Nutrition, Weight Management, and Body Composition
Core concepts
Understand energy balance, macronutrient roles, and safe weight management. Know that carbohydrate and fat are primary fuel sources, protein supports repair and maintenance, and hydration supports performance and thermoregulation. Grasp body composition assessment methods (skinfolds, bioelectrical impedance, hydrostatic weighing, DXA) and their assumptions and error sources. Understand basal metabolic rate, thermic effect of food, and physical activity energy expenditure as components of total daily energy expenditure. Know the energy content of macronutrients: carbohydrate and protein about 4 kcal/g, fat about 9 kcal/g, and alcohol about 7 kcal/g. Recognize signs of disordered eating and refer appropriately.
Traps in questions
A frequent trap is advising extreme calorie restriction or rapid weight loss. Safe rates are typically modest, and very low intakes risk lean mass loss and nutrient deficiency. Questions may confuse body composition methods or overstate their accuracy. Another trap is recommending protein or supplements without evidence. Watch for hydration misconceptions, such as relying on thirst alone during long or hot exercise. Also avoid equating weight loss with fat loss.
Worked example
A food provides 50 g carbohydrate, 20 g protein, and 10 g fat. Energy = (50 × 4) + (20 × 4) + (10 × 9) = 200 + 80 + 90 = 370 kcal.
Rule of thumb
Use the 4-4-9 rule for macronutrient energy and recommend gradual, sustainable changes rather than extreme restriction.