How Many Calories Do You Need?
Your Total Daily Energy Expenditure (TDEE) — the number of calories your body burns each day — has four components: Basal Metabolic Rate (BMR), the Thermic Effect of Food (TEF), Non-Exercise Activity Thermogenesis (NEAT), and Exercise Activity Thermogenesis (EAT).
BMR (60–75% of TDEE): calories burned at complete rest keeping organs functioning. TEF (8–10%): calories burned digesting food. NEAT (15–30%): unconscious movement — fidgeting, standing, walking — highly variable between individuals. EAT (variable): intentional exercise.
The most evidence-supported BMR equation is Mifflin-St Jeor (1990): Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. Multiply by activity factor (1.2–1.9) to estimate TDEE.
Calorie Targets for Weight Loss
One pound of fat equals approximately 3,500 calories. To lose 1 lb/week, create a daily deficit of 500 calories. To lose 2 lbs/week, create a 1,000 calorie/day deficit. However, 2 lbs/week is generally the maximum recommended for sustainable loss without excessive muscle loss.
A crucial caveat: the '3,500 calories = 1 lb' rule overestimates long-term weight loss because of metabolic adaptation. As you lose weight, BMR decreases (you're a smaller person) and NEAT often unconsciously decreases (your body conserves energy). A 500-calorie daily deficit doesn't produce exactly 52 lbs of loss in a year — it produces more like 25–35 lbs in practice.
For sustained fat loss, most sports dietitians recommend: never eat below 1,200 calories/day (women) or 1,500 calories/day (men), prioritize protein (0.8–1g per lb of body weight), include structured diet breaks (maintenance calories for 1–2 weeks every 6–8 weeks), and use progressive resistance training to preserve muscle mass during the deficit.
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Protein, Carbs, and Fat: How to Split Your Calories
Once you know your calorie target, the macro split determines your body composition outcome. Protein (4 cal/g): the most important macro for body composition. High protein preserves muscle during a deficit and has the highest satiety of all macros. Target: 0.7–1.0g per pound of body weight. For a 170 lb person: 119–170g protein/day.
For fat loss, a common split is 30% protein, 35% carbohydrate, 35% fat. At 1,800 calories: 135g protein, 158g carbs, 70g fat. For muscle gain, shift toward carbohydrates: 25% protein, 50% carbs, 25% fat — carbs fuel training and muscle glycogen.
The protein thermic effect means 20–30% of protein calories are burned in digestion — effectively making high-protein eating a mild calorie-burning strategy. Replacing 200 calories of carbohydrates with 200 calories of protein burns an extra 30–50 calories/day through TEF alone.