Nutrition and Weight Management
Energy math
Protein and carbohydrate yield about 4 kcal per gram, fat about 9, and alcohol about 7. Total daily energy expenditure is basal metabolic rate (roughly 60-75 percent of the total), the thermic effect of food (about 10 percent), and activity. A deficit of roughly 500 kcal per day approximates 1 lb of fat loss per week, though the 3,500-kcal rule overestimates long-term loss because expenditure falls as body mass drops.
Macronutrient targets
Active adults commonly need 1.2-2.0 g of protein per kilogram daily, up to about 2.2 g/kg for hypertrophy-focused training. Carbohydrate scales with training volume, roughly 3-5 g/kg for general activity up to 8-12 g/kg for heavy endurance loads. Fat generally supplies 20-35 percent of calories. For hydration, replace roughly 1.25-1.5 L of fluid per kilogram of body mass lost during exercise.
Weight management
Safe loss runs about 0.5-1 percent of body weight per week; lean gain about 0.25-0.5 percent per week. Spot reduction does not occur. Body-composition methods each carry error - treat skinfolds and bioelectrical impedance as trend tools rather than truth.
Supplements and red flags
Creatine monohydrate (3-5 g per day) and caffeine (3-6 mg/kg) have the strongest evidence base. Screen for disordered eating, the female athlete triad, and relative energy deficiency in sport, and never recommend banned or unproven substances.
Traps
Questions swap the kcal-per-gram values, confuse grams per pound with grams per kilogram, or imply that a supplement is required for results.
Rule of thumb: build the calorie target from estimated TDEE, adjust by 300-500 kcal, set protein first, fat second, and fill the remainder with carbohydrate.