What Is a Calorie Deficit?

A calorie deficit is when you burn more calories than you eat or drink.

You're probably familiar with the notion of a deficit as it relates to money. In that sense, a deficit occurs when the amount you owe is more than what you have, which is not a good thing.

When it comes to calories, a deficit is something many people strive for as a way to lose weight. Yet the concept isn't as straightforward when it applies to your body as it is with your bank account.

Here are some explanations for what "calorie deficit" means and how to go about using a calorie-based approach to weight loss.

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What Is a Calorie Deficit?

A calorie deficit occurs when you consume fewer calories than your body expends. There are two ways to achieve a calorie deficit.

Method One: Eat Fewer Calories

The first is to consume fewer calories than it takes to maintain your current weight. You can start by using an equation to estimate the number of calories your body needs to maintain your weight. There are several research-based formulas that determine this, including the Mifflin-St Jeor formula.

This has been referred to by researchers and the nutrition community as the most reliable at predicting your resting metabolic rate, or the total number of calories you burn when your body is completely at rest.

If you don't want to do the math yourself, use a handy online calorie-needs calculator. The tool asks for your age, height, weight, sex, and activity level since each of these factors determines your calorie needs.

For example, a 40-year-old, 5'4" person assigned female at birth who weighs 150 pounds and is inactive needs about 1,700 calories to maintain their weight, according to the calculator. If they consume fewer than 1,700 calories, they have created a calorie deficit.

Method Two: Burn More Calories Than You Consume

The second way to create a calorie deficit is to burn more calories than you consume. To use this method, the 40-year-old person from the example above could eat 1,700 calories but start being more active. If they burn an additional 300 calories by adding a brisk walk to their day, they've created a calorie deficit.

How To Create a Calorie Deficit Safely

If you want to lose weight with calorie deficits, creating a calorie deficit that's too large for too long can be hard on your body. For example, if it takes 1,700 calories to maintain your weight, and you start eating 1,000 calories a day, that's a pretty drastic drop.

When workouts are added to the mix, you can seriously stress your body. You're also depriving your cells of nutrients needed for the recovery from the wear and tear exercise puts on the body and for vital daily functions like circulation.

Over time, such a big deficit can result in unwanted side effects, such as a slower metabolism and digestive health issues (e.g., constipation).

Support Your Ideal or Healthy Weight

Try to consume what it takes to support your ideal or healthy weight for an extended period of time. Additionally, remember that your calorie needs will be different than someone else's needs.

If you weigh 150 pounds and your ideal weight is 130 pounds, enter 130 into the calorie-needs calculator. This ensures that you won't drop below the number of calories needed to support overall wellness at a healthy weight.

Eating only enough to support your target weight may help you eventually reach and maintain that weight. (That is if your calorie-based strategy is paired with paying attention to other key elements, like food quality and management of your medical conditions.) Not only is this approach healthier, but it can be more practical in the long term.

What Else To Know About Calorie Deficits and Weight Loss

There are other things to consider about calorie deficits and weight loss.

You Likely Can’t Only Depend on a Calorie Deficit To Lose Weight

For years, experts relied on the notion that 3,500 calories equal one pound. That led to the idea that producing a deficit of 500 calories per day would lead to a one-pound weight loss per week (since 500 x 7 = 3,500).

Also, burning calories through exercise was another way for calorie deficits to lead to weight loss. According to the math above, cutting and burning 500 calories every day for a total of 1,000 calories would result in a two-pound loss per week.

Unfortunately, if you've ever experimented with this approach, you've probably found that it's not quite that simple. Nutrition and metabolism are far more complex than a simple calories-in-vs-calories-out equation.

Many factors impact weight-loss results and the rate of weight loss, including:

  • Quality of the calories consumed (whole vs processed foods)
  • Macronutrient balance
  • Meal timing
  • Hormones
  • Stress
  • Sleep
  • Genetics
  • Gut microbiota makeup
  • Underlying health conditions
  • Medications

Plus, not all calories are created equal. A 500-calorie blueberry muffin made with white flour and refined sugar will have a very different effect on your body than a 500-calorie bowl of cooked oats topped with blueberries and walnuts. That's not to say that calories don't matter, but they're not the sole determinant of weight management.

Weight Loss Takes Patience

If you want to lose weight, take a slow and safe approach. In fact, people who lose one to two pounds per week are more successful at keeping weight off (the ultimate goal).

While many people would like to lose weight faster, even modest weight loss has been shown to result in health benefits, such as improvements in blood pressure, cholesterol, and blood sugar.

Keep in mind that the closer you are to your weight goal, the smaller the deficit between the calories needed to maintain your weight and the number required to support your ideal weight. That means even slower results, perhaps even less than a pound per week. But if you remain focused on feeling well along the way, it's well worth the wait.

A Quick Review

Achieving a calorie deficit by consuming fewer calories or burning more calories than we consume are ways to reduce weight. However, calorie deficits have to be approached cautiously. Over time, a large calorie deficit can result in a number of unwanted side effects, including the loss of muscle tissue, reduced immune function, poor digestive health, and irritability.

Our bodies are complex. If you're a math person, or you like to use food and/or exercise trackers, you're probably very aware of calories. Just be sure to keep in mind that calories are only one piece of the weight management puzzle.

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11 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Academy of Sports Medicine. Resting metabolic rate: how to calculate and improve yours.

  2. National Academy of Sports Medicine. Calorie calculator.

  3. Kaufman C. 4 ways low-calorie diets can sabotage your health. Eat Right.

  4. Centers for Disease Control and Prevention. Finding a balance of food and activity.

  5. Thomas DM, Gonzalez MC, Pereira AZ, Redman LM, Heymsfield SB. Time to correctly predict the amount of weight loss with dietingJournal of the Academy of Nutrition and Dietetics. 2014;114(6):857-861. doi:10.1016/j.jand.2014.02.003

  6. Egan AM, Collins AL. Dynamic changes in energy expenditure in response to underfeeding: a reviewProc Nutr Soc. 2022;81(2):199-212. doi:10.1017/S0029665121003669

  7. Kim JY. Optimal diet strategies for weight loss and weight loss maintenanceJournal of Obesity & Metabolic Syndrome. 2021;30(1):20-31. doi:10.7570/jomes20065

  8. Stanislawski MA, Frank DN, Borengasser SJ, et al. The gut microbiota during a behavioral weight loss interventionNutrients. 2021;13(9):3248. doi:10.3390/nu13093248

  9. National Institute of Diabetes and Digestive and Kidney Diseases. Factors affecting weight & health.

  10. Centers for Disease Control and Prevention. Eat more, weigh less?

  11. Centers for Disease Control and Prevention. Losing weight.

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