A calorie deficit means that the number of calories you burn exceeds the number of calories you eat, resulting in weight loss. Essentially it means eating less than the energy you use.
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 and is challenging to maintain. It's important to talk to a healthcare provider before starting a calorie deficit to lose weight safely and effectively. Learn more about using a calorie deficit to achieve your health goals.
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. Gradual and less drastic changes are often easier to stick to over time.
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 length of time. There are four methods for intermittent fasting:
- 5:2 fasting means you limit your calories two days per week and eat normally five days each week.
- Alternate-day fasting means you eat a minimal number of calories every other day and follow your usual eating pattern on alternate days.
- Periodic fasting involves limiting calories for a few days in a row once a month, then eating regularly on non-fasting days.
- Time-restricted feeding involves limiting your eating window to a certain number of hours per day and fasting for the remainder of the 24 hours. 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 9 am to 5 pm or 12 pm to 8 pm.
How Do You Determine Your Calorie Deficit?
To determine how to achieve a calorie deficit, you first need to choose how. If you’d like to reduce your calorie consumption through intermittent fasting, you could opt for one of the above approaches.
If you plan to create a deficit by increasing your calorie output through exercise, you'll need to track the amount of calories you burn. Aim to burn more calories than you consume.
Based on your weight and activity type, intensity, 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 number 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:
- Cutting out sugary beverages. Drink 12 ounces of water instead of 12 ounces of ginger ale to save 124 calories.
- Reducing your portion sizes. Eat one slice of a 14-inch cheese pizza instead of two to save 236 calories.
- Replacing a higher calorie food with a lower calorie alternative. Swap 3/4 cup cooked white rice with riced cauliflower to save 120 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 are different, both of which can play a role in calorie outputs.
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:
- Arthritis pain and disability
- High blood pressure
- Osteoporosis (bone disease) and falls
- Risk of type 2 diabetes, heart attack, stroke, and some cancers
- 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 that people who restrict calories experience improvements in quality of life, mood, and sleep compared to those who do 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:
- Chronic weakness
- Loss of muscle mass
- Loss of sex drive
- Lowered aerobic capacity (a reduction in the body’s ability to use oxygen during exercise)
- Nutrient deficiencies
- 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:
- Constipation or diarrhea
- Fatigue
- Gallstones
- Gout (inflammatory arthritis)
- Muscle loss
- Nausea
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.
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 doing both together.
For safety and effectiveness, avoid creating a calorie deficit that is too large, and make sure to follow a regular eating pattern that keeps you properly nourished. For customized guidance on how to choose a calorie deficit method that’s right for you, talk with a healthcare provider.
