How to Use Your TDEE for Weight Loss

TDEE for weight loss means eating below your TDEE by a set amount. Start 500 to 750 kcal under it, and never go below 1,200 kcal a day for women or 1,500 kcal for men. The AHA/ACC/TOS guideline allows those deficits and lists those intakes as typical. The NHS suggests aiming to lose 0.5 to 1 kg (1 to 2 lb) a week.

How do I find my TDEE for weight loss?

Your TDEE, or total daily energy expenditure, is the calories you burn in a day, so it’s the level where your weight holds. Estimate it with an equation, then treat the result as a starting point. NASEM’s 2023 equations use age, height, weight and one of four activity levels. Their typical error is about 246 kcal for women and 339 kcal for men. For an everyday average to compare with, see how many calories per day adults need, which starts from the NHS guide of 2,000 kcal for women and 2,500 for men.

Pick the activity level from your whole week. NASEM’s low active level means daily living plus 60 to 80 minutes of walking. If you sit most of the day, inactive is the honest row. I’ve caught myself picking one row too high more than once, and it always showed up as a stalled scale.

Person	Activity	TDEE (kcal/day)
Woman, 35, 165 cm, 70 kg	low active	2,269
Woman, 50, 155 cm, 55 kg	inactive	1,765
Man, 40, 178 cm, 85 kg	low active	2,896

Each TDEE above comes from the NASEM adult equations, worked row by row. These three people are my examples from here on.

How big should the deficit be?

A deficit of 500 kcal a day is the usual starting point. The AHA/ACC/TOS guideline also lists 750. Hall and colleagues describe the old rule of 3,500 kcal per pound. By that rule, 500 kcal a day is about 0.45 kg (1 lb) a week. A 750 kcal deficit gives 0.68 kg (1.5 lb), and 250 kcal gives 0.23 kg (0.5 lb).

Daily deficit	Weekly loss by the 3,500 kcal rule (kg)	Weekly loss (lb)
250 kcal	0.23	0.5
500 kcal	0.45	1.0
750 kcal	0.68	1.5

Treat it as a rough start. The next section shows how it drifts. Your target is TDEE minus the deficit, provided the answer stays above the floor. How many calories should I eat to lose weight runs the same sum from maintenance calories.

The woman at 2,269 kcal lands on 1,769 kcal with a 500 kcal deficit, and the man at 2,896 kcal lands on 2,396 kcal (typical totals for men are in how many calories a man should eat a day). The smaller woman is the interesting case. Her TDEE is 1,765 kcal, so 500 kcal off leaves 1,265 kcal, only 65 kcal above the 1,200 kcal floor. A 750 kcal deficit would put her at 1,015, so the floor decides. Her largest usable deficit is 565 kcal, or about 0.5 kg (1.1 lb) a week. The same guideline reserves diets under 800 kcal a day for medical settings, where trained practitioners supervise them.

Everything here assumes a BMI above the usual range of 18.5 to 24.9, which is who these deficit sizes are meant for. BMI can’t tell muscle from fat. If you lift, or you’re unsure where you stand, the NHS suggests looking at waist size too, and a doctor can help. If your BMI is already in the usual range, a calorie deficit isn’t a plan I’d write for you.

Why does the deficit shrink as I lose weight?

Because a smaller body burns less. The 3,500 kcal rule assumes your TDEE stays put, and Hall’s team call it wrong for that reason. Take their 100 kg sedentary man who cuts 480 kcal a day. He levels off near 75 kg. Half of that loss takes about a year, and 95% of it takes about three. The old rule predicts 22 kg gone in the first year, about twice what the model shows.

Hall’s model also gives a rule of thumb. A permanent 100 kJ a day of intake change leads to about 1 kg of eventual weight change. That’s roughly 10 kcal a day per pound. So once 10 pounds are gone, your TDEE has dropped by about 100 kcal, and a 500 kcal deficit is closer to 400. The same arithmetic runs upward, and how many calories over maintenance to gain a pound covers that side.

I recalculate every 10 pounds (4.5 kg). The loss keeps going, only slower, and nothing has gone wrong when it does.

How do I check my real TDEE after a few weeks?

NASEM’s advice for any estimate is to monitor body weight and adjust intake. Here is how I do that. Log everything you eat for two weeks and weigh yourself most mornings, then use the trend rather than single days. The arithmetic is average daily calories plus 7,700 kcal for each kilogram lost, divided by the days. That 7,700 is the 3,500 kcal per pound rule in metric. I trust it over a few weeks, never over many months.

Say you averaged 2,000 kcal a day and your trend fell 0.6 kg over 14 days of steady eating. That’s 0.6 × 7,700 = 4,620 kcal, or 330 kcal a day. Your TDEE is about 2,330 kcal. No change on the scale? Then your TDEE is about what you ate. Skip logging snacks and the answer comes out too low.

To get your starting number from your age, height, weight and activity, use the calorie calculator. Its equations are the NASEM 2023 ones behind the table above, and it won’t give you a target under 1,200 or 1,500 calories.

Pregnancy, breastfeeding and medical conditions change all of this, and a doctor or midwife sets those numbers.

If counting calories has started to feel hard to stop, or eating feels out of control, talk to someone: ANAD in the US (1-888-375-7767), Beat in England (0808 801 0677), NEDIC in Canada (1-866-633-4220) or the Butterfly Foundation in Australia (1800 33 4673). If you’re in danger right now, call your local emergency number. Other UK numbers and crisis lines are on our crisis support page.