How many calories should I eat to lose weight?

To lose weight, you eat fewer calories than you burn. A common starting point is your estimated daily burn minus 500 calories, within the 500 to 750 calorie deficit a 2026 US guideline gives for intensive weight loss programs.^[26] Treat that number as a first guess and adjust it after a few weeks of real results, since weight lost at about 1 to 2 pounds a week is more likely to stay off.^{[6, 1]}

Step 1: estimate what you burn in a day

Your body uses energy in three ways. Resting burn, the energy that keeps you alive at rest, is the biggest part, typically 60 to 70 percent of the total.^[7] Digesting food uses about 10 percent.^[7] Movement is the part that changes most, from 15 percent for inactive people to 50 percent for physically active people.^[7]

Resting metabolic rate (RMR)

The calories your body burns at rest in a day, also called resting energy expenditure. Basal metabolic rate (BMR) is a related, slightly lower measure.^[7] This guide calls it resting burn.

The most common way to estimate resting burn is the Mifflin-St Jeor equation, from a 1990 study of 498 healthy adults.^[3] A review of the four most used equations found it was the most reliable of them.^[4]

One shortcut to total daily burn multiplies resting burn by an activity factor.

Dalia uses five of these factors for a starting target: sedentary (desk job, little exercise) 1.2, lightly active (1 to 2 workouts a week) 1.375, moderately active (3 to 4) 1.55, very active (5 or more) 1.725, and athlete (hard training every day) 1.9. The National Academies takes a different approach, with separate equations for four activity levels.^[8]

Step 2: subtract a modest amount

A 2026 US guideline says intensive weight loss programs should aim for a calorie deficit of 500 to 750 calories a day.^[26] The older 2013 US obesity guideline gave clinicians a set range of 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men, usually adjusted for body weight.^[2] In the UK, the NHS suggests cutting about 600 calories a day.^[11]

Dalia's app offers three paces, 0.5, 1 or 1.5 pounds a week, which it turns into a cut of 250, 500 or 750 calories a day.

For comparison, take adults of average height at a healthy weight. The 2020–2025 edition of the US Dietary Guidelines estimated that women like this need 1,600 to 2,400 calories a day to keep their weight steady, and men need 2,000 to 3,000.^[23] The current 2025–2030 edition gives no ranges and says the calories you need depend on your age, sex, height, weight and activity.^[25]

Both methods carry error for one person. The National Academies equation for women has a typical error of 246 calories a day.^[6] That is why the next step matters more than the formula.

Step 3: adjust from what the scale does

The National Academies calls planning intake a two-step process: estimate, then watch your weight over time and adjust.^[6] Weighing yourself at least once a week is one feature of programs that work.^[22]

• US and UK advice both aim for about 1 to 2 pounds a week.^{[1, 12]} If you are losing faster than that, a slightly higher target puts you back in the pace linked to keeping weight off.^[1]
• If nothing has moved after a few weeks, check your log first. People often underestimate how much they eat. It is the most common error in food logs.^{[6, 24]}
• In one small study of 10 people with obesity who said they could not lose weight, they underreported what they ate by 47% on average.^[18] Their metabolism was within 5 percent of what was predicted.^[18]

Why "a pound a week" slows down

The old rule says a 3,500-calorie deficit makes one pound of loss, so 500 calories a day is a pound a week.^[10] It overstates loss, because a smaller body burns less as weight comes off.^{[9, 10]}

In 7 supervised studies, people lost 20.1 pounds on average, 7.4 pounds less than the rule predicted.^[10] NIH researchers built a model with a better rule of thumb for an average adult with overweight.^[9] Each 10 calories a day of steady change leads to about 1 pound of change in the end, and half of it comes in about a year.^[9]

The authors of the 7-study comparison suggest tools built on such models instead.^[10] One is the NIH body weight simulator, which now opens as the Body Weight Planner.^{[10, 24]} Dalia uses the simple rule for a starting target, then reads your weigh-ins against it.

Whether your metabolism also slows by extra is disputed. In 14 contestants from The Biggest Loser, resting burn was about 499 calories a day lower than expected 6 years later.^[15] In 171 women with overweight, the extra slowdown was small, about 54 calories a day, and did not predict regain.^[16] Researchers still disagree about how much this matters.

How low is too low?

Dalia's app never sets a daily target below 1,200 calories, for anyone. Guidelines draw their lines differently.

The 2013 US obesity guideline prescribed 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men in clinician-led programs.^[2] It kept diets under 800 calories a day for medical settings only.^[2] It warned that weight comes off fast on them, and problems can follow.^[2]

In the UK, NICE keeps diets of 800 to 1,200 calories a day for specialist weight services, or services for conditions like type 2 diabetes.^[13] Even there, they last no more than 12 weeks.^[13] Fast weight loss may also raise the chance of gallstones.^[14]

Protein helps a little. Across 24 trials, people on higher protein diets with the same calories lost about 0.43 kg less fat-free mass.^[17] The authors call the benefits modest.^[17]

When to talk to a clinician