Sports Nutrition

The three macronutrients are protein, carbohydrates, and fats. Each provides energy: protein and carbs yield ~4 kcal/g, while fat yields ~9 kcal/g.

Most sports nutrition guidelines recommend 1.2–2.0 g of protein per kg of body weight per day for athletes, depending on the sport and training intensity. Endurance athletes need ~1.2–1.4 g/kg; strength athletes need ~1.6–2.0 g/kg.

Carbohydrates are the body's preferred fuel source during moderate-to-high intensity exercise. They are stored as glycogen in muscles and liver, providing readily available energy for athletic performance.

Glycogen is the stored form of glucose found in muscles (~300–400 g) and the liver (~75–100 g). It is the primary fuel for exercise above ~65% VO2max and its depletion leads to fatigue and reduced performance.

Simple carbs (monosaccharides, disaccharides) are quickly digested and raise blood sugar rapidly (e.g., fruit, sugar, honey). Complex carbs (polysaccharides) digest more slowly and provide sustained energy (e.g., oats, rice, potatoes).

Endurance athletes typically need 6–10 g of carbohydrate per kg of body weight per day, depending on training volume and intensity. During ultra-endurance events, needs may exceed 10 g/kg/day.

Dietary fat provides essential fatty acids, supports hormone production (including testosterone), aids absorption of fat-soluble vitamins (A, D, E, K), and serves as a fuel source during low-intensity and prolonged exercise.

Athletes should consume 20–35% of total daily calories from fat. Intake below 20% can impair hormone production and fat-soluble vitamin absorption. Emphasis should be on unsaturated fats.

Omega-3s (EPA and DHA) are essential polyunsaturated fatty acids found in fatty fish, flaxseed, and walnuts. They reduce inflammation, support cardiovascular health, may improve recovery, and have been linked to reduced exercise-induced muscle soreness.

Saturated fats have no double bonds between carbon atoms (solid at room temperature, e.g., butter). Unsaturated fats have one or more double bonds (liquid at room temperature, e.g., olive oil). Unsaturated fats are generally considered healthier.

Biological value measures the proportion of absorbed protein that is retained and used by the body. Whole egg has a BV of 100 (reference), whey protein ~104, casein ~77, and soy ~74.

A complete protein contains all nine essential amino acids in adequate amounts: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Examples include meat, fish, eggs, dairy, soy, and quinoa.