A person can create a calorie deficit by not consuming as many calories as they need to maintain their body weight during the course of a day or week. Over time, this calorie reduction can lead to weight loss.
This article covers everything a person needs to know about calorie deficits and weight loss.
A calorie deficit occurs when the number of calories a person consumes in a day is smaller than the number of calories they burn.
The body needs to burn a certain number of calories to perform all its functions each day.
How many calories a person needs each day varies based on their:
- physical activity levels
- body composition
Here are some estimated calorie needs for adults aged 19 years and over:
A person can create a calorie deficit by reducing the number of calories they eat, increasing their activity levels, or both.
Maintaining a calorie deficit is an important part of weight loss, but it is not the whole picture. This is because calories are not the only thing to affect weight.
To lose 1–2 pounds (lb) per week, a person would need to eat 500–1,000 calories fewer than the number of calories their body needs per day.
If a person is sedentary, meaning that they only move as much as they need to live independently but do not exercise or engage in other physical activities, they should start to get 30 minutes of exercise each day, if possible.
Also, the Centers for Disease Control and Prevention (CDC) state that cutting calories does not necessarily mean feeling unsatisfied at meals.
A person can replace some higher calorie foods with lower calorie foods, increase their water intake, and eat more fiber to feel full.
There are several ways to determine how many calories a person normally burns in a day.
For example, they can opt to calculate their daily calorie needs manually or find an online calculator.
To perform a manual calculation, moderately active people can multiply their current body weight by 15 to estimate how many calories they would need each day.
Then, to determine how many calories they should consume for a healthful calorie deficit, they can subtract roughly 500 calories from that number. However, people should ensure that they do not consume too few calories. It is also important to note that exercising can also contribute to a calorie deficit.
A person can also use their basal metabolic rate (BMR) and activity levels to determine their current caloric needs. They can use one of the following formulas to determine their BMR, according to their sex:
- adult male: 66 + (6.3 x body weight in lb) + (12.9 x height in inches) – (6.8 x age in years) = BMR
- adult female: 655 + (4.3 x weight in lb) + (4.7 x height in inches) – (4.7 x age in years) = BMR
Once a person has their BMR, they can use one of the following formulas, based on their activity levels, to determine their caloric need:
- sedentary: little or no exercise = BMR x 1.2
- minimally active: 1–3 days per week of exercise or activity = BMR x 1.375
- moderately active: 3–5 days per week of moderate activity or sports = BMR x 1.55
- very active: 6–7 days per week of hard exercise = BMR x 1.725
- extra active: athletes who train twice per day, for example = BMR x 1.9
People can also talk with their doctor or nutritionist for the most accurate caloric intake estimates. These professionals can tailor the estimate based on the person and their lifestyle.
Once a person knows how many calories they need each day or week, they can work on creating a calorie deficit.
One lb of body fat contains about 3,500 calories. For a person to lose 1 lb of fat in a week, they would need a deficit of 3,500 calories, or 500 calories per day, over that time. To lose 2 lb, a person would need a deficit of about 7,000 calories.
However, it is not advisable for a calorie deficit to exceed 7,000 calories per week.
One component in creating a calorie deficit is changing what a person eats and drinks each day. A person should focus on foods that are rich in nutrients but low in calories.
According to the Dietary Guidelines for Americans 2015–2020, a healthful eating pattern with fewer calories should include:
- vegetables, including dark green, red, orange, starchy, and other vegetables
- grains, at least half of which should be whole grains
- fruits, with a focus on whole fruits
- proteins, such as lean meats, poultry, eggs, legumes, nuts, soy products, and seafood
- low fat or fat-free dairy, including milk, yogurt, cheese, or fortified soy beverages
- healthful oils, such as olive oil, canola oil, or coconut oil
A person should also avoid consuming sugary drinks and trans fats.
They may also wish to increase the amount of water they drink, which will help them stay hydrated and replace any sugar sweetened beverages they usually consume.
An important part of weight loss is exercise. A person who is not active at all should try to increase their daily activity levels, if they can.
This can include activities such as:
- taking the stairs instead of the elevator
- playing a recreational sport
The CDC recommend that a person can do the following activities to meet moderate physical activity guidelines:
- brisk walking
- light snow shoveling
- doing light yard work
- biking at a casual pace
- actively playing with children
The more physically active a person is, the more calories they will burn.
This increases the number of calories they need, which can make creating a deficit easier.
Cutting calories is an important part of weight loss, but it is not the only consideration to make.
Physical activity is important for health beyond weight loss. People who are sedentary and move very little throughout the day should try to increase their daily activity levels, if possible. This can include exercising, playing sports, or participating in activities that require movement, such as hiking.
It is also important to note that counting calories is not necessary for weight management, and, in some cases, it may be counterproductive or harmful.
If a person cuts too many calories and does not get enough necessary nutrients, they can experience some health problems.
The body needs a minimum number of calories to function properly. Cutting too many can increase the risk of health issues, including:
- not getting enough nutrients, which can interfere with gaining or maintaining bone mass
- depriving the brain of necessary energy
- decreasing metabolism
- increasing the risk of developing gallstones
Some symptoms of not consuming enough calories include:
- getting sick frequently
- being unable to lose weight
- experiencing negative changes in mood or behavior
- having difficulty sleeping
- experiencing constipation
Before cutting calories, a person should talk with their doctor or nutritionist. People with specific health conditions, such as diabetes, may need specialized diets to help them manage their condition.
Creating a calorie deficit may be helpful if a person wishes or needs to lose weight. A person can do this using a combination of diet and exercise.
They should try to focus on eating highly nutritious foods, drinking more water, and exercising regularly.
Formulas and online calculators are available to help people estimate how many calories they burn per day. From there, a person can estimate how many calories they should eat to create a calorie deficit.
A person should aim to lose no more than 1–2 lb per week to avoid potential health issues associated with not getting enough nutrients.