How Many Calories Should You Eat to Lose Weight?

Most people who count calories never calculate their actual target — they guess. Here is the precise method doctors and registered dietitians use.

A caloric deficit is the only mechanism by which body fat is lost. There is no exception, no workaround, no supplement that bypasses this principle — it is thermodynamics, and the research is unambiguous. What varies is how much you need to eat to create that deficit, and how to do it without triggering the metabolic adaptation that causes most diets to fail. The Mifflin-St Jeor equation, published in 1990 and validated against indirect calorimetry in multiple populations, is the most accurate formula for estimating Basal Metabolic Rate (BMR) — the calories your body needs at complete rest.

For women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161. For men the constant is +5 instead of −161. The result is multiplied by an activity factor: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, and 1.9 for extremely active.

The final number is your Total Daily Energy Expenditure (TDEE) — your maintenance intake. To lose weight, you eat below TDEE. A 500-calorie daily deficit produces approximately one pound of fat loss per week, since a pound of body fat contains roughly 3,500 calories. A 1,000-calorie daily deficit produces two pounds per week, though this threshold is where most people encounter problems.

Research published in the American Journal of Clinical Nutrition found that caloric intake below 1,200 calories per day consistently produced nutrient deficiencies in adult women, regardless of body size. The body also responds to aggressive restriction by suppressing thyroid output and reducing Non-Exercise Activity Thermogenesis (NEAT) — the unconscious movement throughout the day — in an effort to defend its current weight. Protein intake is the single most important variable during caloric restriction. When you eat in a deficit, your body will source amino acids from existing muscle tissue if dietary protein is insufficient.

A 2014 meta-analysis in the British Journal of Nutrition found that higher protein intake (above 1 gram per kilogram of bodyweight) preserved lean mass during energy restriction. Some research suggests that active individuals benefit from even higher targets — up to 1.6 grams per kilogram — though results vary by training status and age. The practical approach: calculate your TDEE, subtract 500 calories, aim for at least 0.7 grams of protein per pound of bodyweight daily, and adjust after four weeks when your weight adjusts your BMR downward. Progress is not linear — recalculate every 10 to 15 pounds lost to keep the deficit accurate.