Fats

Core Concepts

What a fat molecule looks like

Dietary fats are mostly triglycerides: one glycerol "backbone" with three fatty acids attached, like a three-pronged holder holding three candles. A fatty acid is a chain of carbons with hydrogens attached; the chain's shape determines how the fat behaves:

• Saturated fatty acids have no double bonds — straight chains that pack tightly and are solid at room temperature (butter, lard, coconut oil).
• Monounsaturated fatty acids have one double bond, putting a kink in the chain (olive oil, canola oil, avocado, most nuts).
• Polyunsaturated fatty acids have two or more double bonds and are even more fluid (vegetable oils, fatty fish, walnuts, flaxseed).

The kinks from double bonds keep unsaturated fats liquid — pure chemistry that explains why olive oil pours and butter doesn't.

Saturated, unsaturated, and trans fats

• Saturated fats dominate in animal foods (meat fat, butter, cheese, cream) and some plant oils (coconut, palm). High intake is associated with higher LDL cholesterol and cardiovascular risk in population studies, which is why guidance often suggests limiting them.
• Unsaturated fats — the fats in olive oil, nuts, seeds, avocados, and fish — are what most dietary patterns encourage.
• Trans fats are created by partial hydrogenation, which adds hydrogen and straightens chains, turning liquid oil into semi-solid spread. Industrially produced trans fats are strongly associated with higher cardiovascular risk, and many countries restrict them. "Partially hydrogenated oil" on a label is a red flag worth teaching patients to spot.

Essential fatty acids and cholesterol

Two fatty acids are essential: linoleic acid (omega-6, in vegetable oils, nuts, seeds) and alpha-linolenic acid (omega-3, in flaxseed, walnuts, canola oil). The body uses them to build signaling molecules and membranes. Longer-chain omega-3s (EPA, DHA) come mainly from fatty fish and are sometimes called conditionally essential because conversion from alpha-linolenic acid is limited.

Cholesterol is a different lipid — not a fatty acid and not essential in the diet, because the liver makes all the body needs. It is a membrane component and precursor of steroid hormones and vitamin D. In blood, cholesterol travels inside lipoproteins: LDL (low-density) delivers cholesterol to tissues; HDL (high-density) is involved in returning it. These are blood particles, not foods. Current dietary guidance has shifted focus from food cholesterol toward the types of fat eaten, but recommendations continue to evolve — nurses should teach the general concept and defer specific targets to the care team.

Digestion and absorption: the lymph detour

Fat digestion is slow and needs help. Lingual and gastric lipases start the work, but the main action is in the small intestine: bile (made in the liver, stored in the gallbladder) emulsifies fat into tiny droplets, and pancreatic lipase breaks triglycerides into fatty acids and monoglycerides. Intestinal cells reassemble them into triglycerides and package them into chylomicrons — lipoproteins that travel through the lymphatic system before entering the blood. This detour is why fat absorption is slower than carbohydrate absorption, and why disrupted bile or pancreatic function can cause fatty stools and fat-soluble vitamin deficiency.

Fat storage

Beyond meals, the body stores excess energy as fat in adipose tissue, which cushions organs, insulates, and releases fatty acids as fuel between meals. Body fat is also hormonally active; nurses discuss weight with person-first language and without assumptions about habits.

Common Confusions