Memory tricks for Macronutrients

Essential amino acids can't be synthesized by the body and must be obtained through diet. PVT TIM HALL covers the 9 truly essential aminos (Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Leucine, Lysine) plus Arginine, which is conditionally essential — required during growth, illness, or stress even though adults can normally produce enough on their own.

Carbohydrates and protein each provide 4 kcal per gram. Fat provides more than double that at 9 kcal per gram — which is exactly why high-fat foods pack so many calories into small portions. Alcohol isn't a true macronutrient but still supplies 7 kcal per gram, more than carbs or protein but less than fat.

Simple carbohydrates are mono- or disaccharides (glucose, fructose, sucrose) — quick to digest, quick energy spike. Complex carbohydrates are polysaccharides (starch, fiber) made of long glucose chains that take longer to break down, producing a slower, steadier rise in blood sugar. This is the structural reason whole grains are recommended over refined sugar.

Soluble fiber dissolves in water to form a gel, slowing digestion — this helps lower LDL cholesterol and blunts blood sugar spikes. Found in oats, beans, and apples. Insoluble fiber does not dissolve; it adds bulk to stool and speeds material through the intestines, preventing constipation. Found in wheat bran, whole grains, and vegetable skins.

A complete protein contains all 9 essential amino acids in adequate amounts — meat, eggs, dairy, soy, and quinoa all qualify. An incomplete protein is missing one or more essential aminos — most plant proteins fall here (rice is low in lysine, beans are low in methionine). Complementary proteins pair two incomplete sources whose missing aminos cover for each other — rice + beans together forms a complete amino acid profile.

Saturated fatty acids have no double bonds — their carbon chains pack tightly together in a straight line, making them solid at room temperature (butter, lard, coconut oil) and associated with raised LDL cholesterol. Unsaturated fatty acids have one or more double bonds, creating a kink in the chain that prevents tight packing — making them liquid at room temperature (olive oil, canola oil) and generally considered heart-healthy.

Trans fats form when liquid vegetable oil is artificially hydrogenated to make it more solid and shelf-stable (think old-style margarine and packaged baked goods). Unlike natural saturated fat, which only raises LDL, trans fat both raises LDL ("bad" cholesterol) and lowers HDL ("good" cholesterol) — a double hit that makes it the single most harmful fat type, which is why many countries have restricted or banned it.

Omega-3 fatty acids (found in fatty fish, flaxseed, walnuts) are generally anti-inflammatory and support heart and brain health. Omega-6 fatty acids (found in vegetable oils like corn and soybean oil) are also essential but promote inflammation when consumed in excess relative to omega-3. The typical Western diet runs 15:1 or higher omega-6 to omega-3, far above the roughly 4:1 ratio considered healthier.

LDL carries cholesterol from the liver to tissues and can deposit it in artery walls, contributing to plaque buildup — remember it as "Lousy." HDL carries excess cholesterol back to the liver for disposal, effectively cleaning it out of the bloodstream — remember it as "Healthy." Dietary cholesterol has less impact on blood cholesterol than saturated and trans fat intake does, a common exam misconception.

The glycemic index ranks carbohydrate-containing foods by how quickly they raise blood glucose relative to pure glucose (GI 100). High-GI foods (white bread, white rice, sugary cereal) cause a rapid spike and crash. Low-GI foods (lentils, most vegetables, whole oats) release glucose slowly, producing steadier energy and blood sugar — a key concept in diabetes management and diet planning.

The AMDR gives a healthy range rather than one fixed number, since needs vary by person and goal. Carbohydrates should make up 45-65% of total daily calories, protein 10-35%, and fat 20-35%. These ranges overlap on purpose — a diet can shift toward more protein and less carb (or vice versa) and still fall within healthy bounds, as long as none of the three drops out of range entirely.

Unlike carbohydrates and fat, which the body readily burns for energy, protein's primary role is structural and functional: building and repairing muscle and tissue, forming enzymes and antibodies, and serving as the backbone for many hormones. The body will only break down protein for energy when carbohydrate and fat stores are depleted (such as in starvation or very-low-carb states) — a state called gluconeogenesis, which is metabolically costly and not the body's preferred fuel source.