What Are Maintenance Calories?
Maintenance calories (also called Total Daily Energy Expenditure or TDEE) represent the number of calories your body needs each day to maintain its current weight. At this caloric intake, the energy you consume from food equals the energy your body expends through basal metabolism, physical activity, and the thermic effect of food.
Understanding your maintenance calories is the foundation for any weight management strategy. To lose weight, you eat below maintenance (a caloric deficit). To gain weight, you eat above maintenance (a caloric surplus).
The Mifflin-St Jeor Equation
Published in 1990, the Mifflin-St Jeor equation is the most widely recommended formula for estimating Basal Metabolic Rate (BMR). The American Dietetic Association considers it the most accurate for most individuals.
Maintenance calories are then calculated by multiplying BMR by the Physical Activity Level (PAL) factor:
Physical Activity Levels (PAL)
| PAL Category | Factor | Description | Example |
|---|---|---|---|
| Sedentary | 1.2 | Little or no physical activity | Office worker, no exercise |
| Light Activity | 1.4 | Light daily activity or recreation | Walking, light housework, casual sports 1-2x/wk |
| Moderate Activity | 1.6 | Regular moderate exercise | Jogging, cycling, gym 3-5x/wk |
| Hard Activity | 1.75 | Vigorous daily exercise | Construction worker, daily intense training |
| Very Hard Activity | 2.0 | Very intense exercise or physical labor | Military training, heavy manual labor + exercise |
| Athlete | 2.4 | Elite competitive athlete | Olympic-level training, professional endurance sports |
Energy Balance Diagram
Factors Affecting Caloric Needs
- Age: BMR decreases approximately 1-2% per decade after age 20, primarily due to loss of lean muscle mass.
- Sex: Males generally have higher caloric needs due to greater muscle mass and larger body size.
- Body composition: Muscle tissue is more metabolically active than fat tissue. Two people at the same weight but different body fat levels will have different BMRs.
- Genetics: Individual metabolic rates can vary by up to 200-300 kcal/day even among people of similar size and activity level.
- Thermic Effect of Food (TEF): Protein has the highest TEF (20-30%), meaning your body uses more energy to digest protein than carbs (5-10%) or fat (0-3%).
- NEAT (Non-Exercise Activity Thermogenesis): Fidgeting, walking around the house, and other non-exercise movements can account for 200-900 kcal/day.
- Hormones: Thyroid function, cortisol, and other hormones can significantly impact metabolic rate.
How to Adjust Your Calories
Calculator estimates are starting points, not precise measurements. Here is how to refine your calorie target:
- Start eating at the calculated maintenance level for 2-3 weeks
- Weigh yourself daily at the same time (morning, after using the bathroom) and track the weekly average
- If your weight stays stable, you have found your true maintenance
- If you are losing weight, increase by 100-200 kcal; if gaining, decrease by 100-200 kcal
- Repeat until your weekly average weight is stable
Worked Example
A 30-year-old male, 70 kg, 170 cm, moderately active (PAL 1.6):
To lose 0.5 kg per week: 2,588 − 500 = 2,088 kcal/day
To gain 0.5 kg per week: 2,588 + 500 = 3,088 kcal/day
Frequently Asked Questions
How accurate are online calorie calculators?
Online calculators estimate maintenance calories within about 10-15% of actual values for most people. The Mifflin-St Jeor equation is the most accurate widely-used formula, but individual variation means you should treat the result as a starting point and adjust based on your body's response over 2-3 weeks.
Why does BMR decrease with age?
The primary reason is sarcopenia — the gradual loss of muscle mass that occurs with aging. Since muscle is metabolically active tissue, less muscle means a lower BMR. This decline can be partially offset by resistance training to maintain muscle mass.
Should I eat back exercise calories?
If you selected an activity level that already accounts for your exercise, you do not need to eat back additional calories. If you selected "Sedentary" and exercise on top of that, you may want to add 50-75% of estimated exercise calories (fitness trackers tend to overestimate).
What is the minimum safe calorie intake?
General guidelines suggest not going below 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. Very low calorie diets (below 800 kcal) should only be done under medical supervision as they carry risks of nutrient deficiencies, muscle loss, and metabolic adaptation.