Fats Lipids

About Fats Lipids

Dietary fats provide 9 calories per gram, making them the most energy dense macronutrient, and are needed to absorb vitamins A, D, E and K, build cell membranes and make hormones. Dietary guidelines set an acceptable range for the share of energy from fat. Saturated fats have no double bonds and are common in butter and coconut oil, monounsaturated fats have one and abound in olive oil and avocados, and polyunsaturated fats have two or more and occur in fish and vegetable oils. Industrial trans fats from partial hydrogenation raise LDL and lower HDL cholesterol, and a United States ban on partially hydrogenated oils took effect in 2018. Saturated fat raises LDL cholesterol, though effects differ by chain length, with stearic acid largely neutral. The diet heart hypothesis, linked to Ancel Keys and the Seven Countries Study, remains debated. Replacing saturated fat with polyunsaturated fat rather than refined carbohydrate lowers cardiovascular risk, and the PREDIMED trial found a Mediterranean diet rich in olive oil or nuts reduced cardiovascular events.