If you’ve ever tried to lose weight, you’ve likely heard that a calorie deficit is required.

Yet, you may wonder what exactly it involves or why it’s necessary for weight loss.

This article explains everything you need to know about a calorie deficit, including what it is, how it affects weight loss, and how to achieve it in a healthy, sustainable way.

What it is and why it’s important for weight loss

Calories are the units of energy you get from foods and beverages, and when you consume fewer calories than you burn, you achieve a calorie deficit.

The calories you burn or expend each day — also known as calorie expenditure — include the following three components (1):

  • Resting energy expenditure (REE). REE refers to the calories your body uses at rest for functions that keep you alive, such as breathing and blood circulation.
  • Thermic effect of food. This involves the calories your body expends digesting, absorbing, and metabolizing food.
  • Activity energy expenditure. This refers to the calories you expend during sports like exercise and non-exercise related activities, including fidgeting and performing household chores.

If you provide your body fewer calories than it needs to support these three components of calorie expenditure, you put your body into a calorie deficit. Doing so consistently for long periods results in weight loss (1).

Conversely, you will gain weight if you regularly provide your body more calories than it needs to support these functions. This is called a calorie surplus.

summary

A calorie deficit occurs when you consistently provide your body with fewer calories than it needs to support calorie expenditure.

Calculating calorie needs

For most people, a calorie deficit of 500 calories per day is sufficient for weight loss and unlikely to significantly affect your hunger or energy levels (2).

To create this calorie deficit, you need to know what your maintenance calories are. Maintenance calories are precisely the number of calories your body needs to support energy expenditure.

You can use calorie calculators like the Body Weight Planner from the National Institute of Health. Such calculators estimate your maintenance calories based on your weight, sex, age, height, and physical activity level (3).

Though calorie calculators provide a good idea of your maintenance calorie needs, you can get a more precise number by tracking your calorie intake and weight for 10 days (4).

While maintaining the same level of daily activity, use a calorie tracking app to track your calories and weigh yourself daily. For an accurate result, use the same scale, at the same time of day, and wearing the same clothes (or nothing at all).

Your weight may fluctuate day to day, but if your weight has otherwise remained stable over the 10 days, the average number of calories you consumed per day is a better representation of your maintenance calories.

Divide the total number of calories you consumed for 10 days by 10 to find your average daily calorie intake. Then, subtract 500 calories from this number to determine your new daily intake goal for weight loss.

For example, if you find your maintenance calories to be 2,000 per day, your new daily calorie goal would be 1,500.

As you lose weight, your maintenance calories will decrease over time, and you will need to adjust your calorie intake based on your weight loss goals (1).

Still, to ensure healthy weight loss and adequate nutrient intake, women should not consume fewer than 1,200 calories per day, and men no fewer than 1,500 calories (5).

summary

You can estimate your maintenance calories by using an online calculator. Alternatively, for a more accurate number, monitor your calorie intake and weight for 10 days.

Ways to achieve a calorie deficit

You can achieve a calorie deficit by consuming fewer calories or increasing your physical activity levels — or both.

That said, it may be easier and more sustainable to create a calorie deficit through diet rather than exercise alone, as you may not have the time, energy, or motivation to exercise daily. Plus, exercise doesn’t burn as many calories as many people believe (6, 7, 8, 9, 10).

In other words, it may be easier to eat 500 fewer calories each day than to burn this number of calories through exercise. Nonetheless, it’s still recommended to engage in muscle-strengthening and aerobic exercises for their beneficial effects on overall health (11).

The Physical Activity Guidelines for Americans from the Department of Health and Human Services recommend that adults do 150–300 minutes of moderate-intensity exercise, or 75–150 minutes of vigorous-intensity exercise, weekly (12).

Moderate-intensity exercise includes brisk walking and light bicycling, whereas examples of vigorous-intensity exercise are jogging and fast bicycling.

The guidelines also recommend that adults do muscle-strengthening activities involving their major muscle groups — including the back, shoulders, chest, arms, and legs — at least two days every week (12).

Engaging in muscle-strengthening activities will help your body prioritize the loss of body fat rather than muscle mass (13, 14, 15).

summary

It’s likely more sustainable to create a calorie deficit through diet rather than exercise alone. However, physical activity is important for many aspects of health.

Tips for eating fewer calories

Cutting calories from your diet to create a calorie deficit doesn’t necessarily require drastic changes.

In fact, several strategies can help you reduce your calorie intake to lose weight and maintain it — and they don’t even require calorie counting.

Don’t drink your calories

You may be able to eliminate several hundred calories from your diet simply by reducing or eliminating your intake of sugary beverages like soda, fruit juices, and specialty coffee drinks.

Alcoholic beverages can also pack a significant number of calories.

The calories from these beverages don’t provide fullness, and in excess, they can lead to weight gain, heart disease, and diabetes (16, 17, 18, 19).

Limit highly processed foods

The sugar, fat, and salt in highly processed foods, including sugary beverages, fast foods, desserts, and breakfast cereals, make these high calorie foods highly palatable and encourage excess consumption (20, 21).

In fact, one study showed that people who were allowed to eat as much or as little as they wanted ate 500 more calories per day on a diet containing highly processed foods, compared with a diet containing minimally proceeded ones (22).

Minimally proceeded foods are rich in vitamins, minerals, and fiber and include foods like lean proteins, fruits, vegetables, nuts, and legumes. A diet rich in minimally processed foods will help prevent you from overeating and ensure you get the nutrients your body needs.

If your current diet consists of many highly processed foods, slowly begin to replace those items with minimally processed ones. For example, swap sugary cereals with oatmeal topped with fruit, or swap chips with lightly salted almonds.

Eat primarily home-cooked meals

Preparing and eating your meals at home allows you to control the ingredients and your portion sizes — and therefore, your calorie intake.

One study showed that people who cooked dinner at home 6–7 times per week consumed 137 fewer calories per day, on average, than people who cooked dinner at home 0–1 time per week (23).

Eating home-cooked meals is also associated with better diet quality, an increased intake of fruits and vegetables, lower body fat levels, and reduced risks of heart disease and diabetes (24).

What’s more, frequently cooking at home can save you money (25).

summary

Reducing your consumption of sugary beverages, consuming a diet containing mostly minimally processed food, and eating at home can help you reduce your calorie intake.

The bottom line

A calorie deficit occurs when you consume fewer calories than your body expends.

A calorie deficit of 500 calories per day is effective for healthy and sustainable weight loss.

Eliminating sugary beverages, consuming mostly minimally processed foods like fruits and vegetables, and eating home-cooked meals can help you reach a calorie deficit without calorie counting.