How many calories should I eat per day?

What Is BMR and Why Does It Matter?

Your Basal Metabolic Rate (BMR) is the number of calories your body burns every day just to stay alive — breathing, pumping blood, maintaining body temperature, repairing cells, and keeping your organs functioning. BMR accounts for roughly 60–75% of your total daily calorie burn, making it by far the largest component of your energy expenditure.

The most widely validated formula for estimating BMR is the Mifflin-St Jeor equation, published in 1990 and recommended by the Academy of Nutrition and Dietetics as the most accurate predictive equation for healthy individuals. The formulas are:

• Males: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
• Females: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

Your BMR depends primarily on four factors: body weight (more mass requires more energy), height (taller people have more surface area), age (metabolism slows roughly 1–2% per decade after your 20s), and sex (males typically have more lean mass, which burns more calories at rest).

Understanding Activity Levels

Your BMR tells you what your body burns at rest, but you also burn calories through daily movement, exercise, and even digesting food. To estimate your Total Daily Energy Expenditure (TDEE), multiply your BMR by an activity factor:

• Sedentary (1.2): Desk job with little or no exercise. You drive to work, sit at a computer all day, and spend evenings watching TV or reading. This describes the majority of office workers who do not exercise regularly.
• Lightly Active (1.375): Light exercise or sports 1–3 days per week. You might take daily walks, do yoga twice a week, or have a job that involves some standing and light movement.
• Moderately Active (1.55): Moderate exercise 3–5 days per week. You regularly do cardio, weight training, or active sports. This also applies to people with physically active jobs like retail, teaching, or nursing.
• Very Active (1.725): Hard exercise 6–7 days per week. You train intensely most days or have a labor-intensive job like construction, farming, or warehouse work combined with some exercise.
• Extra Active (1.9): Very hard daily exercise, training twice per day, or an extremely physical job. This level is typical for competitive athletes, military personnel in training, or people with demanding physical jobs who also exercise.

Most people overestimate their activity level. If you exercise three times a week but spend the rest of your day sitting, “Lightly Active” is likely more accurate than “Moderately Active.” When in doubt, choose the lower activity level and adjust based on results.

Calorie Deficit for Weight Loss

Weight loss comes down to a fundamental principle: you must burn more calories than you consume. A deficit of approximately 500 calories per day results in about 1 pound of fat loss per week (since one pound of body fat stores roughly 3,500 calories). A 1,000-calorie deficit produces about 2 pounds per week, which is generally considered the maximum safe rate of loss.

For example, if your TDEE is 2,633 calories, eating 2,133 calories per day creates a 500-calorie deficit. Over seven days, that is a 3,500-calorie deficit — approximately one pound of fat. This moderate approach is sustainable and far more likely to produce lasting results than crash dieting.

Why Extreme Calorie Deficits Backfire

It might seem logical that a bigger deficit means faster results, but cutting calories too aggressively (below 1,200 for women or 1,500 for men) often backfires for several reasons:

• Metabolic adaptation: Your body responds to severe restriction by lowering BMR, reducing non-exercise activity (fidgeting, posture maintenance), and increasing hunger hormones. You burn fewer calories and feel hungrier — a recipe for eventual binge eating.
• Muscle loss: With extreme deficits, your body breaks down muscle tissue for energy. Since muscle is metabolically active, losing it further reduces your BMR, making weight maintenance harder long term.
• Nutrient deficiencies: Very low calorie diets make it nearly impossible to get adequate vitamins, minerals, and fiber, which can affect energy, mood, immune function, and bone density.
• Psychological effects: Severe restriction increases food preoccupation, reduces concentration, and often leads to cycles of restriction and overeating.

Macronutrient Balance and Protein

Total calories matter most for weight change, but how you distribute those calories among protein, carbohydrates, and fat affects body composition, satiety, and performance. A widely recommended starting point is:

• Protein: 0.7–1.0 grams per pound of body weight (or 1.6–2.2 g/kg). Protein is especially important during a calorie deficit because it preserves muscle mass, increases satiety, and has a higher thermic effect (your body burns more calories digesting protein than carbs or fat).
• Fat: 20–35% of total calories. Fat supports hormone production, nutrient absorption, and cell health. Do not drop below 20%.
• Carbohydrates: Fill in the remaining calories. Carbs fuel high-intensity exercise and brain function. Whole grains, fruits, and vegetables provide fiber, vitamins, and sustained energy.

When to Recalculate Your Calories

Your calorie needs are not static. Recalculate your TDEE whenever you experience a significant change:

• Every 10–15 pounds of weight change — as your weight drops, your body requires fewer calories to maintain the new weight
• Changes in activity level — starting or stopping an exercise program, changing jobs, or recovering from injury
• Age milestones — BMR naturally declines with age; recalculate annually or when entering a new decade
• If progress stalls for 2–3 weeks — your body may have adapted; reassess intake and activity honestly before reducing calories further

Tracking your weight over time (weekly averages, not daily fluctuations) and adjusting intake by 100–200 calories at a time is far more effective than making drastic changes based on a single weigh-in.