Calorie Deficit for Women: Floors, Pace and Protein

A calorie deficit for women is usually 500–600 kcal below maintenance, and the daily intake never goes under 1,200 kcal. For the NHS average of 2,000 kcal, that means 1,400–1,500 kcal. Pace is capped at 1% of body weight a week, and protein sits at 1.2–1.6 g per kilogram. The numbers come from the AHA/ACC/TOS guideline, the NHS and the Dietary Guidelines for Americans.

How big should a calorie deficit be for women?

According to the AHA/ACC/TOS guideline, people in weight-loss programs are typically prescribed a deficit of at least 500 kcal a day. It names 500 kcal, 750 kcal or a 30% cut as options, and it describes 1,200–1,500 kcal a day as the usual target range for women. I use the low end, 1,200 kcal, as a hard floor and never as a goal. For the term itself, see what a calorie deficit is.

The NHS asks for around 600 kcal a day and calls that safe and sustainable. It is 30% of the 2,000 kcal the NHS gives as the daily average for women. The table checks both cuts against the floor.

Your maintenance	After a 500 kcal cut	After the NHS 600 kcal cut	Largest cut that keeps 1,200 kcal
1,600 kcal	1,100 (below the floor)	1,000 (below the floor)	400 kcal
1,800 kcal	1,300	1,200 (at the floor)	600 kcal
2,000 kcal	1,500	1,400	800 kcal
2,200 kcal	1,700	1,600	1,000 kcal

Smaller women reach the floor sooner. At 1,600 kcal of maintenance, the cut that fits is 400 kcal or less, and a 250 kcal cut (1,350 kcal) is a real deficit too. In kilojoules, as on Australian labels, the floor is 5,021 kJ, using 1 kcal = 4.184 kJ.

How many calories should a woman eat to lose weight?

Start from your maintenance, subtract 500–600 kcal and check the result against the table. Maintenance is the number that’s hard to pin down. The NHS gives 2,000 kcal a day as the average for women, and says needs depend on age, weight, height and activity. An older NHS 12-week guide applied the 600 kcal rule and set a 1,400 kcal limit for most women, which is 2,000 minus 600.

Equations miss by a few hundred calories. The NASEM 2023 energy equations have a prediction error of 246 kcal a day for women, so a calculator that says 1,900 kcal is typically off by about 250 in either direction for you. The same report says to plan with the equation, then track body weight over time and adjust.

I do it in three steps:

1. Log your food in grams for 14 days at your usual eating.
2. Compare your average weight in week 1 with week 2. If it’s flat, your average intake is your maintenance.
3. Subtract 250–600 kcal, whichever keeps you at or above 1,200 kcal.

Every later step depends on step 1. Eating less for two weeks from a guessed starting point is how deficits go wrong, and a deficit that isn’t real is why plans stall, as can you lose weight without a calorie deficit shows.

For a first estimate to test, the calorie calculator takes your age, height, weight and activity and applies the NASEM 2023 equations. No target it sets falls under 1,200 kcal for women or 1,500 kcal for men.

How fast should a woman lose weight?

Slowly. The NHS says to aim for 1 to 2 lb, or 0.5 to 1 kg, a week, and a review for lean athletes sets the range at 0.5 to 1% of body weight a week. I treat 1% as the ceiling and never go above 0.9 kg (2 lb), whichever is lower. For women under about 90 kg, that’s the percentage.

Body weight	0.5% a week	1% a week (upper limit)
55 kg (121 lb)	0.28 kg (0.6 lb)	0.55 kg (1.2 lb)
65 kg (143 lb)	0.33 kg (0.7 lb)	0.65 kg (1.4 lb)
75 kg (165 lb)	0.38 kg (0.8 lb)	0.75 kg (1.7 lb)
85 kg (187 lb)	0.43 kg (0.9 lb)	0.85 kg (1.9 lb)

A 55 kg woman who loses 1 kg a week is losing 1.8% of her weight, nearly double the limit. The same review reports that in strength-training women, losing 1 kg a week rather than 0.5 kg over 4 weeks came with a 5% decrease in bench press strength. The slower pace gave up less.

Read the table as the fastest case. Real loss slows as you get lighter, so judge the pace by a two-week average and don’t aim for the top row.

How much protein does a woman need in a deficit?

1.2–1.6 g per kilogram of body weight. That’s the 2025–2030 Dietary Guidelines for Americans range, to be adjusted to your calorie needs. With a smaller calorie budget, protein takes a larger share of each day, and how much protein per day to lose weight for a woman works through that in full. The table puts the range on a 1,400 kcal day at 4 kcal per gram.

Body weight	1.2 g/kg	1.6 g/kg	Share of a 1,400 kcal day
55 kg	66 g	88 g	19–25%
65 kg	78 g	104 g	22–30%
75 kg	90 g	120 g	26–34%
85 kg	102 g	136 g	29–39%

Protein’s acceptable range tops out at 35% of calories. The 85 kg row crosses it on a 1,400 kcal day. Use your own budget, because at a higher intake the same grams are a smaller share. The same range for any adult, with the 35% check, is in how much protein should I eat to lose weight.

Here’s what 1,277 kcal and about 99 g of protein looks like for a 65 kg woman. I built the day from USDA records, with the rice raw and the lentils boiled.

Meal	Food and grams	Energy	Protein
Breakfast	Rolled oats, 40 g	152 kcal	5.4 g
Breakfast	Greek yogurt, nonfat, 156 g	95 kcal	16.1 g
Breakfast	Banana, 115 g	101 kcal	0.9 g
Lunch	Boiled lentils, 198 g	230 kcal	17.9 g
Lunch	Eggs, 2 large, 100.6 g	148 kcal	12.5 g
Dinner	Braised chicken breast, 120 g	199 kcal	38.5 g
Dinner	Raw white rice, 50 g	185 kcal	3.5 g
Dinner	Raw broccoli, 150 g	48 kcal	3.9 g
Cooking	Olive oil, 13.5 g	119 kcal	0 g
Total		1,277 kcal	98.7 g

Each line is kcal per 100 g times the grams, for example 369.6 kcal per 100 g × 50 g = 185 kcal for the rice. The day leaves 123 kcal under a 1,400 kcal budget for tea with milk or a piece of fruit. The oil is 119 kcal, 9% of the day.

What changes for women: cycles, periods, pregnancy and breastfeeding?

Your cycle, pregnancy and breastfeeding each change the picture. Start with the cycle, which moves the scale. In one study of 42 women, body weight was 0.450 kg higher during menstruation than in the first week of the cycle, mostly from extracellular water. Studies disagree on the size, so compare the same days of different cycles.

Periods are a signal. The NHS lists sudden weight loss and doing too much exercise among the causes of missed or late periods, and says to see a GP if you miss three in a row. The International Olympic Committee’s consensus statement describes Relative Energy Deficiency in Sport as health and performance problems that follow low energy availability, meaning too little food for the energy you spend. If your periods stop while you diet or train hard, see your doctor before you cut further.

Pregnancy changes the target, and your midwife or doctor sets it. The NHS 12-week plan says it isn’t suitable for pregnant women. For breastfeeding, the NHS says a balanced diet and regular moderate exercise, such as a 30-minute brisk walk, won’t affect the quality or quantity of your milk. It gives no calorie number, so ask your midwife, health visitor or GP for yours.

Eating less leaves less room for nutrients. The 2025–2030 US guidelines single out healthy fats, iron and folate for women, so choose foods with more nutrients per calorie when your budget shrinks.

The plan above is for adults, so it isn’t for anyone under 18.

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.