How Many Calories to Lose Weight? TDEE and Safe Deficits

To lose weight, you need to eat fewer calories than your body burns. A common starting point is to estimate your total daily energy expenditure (TDEE) and eat about 500 calories a day less, which US health guidelines link to a loss of roughly 1 to 2 pounds a week at the start.

Weight loss does not stay linear, though. As you lose weight, your body burns less, so the same calorie target produces slower progress over time. This guide shows how to estimate your numbers, what counts as a safe deficit, and what NIH research says about realistic rates. It is general information, not medical advice. If you have a health condition, are pregnant, or take medication, speak to a doctor or dietitian before changing your diet.

Step 1: Estimate your resting needs (BMR)

Your basal metabolic rate (BMR) is the energy your body uses at rest. The Mifflin–St Jeor equation (Mifflin et al., 1990) is widely used. A 2005 systematic review found it the most reliable of the common prediction equations for healthy adults with and without obesity, though individual results can still be off by 10% or more.

Example: a 35-year-old woman, 165 cm tall, weighing 80 kg.

Step 2: Multiply by your activity level (TDEE)

TDEE adds the energy you use moving, working and exercising. Calculators multiply BMR by an activity factor. These multipliers are commonly used:

Most people overestimate their activity. If you are unsure, pick the lower level. The TDEE calculator works this out for you.

As a sanity check, the Dietary Guidelines for Americans 2020–2025 (Appendix 2) estimate that women aged 31 to 50 need about 1,800 calories a day if sedentary, 2,000 if moderately active and 2,200 if active. Those estimates are for a reference woman of 5 ft 4 in and 126 lb, so a heavier person needs more.

Step 3: Choose a deficit

Guidelines from US health agencies converge on a moderate deficit:

• The NIH’s National Heart, Lung, and Blood Institute clinical guidelines recommend a diet that creates a deficit of 500 to 1,000 kcal a day to lose 1 to 2 pounds a week.
• The 2013 AHA/ACC/TOS obesity guideline suggests about 1,200–1,500 kcal a day for women and 1,500–1,800 kcal a day for men, or a deficit of 500 or 750 kcal a day, adjusted for body weight.
• The CDC notes that people who lose about 1 to 2 pounds a week are more likely to keep the weight off.

For the woman in our example, moderately active at 2,318 kcal, a 500 kcal deficit means eating about 1,818 kcal a day. That sits above the 1,200–1,500 range, which is fine: the guideline ranges are typical targets, not minimums to aim for.

Why not a much bigger deficit?

Very low intakes make it harder to get enough protein, vitamins and minerals, and they are harder to stick to. Very-low-calorie diets are used in medicine, but under supervision. If a calculator suggests eating below about 1,200 kcal a day, talk to a health professional first.

Why the 3,500-calorie rule overpromises

You may have heard that a pound of fat holds about 3,500 calories, so a 500-calorie daily deficit loses 1 pound every week, forever. By that rule, our example would lose 500 × 365 ÷ 3,500 = 52 pounds (23.7 kg) in a year.

Real bodies do not work that way. As you lose weight, you burn fewer calories: a smaller body needs less energy to run and to move, and metabolism adapts. So a fixed calorie intake produces a shrinking deficit.

Researchers at the NIH quantified this. Kevin Hall and colleagues built a mathematical model of human metabolism, published in The Lancet in 2011, which now powers the NIDDK’s free Body Weight Planner. For an average adult with overweight, their rule of thumb is:

Applied to a sustained 500 kcal (2,092 kJ) a day cut, that suggests an eventual loss of roughly 21 kg (about 46 lb), with about half, roughly 10 kg (23 lb), in the first year. That is a solid result, but less than half of what the 3,500-calorie rule predicts for the same year.

Other studies agree. A 2013 analysis in the International Journal of Obesity compared the 3,500-calorie rule with tightly controlled weight-loss studies and found that it overpredicted weight loss, while dynamic models like Hall’s matched the results much better.

These are population averages. Your result will depend on your starting weight, body composition, activity and how closely you track intake.

Put it together: a realistic plan

1. Estimate TDEE with the TDEE calculator, choosing a conservative activity level.
2. Subtract 500 kcal (or up to 750 if your TDEE is high). The calorie deficit calculator gives a daily target and projected timeline.
3. Track for 2–3 weeks, weighing yourself under the same conditions. Day-to-day weight swings by a kilogram or more because of water and food, so watch the weekly average.
4. Expect a slowdown after the first months. That is physiology, not failure. Recalculate TDEE at your new weight and decide whether to adjust intake or activity.
5. Plan for maintenance. Keeping weight off means eating at your new, lower TDEE, which is less than before. Physical activity helps.

To set a goal weight, it helps to know your healthy weight range. Our guide to BMI shows how to calculate it, and the BMI calculator does it instantly.

Quality matters as well as quantity

Calorie targets are easier to hit with foods that fill you up for fewer calories: vegetables, fruit, legumes, whole grains, and protein foods such as fish, eggs, dairy, beans and lean meat. Sugary drinks and highly processed snacks add calories without much fullness. Protein and strength training help preserve muscle while you lose fat.

FAQ

How many calories should I eat to lose 1 pound a week?

Roughly 500 fewer than your TDEE, according to NIH clinical guidelines. Expect the weekly loss to slow over time as your body needs less energy.

Is 1,200 calories a day enough?

It is the lower end of the range the 2013 guideline suggests for women, and some people need much more. Diets below about 1,200 kcal a day are generally used only under medical supervision.

Why did my weight loss stop?

As you lose weight, your TDEE falls, so your deficit shrinks. Water shifts can also hide fat loss for a week or two. Recalculate your needs at your current weight.

Is the 3,500 calories per pound rule wrong?

It is a fair estimate of the energy in a pound of body tissue, but it ignores that your energy needs fall as you lose weight. Used as a long-term forecast, it overestimates weight loss.

What is the most accurate way to plan weight loss?

Dynamic models such as the NIH Body Weight Planner account for metabolic changes over time, so they predict more realistic timelines than simple calorie arithmetic.