The human body burns calories every second — breathing, circulating blood, maintaining body temperature, digesting food, and moving. Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a day. Eat above your TDEE and you gain weight. Eat below it and you lose weight. No diet approach — keto, intermittent fasting, paleo — changes this fundamental equation.
The Four Components of TDEE
- •Basal Metabolic Rate (BMR): ~60–70% of TDEE. Calories burned at complete rest — to keep organs functioning, maintain body temperature, and sustain life. This is largely determined by age, sex, height, and weight.
- •Thermic Effect of Food (TEF): ~10% of TDEE. The energy used to digest and metabolize food. Protein has the highest TEF (20–35%); fat has the lowest (0–3%).
- •Non-Exercise Activity Thermogenesis (NEAT): ~15–20% of TDEE. Calories burned through everyday movement — walking, fidgeting, doing chores, typing. This varies dramatically between people.
- •Exercise Activity: 0–30% depending on your training volume. Structured workouts — running, lifting, cycling.
Calculate Your Daily Calorie Target
Setting a Calorie Deficit for Fat Loss
One pound of body fat contains approximately 3,500 calories. A 500-calorie daily deficit produces roughly 1 pound of fat loss per week — the commonly recommended rate. Aggressive deficits (1,000+ calories/day) cause faster weight loss but also increase muscle loss, hunger, metabolic adaptation, and diet adherence problems.
- •Mild deficit (–250 cal/day): 0.5 lb/week loss. Sustainable, minimal muscle loss. Best for people close to goal weight.
- •Moderate deficit (–500 cal/day): ~1 lb/week. The standard recommendation. Works for most people.
- •Aggressive deficit (–750–1,000 cal/day): 1.5–2 lb/week. Can work short-term but increases risk of muscle loss and metabolic slowdown.
- •Never go below BMR: Going too low signals starvation and causes your body to aggressively preserve fat and burn muscle.
The scale is noisy. Water retention, glycogen storage, and hormonal fluctuations can mask real fat loss. Track your average weight over 2-week periods rather than day-to-day changes to see the real trend.
Why TDEE Calculators Are Estimates
TDEE calculators use population-average formulas (Mifflin-St Jeor is the most accurate) that predict your metabolic rate. Individual variation can be ±15–20%. Some people burn 200 calories more per day than the formula predicts; others burn 200 less. This is why calorie calculators work for most people but not everyone — and why tracking actual results over 3–4 weeks and adjusting is more reliable than trusting any formula perfectly.
Macronutrients: Where the Calories Come From
- •Protein: 4 cal/gram. 0.7–1g per pound of body weight is the research-supported range for muscle preservation and satiety. Higher protein intake makes dieting significantly easier.
- •Carbohydrates: 4 cal/gram. Primary fuel for the brain and high-intensity exercise. Not inherently bad — excess is the problem.
- •Fat: 9 cal/gram. Essential for hormone production, cell function, and fat-soluble vitamin absorption. Do not go below ~0.3g per pound of body weight.
- •Fiber: 25–35g/day supports gut health, slows digestion, and dramatically improves satiety per calorie.
Frequently Asked Questions
How many calories should I eat to lose weight?
A safe deficit is 500–750 calories/day below your TDEE (Total Daily Energy Expenditure), which produces roughly 1–1.5 lbs of fat loss per week. Never go below 1,200 calories (women) or 1,500 calories (men) without medical supervision — aggressive restriction triggers muscle loss and metabolic adaptation.
Calculate your TDEE →What is TDEE and how is it calculated?
TDEE is your Total Daily Energy Expenditure — all the calories your body burns in 24 hours including resting metabolism, daily movement, exercise, and food digestion. It equals BMR (basal metabolic rate) × activity multiplier. A sedentary 35-year-old woman at 150 lbs might have a TDEE around 1,750; a very active man of the same stats, 2,800+.
Find your TDEE →Is 1,200 calories enough to eat every day?
For most adults, 1,200 calories is too low as a sustained diet. While it can work short-term for small, sedentary women, it typically causes muscle loss, nutrient deficiencies, extreme hunger, and metabolic slowdown for everyone else. Most health organizations recommend deficits no deeper than 500–750 cal/day from TDEE.
How many calories are in one pound of fat?
One pound of body fat contains approximately 3,500 calories. That means a sustained deficit of 500 calories/day should produce roughly 1 pound of fat loss per week. In practice, weight loss also depends on water retention, muscle changes, and hormonal factors — the relationship is not perfectly linear.
Does the timing of when I eat calories matter?
Total calories over the day matter far more than timing for most people. That said, front-loading calories earlier in the day, eating protein at every meal, and not skipping breakfast can help manage hunger and reduce overeating at night. Intermittent fasting works for some people because it naturally creates a calorie deficit — not because of any metabolic timing magic.