, and certain tropical plants like coconut, and hydrogenated oils such as margarine and baking shortenings (trans fats)—and unsaturated fats, which are abundant in seeds, nuts, olive oil, and most vegetable oils. The main sources of cholesterol include egg yolks, various meats and organ meats, shellfish, and dairy items. Interestingly, regardless of dietary consumption, about 85% of blood cholesterol is generated by the liver. The liver has the ability to convert one type of fatty acid to another, but cannot produce linoleic acid, a component of lecithin. This is why, as an omega-6 fatty acid, linoleic acid is considered essential and must be included in our diet. Linolenic acid, an omega-3 fatty acid, is also deemed essential. Luckily, both linoleic and linolenic acids are present in most vegetable oils. Despite their ambiguities, particularly among those struggling with weight issues, fats are beneficial to the body for several reasons. Besides giving food a tender, flaky, or creamy texture and promoting satiety, fats also serve as a protective buffer around organs, a skin insulator, and a convenient, concentrated energy store. They are key components of myelin sheaths, cellular membranes, and plasma membranes. Cholesterol, another crucial element, helps stabilize plasma membranes and serves as the starting material for the synthesis of bile salts, steroid hormones, and other essential molecules. However, cholesterol is not used for energy. Prostaglandins, regulatory substances derived from linoleic acid through arachidonic acid, contribute to smooth muscle contraction, blood pressure regulation, and inflammation. Triglycerides fuel the energy demands of skeletal muscles and liver cells. Additionally, fats are vital in the absorption of fat-soluble vitamins. Despite fats constituting over 40% of the calories, focusing on healthier fats, like plant oils, and limiting saturated and trans fats supports better health. It is suggested that fats should make up 30% or less of total calorie intake, with saturated fats limited to 10% or less of total fat intake, and daily cholesterol intake not exceeding 300 mg (equivalent to 1½ egg yolks). These guidelines aim to keep total blood cholesterol under 200 mg/dl given the association between high serum cholesterol (especially LDL cholesterol) and cardiovascular disease.

Overconsumption of saturated and trans fats or high blood cholesterol leads to obesity and increases the risk of cardiovascular diseases like atherosclerosis. On the other hand, not consuming enough fats leads to weight loss, problems with heat loss, eczema-like skin lesions, and depression.