What Is A Calorie Deficit?

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We often hear this saying, “Do you know how many calories you eat every day?” Calorie plays a crucial role in our day-to-day food habits and physical wellbeing. Nowadays people have become more health conscious and they apply various strategies to improve their fitness, weight control, and diet. Excess calorie intake causes various issues and hence many people adopt a strategy called Calorie deficit, so what is calorie deficit? 

Consumption of food provides energy to us. A unit of energy received from the food is called a calorie. A calorie deficit occurs when we take fewer calories than required or burn more energy to cause low-calorie intake to our body.1 The three possible ways to achieve this calorie deficit include:

  • Increase the burning of calories through exercise
  • Taking fewer calories than usual
  • Doing both of the strategies to achieve a calorie deficit2

What are the factors determining calorie deficit? How to achieve it?

The three factors that affect the calorie deficit include:

  • Basal Metabolic Rate: Your body requires a certain amount of energy to function, which is known as the basal metabolic rate, or BMR. A person's BMR is influenced by several variables, including age, gender, height, and weight
  • Physical exercise: Up to 40% of your daily caloric needs come from any kind of physical exercise. Exercise is a part of this as well
  • Thermic effect of food: The energy required to break down and assimilate the food you eat is known as the thermic effect of food1

It is important to have a safe calorie deficit because low calories may lead to unwanted effects on our body and cause various problems. Here are simple steps to have a calorie deficit:

  • The simple way to achieve a calorie deficit includes if you have to burn 600 calories, reduce 300  calories through exercise and 300 calories through diet
  • Intermittent fasting is also an effective method which includes avoiding eating for a certain period2  

One important factor to note is that people are too fast and require instant results. If you are planning for a Calorie deficit, do not start with a big calorie deficit at the beginning. Start with a small amount because a sudden calorie deficit can cause various issues in the body:

  • Fatigue
  • Nausea
  • Dehydration
  • Constipation
  • Headaches
  • Crabbiness

Pros and Cons of Calorie Deficit

Effective calorie deficits can lead to weight loss. Those who consumed 12% fewer calories per day than their regular diets lost 10% of their body weight, according to a two-year study involving over 200 participants. In the same study, individuals who were able to create a calorie deficit also saw drops in thyroid hormones, inflammatory markers, blood pressure, and cholesterol. There is some evidence linking the latter two results to a lower risk of age-related diseases and a longer lifetime. Studies have indicated that those who reduce their caloric intake report better quality of life, mood, and sleep than those who do not make any dietary changes. According to the findings of another study, calorie restriction is still the most effective strategy for treating and preventing obesity in adults. 

A large or prolonged calorie deficiency can pose health hazards. An excessive reduction in calorie deficit, like a 40% reduction in calorie consumption for six months, has been proven to cause negative effects that include:

  • Loss of muscle mass
  • Nutrient deficiencies
  • Chronic weakness
  • Lowered aerobic capacity ( lower oxygen capacity during exercise)
  • Severe emotional distress, including suicidal thoughts

According to some studies, people who establish a calorie deficit may experience brief episodes of anaemia, which is a reduction in the number of red blood cells that deliver oxygen throughout the body. They may also have small decreases in bone density, lean body mass, and aerobic ability.2

Weight loss and Calorie deficit: Is calorie deficit a new strategy to lose weight?

Carbohydrates, lipids, and proteins are calorie-containing foods that serve as your body's primary energy source. Calories come from various sources, they are either turned into physical energy or stored as fat in your body. These stored calories will remain in your body as fat unless they are used up. It causes weight gain. You can do weight loss by reducing the number of calories you consume, forcing your body to rely on its stores for energy. Or you can increase your physical activity to burn more calories. Your weight is a balancing act, but the equation is clear. You can lose weight by eating fewer calories and burning more calories through physical activity. Previous researchers discovered that 3,500 calories of energy equaled around 1 pound (0.45 kilogram) of fat. So, researchers assumed that burning or cutting 500 calories per day resulted in a weekly weight loss of one pound. However, this is not true for everyone. Typically, reducing 500 calories per day can result in a weekly weight loss of ½ to 1 pound. However, this can vary according to your body type, desired weight loss, gender, and level of physical activity.Reducing calories have an impact on weight management but before starting a low-calorie diet  or calorie deficit, consult your physician or dietitian to get personalised diet requirements at a normal level without drastically cutting out calories.

Key Takeaways

Calorie deficit is an important aspect of diet planning to reduce weight and improve overall well being. Everyone is unique and we eat different types of food and our body gets adapted to our daily food habits and physical activity. If you are planning to reduce your daily intake of calories, it is crucial to start calorie deficit at a lower level and increase it gradually. Don't expect instant results. If you are consistent, you will have steady results after daily practice. Consult your physician before planning for a low-calorie diet, because your body should to the low-calorie diet and you should not lose energy and feel fatigued. Have a checklist of the food and the calories you take everyday and do a tracking of calories you burn everyday through exercise so that it could be effective management. Remember these key takeaways, have a healthy start, and be happy!


What are the effects of calorie deficit in your body?

Starting with a low-calorie deficit will not have much effect on your body but a large amount can cause some effects such as fatigue, nausea, vomiting, and constipation. If you find any effects consult a physician and stop the diet immediately

Does a calorie deficit cause severe health issues?

Studies are reporting severe health issues only if the diet is followed for a longer period of time with a huge low-calorie deficit at the beginning. Hence you need not worry about it unless you do a large calorie deficit.

Is calorie deficit an effective way to reduce weight?

Calorie deficit plays an important role in weight management, you can start the weight loss regime in the simplest calorie deficit diet along with physical exercise to burn the excess fat in your body.

How can you maintain a calorie deficit and healthy food habits?

Have a diet plan from a dietitian with a low-calorie diet without causing much loss of energy to your body. It helps you in effective balance.

Is it mandatory to consult a dietitian before starting a calorie-deficit diet?

It is good to consult a dietitian because they can know well about your current food habits and they will effectively modify your diet so that you can get the intended results of a calorie deficit diet.


  1. HealthifyMe [Internet]. 2022 [cited 2024 Feb 24]. Calorie deficit diet - all you need to know - blog. Available from: https://www.healthifyme.com/blog/calorie-deficit-diet/
  2. Health [Internet]. [cited 2024 Feb 24]. What is a calorie deficit—and how do you reach it? Available from: https://www.health.com/calorie-deficit-7375266
  3. Cleveland Clinic [Internet]. [cited 2024 Feb 24]. What is calorie deficit? Available from: https://health.clevelandclinic.org/calorie-deficit
  4. Mayo Clinic [Internet]. [cited 2024 Feb 24]. Counting calories: Get back to weight-loss basics. Available from: https://www.mayoclinic.org/healthy-lifestyle/weight-loss/in-depth/calories/art-20048065

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Koushika M

Master's degree, Medicinal and Pharmaceutical Chemistry, SRMIST, Kattankulathur, Chennai, Tamil Nadu

Koushika is a freelance writer with strong background in the field of Pharmaceutical Sciences. She has an expertise of combining her medical knowledge with writing and provide reliable health content.

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