How Many Calories Should I Eat to Lose Weight?

Key takeaways

• It depends on what you burn now. The 2013 AHA, ACC and TOS guideline describes a deficit of 500 or 750 calories a day, or about 30 percent, with calorie levels adjusted for body weight and activity.¹
• The same guideline lists set ranges of 1,200 to 1,500 calories a day for women and 1,500 to 1,800 for men, and keeps diets under 800 calories inside medically supervised programs.¹
• Loss runs slower than the arithmetic. The 1998 NHLBI guideline found typical losses over 6 months of 20 to 25 pounds, where the math predicted 26 to 52.²
• Treat any calculator as a first guess, and correct it with 2 to 4 weeks of complete food logs and your weekly average weight.

How many calories should you eat to lose weight?

It depends on how many calories you burn now, which depends on your size and how active you are. The 2013 obesity guideline from the AHA, ACC and TOS describes three ways clinical programs set a lower intake, a deficit of 500 or 750 calories a day, a deficit of about 30 percent, or a set daily range. It notes that calorie levels are usually adjusted for body weight and physical activity.¹

So the first number to find is your own maintenance, the calories that keep your weight steady. The TDEE guide explains how to estimate it and then correct it from your log.

How to calculate a calorie deficit

A calorie deficit is the gap between the calories you burn and the calories you eat. Guidelines describe it as a reduction from your usual intake. The 1998 NHLBI guideline, for example, lists a reduction of about 500 to 1,000 calories a day from usual intake.²

• Estimate your maintenance calories with a TDEE calculator.
• Read the deficits guidelines describe, in the table below, and talk them over with your clinician if you have a health condition.
• For a personal calorie number, use the calorie deficit calculator and go over the result with your clinician.
• Log everything you eat and drink for 2 to 4 weeks.
• Compare your average intake with the change in your weekly average weight. The TDEE guide shows how that tells you your real maintenance, which you can take back to the calculator or your clinician.

What do guidelines say about calorie levels?

These numbers describe how clinical weight-loss programs are set up. They aren't goals to aim for, and a lower number isn't a better one. NHLBI notes that a greater rate of weight loss doesn't give a better result at the end of 1 year.²

For the risks of going lower, read the guide on how big of a calorie deficit is safe.

Why weight loss is slower than the math

The 1998 NHLBI guideline ran the numbers itself. Over 6 months, a deficit of 500 to 1,000 calories a day should in theory produce a loss of 26 to 52 pounds. The average loss actually seen over that time was usually 20 to 25 pounds. After about 6 months, the rate of loss usually slows and levels off.²

Hall and Chow, writing in 2013, called the failure to account for changing energy balance the most serious error of the 3,500 calorie per pound rule. The deficit you start with doesn't stay fixed as your weight changes.⁴

Hall's 2011 model shows why. A heavier body needs more calories to stay the same, so as weight falls, maintenance falls too, and the same intake makes a smaller gap. The model put the half time of the body's response at about 1 year, and people with more body fat had a larger expected change for the same change in intake.³

How to check your number with a food log

Your weight trend is the check on any calculator. If your weekly average weight holds steady across a few weeks of complete logs, your average intake is close to your maintenance, whatever the calculator said. If it falls faster or slower than you expected, your real maintenance is higher or lower than the estimate.³

Compare weekly averages, not single mornings. Food, water and salt move the scale from day to day, and the guides on water weight and the best time to weigh yourself cover how to read it.

The NIH Body Weight Planner, a free tool from NIDDK, works out calorie levels to reach a goal weight in a time you choose and to stay there afterward. NIDDK notes that it isn't medical advice.⁵

When to talk with a clinician

Talk with your doctor before changing how you eat if you're pregnant or breastfeeding, take medicine for diabetes or blood pressure, or have had an eating disorder. If your intake keeps falling under 1,000 calories a day, or counting calories brings up worry about food, a doctor or a registered dietitian can help.

A note on medical advice

This article is for general information and isn't medical advice. Talk with your clinician about your own situation.

Worked example

Here's the arithmetic the 1998 NHLBI guideline checked. At 3,500 calories per pound, a deficit of 500 calories a day works out to 1 pound a week, or 26 pounds over 26 weeks, and a deficit of 1,000 doubles that to 52. Those are the 26 to 52 pounds the guideline calls the theoretical result for 6 months. The average loss it reports actually seeing over that time was usually 20 to 25 pounds, because the deficit doesn't stay fixed as weight changes.²⁴

A closer look

Calculators that turn 500 calories a day into a pound a week skip a check the 1998 NHLBI guideline made. Over 6 months, a deficit of 500 to 1,000 calories a day predicts a loss of 26 to 52 pounds, but the average loss actually seen was usually 20 to 25 pounds, and a faster rate of loss didn't give a better result at 1 year.²

Questions and answers

Related guides

• How to track calories
• What is TDEE?
• How big of a calorie deficit is safe?
• Best time to weigh yourself
• Water weight vs fat loss
• How much protein to eat when losing weight
• TDEE calculator
• Calorie deficit calculator

Sources

1. Circulation. Jensen. 2014.
2. Obesity Education Initiative, The Evidence Report. NHLBI. 1998.
3. Lancet. Hall. 2011.
4. International Journal of Obesity. Hall, Chow. 2013.
5. Body Weight Planner. NIDDK. 2026.