What Is a Calorie Deficit—And How Do You Reach It?

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d3sign / Getty Images

Medically reviewed by Aviv Joshua, MS

A calorie deficit means that the number of calories you burn exceeds the number of calories you eat, which results in weight loss.

There are three possible ways to achieve a calorie deficit. The first is to increase the number of calories you burn through exercise. The second is to reduce your calorie intake through diet. The third is to do a little of both.

Achieving a calorie deficit can be beneficial for weight loss and overall health, but creating a calorie deficit that’s too large can lead to health risks. It's important to talk to a healthcare provider before starting a calorie deficit in order to lose weight safely and effectively.

How Do You Safely Reach a Calorie Deficit?

The safest way to achieve a calorie deficit is to make changes that allow you to burn more calories than you eat while still properly nourishing your body.

You can reach a calorie deficit by reducing your calorie intake or increasing your calorie output through physical activity. You can also do both together. For example, you’ll create a 500-calorie deficit by cutting 250 calories from your diet per day and burning an additional 250 calories through exercise.

You can also cut calories through intermittent fasting, which involves avoiding eating for a certain period of time. There are four methods for intermittent fasting:

  • Time-restricted feeding involves limiting your eating window to a certain number of hours per day and fasting for the remainder of the 24-hour period. For example, a 16:8 intermittent fast means you fast for 16 hours per day and eat within an eight-hour time frame, such as 9am to 5pm or 12pm to 8pm.

  • Alternate day fasting means you eat a minimal number of calories every other day and follow your usual eating pattern on the alternate days.

  • 5:2 fasting means you limit your calories two days per week and eat normally five days each week.

  • Periodic fasting involves restricting calories for multiple consecutive days, such as 5 days in a row once a month with no fasting on the remaining days.

How Do You Figure Out Your Calorie Deficit?

To determine how to achieve a calorie deficit, you first need to choose an approach. If you’d like to reduce your calorie consumption through intermittent fasting, choose one of the four methods listed above.

If you plan to achieve a deficit by increasing your calorie output through exercise, you'll need to track the amount of calories you burn.

Based on your weight and activity type and length, you can estimate how many calories you'll burn in a workout. For example, a 154-pound person will burn 280 calories walking at 3.5 miles per hour for one hour.

You can also use a wearable tracker device to measure your activity and personal calorie output throughout the day.

If you are creating a deficit by reducing the amount of calories you consume, it may be helpful to track your meals, snacks, and beverages using a nutrition app. Seeing where your calories come from can help you decide how and when to cut back.

For example, you can lower your daily calorie intake by:

  • Replacing a higher calorie food with lower calorie alternative. Swap ¾ cup cooked white rice with riced cauliflower to save 120 calories.

  • Reducing your portion sizes. Eat one slice of a 14-inch cheese pizza instead of two to save 236 calories.

  • Cutting out sugary beverages. Drink 12-ounces of water instead of 12-ounces of ginger ale to save 124 calories.

Keep in mind that once you achieve a calorie deficit, it can be difficult to predict the amount and rate of weight loss you’ll experience. Each person's metabolism and activity level is different, both of which can play a role in calorie outputs.

Benefits of a Calorie Deficit

When done safely, achieving a calorie deficit has many potential benefits. A calorie deficit accomplished through an increase in physical activity may result in reductions in:

  • High blood pressure

  • Risk of type 2 diabetes, heart attack, stroke, and some cancers

  • Arthritis pain and disability

  • Osteoporosis (bone disease) and falls

  • Symptoms of depression and anxiety

Successful calorie deficits may also result in weight loss. A two-year study of over 200 people found those who consumed 12% fewer calories per day than their typical diets lost 10% of their body weight.

In the same study, those who achieved a calorie deficit also had reductions in blood pressure and cholesterol as well as inflammatory factors and thyroid hormones. There is some evidence that the latter two outcomes are tied to longer lifespan and reduced age-related disease risk.

Other research has shown calorie restrictors experience improvements in quality of life, mood, and sleep compared to those who did not change their calorie consumption.

Another study concluded that in humans, calorie restriction remains the best way to prevent and treat obesity and its complications. Researchers noted that moderate calorie restriction can offer health benefits even in people who do not have obesity. This was true whether the calorie restriction was achieved through intermittent fasting or restricted eating combined with regular exercise.

Risks of a Calorie Deficit

When a calorie deficit is too large or goes on for too long, it can lead to health risks. An excessive ongoing calorie deficit, such as a 40% reduction in calorie intake for six months, has been shown to result in side effects that include:

  • Loss of muscle mass

  • Nutrient deficiencies

  • Chronic weakness

  • Lowered aerobic capacity (a reduction in the body’s ability to use oxygen during exercise)

  • Loss of sex drive

  • Severe emotional distress, including suicidal thoughts

Calorie deficits that result in rapid weight loss, which means over two pounds per week for several weeks, can also lead to:

  • Gallstones

  • Gout (inflammatory arthritis)

  • Fatigue

  • Nausea

  • Constipation or diarrhea

  • Muscle loss

Some research has shown those who achieve a calorie deficit may experience brief episodes of anemia, a reduced number of red blood cells that carry oxygen throughout the body. They may also experience slight declines in bone density, lean body mass, and aerobic capacity.

However, these declines may be expected with rapid or significant weight loss. Combining physical activity with a calorie restriction can help protect against the loss of bone, muscle, and aerobic capacity.

A Quick Review

When done correctly, achieving a calorie deficit can help promote weight loss and support overall health. You can create a calorie deficit by limiting the calories you eat, exercising to burn more calories, or by doing both together.

For safety and effectiveness, avoid creating a calorie deficit that is too large and make sure to follow regular eating pattern that keeps your properly nourished. For customized guidance on how to choose a calorie deficit method that’s right for you, talk with your personal healthcare provider.    

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Read the original article on Health.