How to Calculate your Calorie Deficit for Weight Loss

So you’ve set your goals on losing weight and you’re trying to get your diet in order. You’ve made the first step by checking out your calories but all of the online calculators just leave you confused. Here’s everything you need to know to calculate your calorie deficit and make sure you lose weight.

What is a Calorie?

From a physics perspective, a calorie is the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. With respect to nutrition, this is the energy contained in food to do the same amount of work.

However, the calories from food are actually kilocalories (1000 calories) but for convenience they are called by the same name. In essence, calories are the energy you get from food.

Why does a Calorie Deficit matter?

The body can use the energy or calories it gets from food in several ways. It can use the energy in order to perform work. This can be just to maintain regular body functioning (basal metabolic rate) or it can be to perform movements such as exercise.

On the other hand, if this energy is not utilized by the body then there will be a surplus of energy. The body wants to keep this energy for times of scarcity so it stores it in the form of fat.

Therefore, by consuming less calories than your body needs, it will be forced to depend upon these energy stores and burn its fat reserves.

Hence, it is important to maintain a calorie deficit in order to lose weight.

How to Calculate your Calorie Deficit?

You can use this calculator in order to get a rough estimate of your daily caloric needs to lose weight. However, to make sure you effectively lose weight and don’t have any setbacks I suggest you read ahead.

Step 1 – Calculate Your Basal Metabolic Rate

Your basal metabolic rate (BMR) is the energy or calories your body needs in order to keep the body functioning at rest. It makes up roughly 70% of your daily energy expenditure.

Several factors impact your basal metabolic rate:

• Genetics
• Gender
• Age
• Weight
• Lean body mass

Of course, you can’t definitively quantify your basal metabolic rate but you can get a rough estimate using several calculations. The most accurate formula is the Mifflin-St. Jeor Equation:

BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + G

G depends on your gender. For males, G = +5 and for females, G= -161.

This formula, or any other BMR formula, will give you a rough estimation of your basal metabolic rate which we will use to calculate your calorie needs. Don’t worry, we’ll talk about correcting the estimation later on.

Step 2 – Calculate Your Maintenance Calories

Of course, your body isn’t laying in one spot all day. Its doing a lot more than just surviving. You’ll use a lot more energy in order to move around.

Therefore, your level of activity can determine just how many calories your body needs in order to function on a daily basis. This is your maintenance calories.

Your level of activity can be:

• Sedentary – little or no movement.
• Light – light exercise up to 3 days per week or with an office job.
• Moderate – hard exercise 6-7 days per week or performing manual labour.
• Very Active – Hard exercise everyday.
• Extra Active – Hard exercise multiple times per day such as a professional athlete.

You can estimate your daily maintenance calories by determining which criteria best describes you and applying a multiplier to your BMR calculation.

Maintenance Calories = BMR x Multiplier

Again, this is only an estimate of your daily calorie needs and we will discuss how to adjust this number to be more accurate later.

Step 3 – How big of a Calorie Deficit to Lose Weight?

You’ve already calculated your maintenance calories so you have a guide as to how much energy your body needs on a daily basis. Therefore, in order to burn fat we will need to ensure we consume less energy than we burn. But how much calories is enough?

It is generally considered that in order to burn 1 pound of fat you need to burn 3500 calories. This translates to a calorie deficit of 500 calories per day in order to lose 1 pound per week.

In order to lose 2lbs per week, this figure would double and you would be required to create a calorie deficit of 1000 calories per day.

So why not aim for more?

The Risk of a too large Calorie Deficit

You might be tempted to slash calories drastically in order to lose as much weight as possible. However, your fat reserves are only one source of stored energy in your body and you can only burn as much fat as you can metabolize.

With a calorie deficit that is too big, you will inevitably also break down lean body tissue such as muscle in order to meet the demands of your body. This is not only unhealthy but will result in a less aesthetically pleasing physique once the fat is gone.

It’s best to go slowly with your weight loss with a moderate calorie deficit in order to make sure you don’t lose precious lean muscle.

How much Weight Loss is Safe?

The amount of weight loss you can safely lose is dependent on how much bodyfat you can metabolize. This is usually higher for persons of a larger body mass and higher body fat levels because their overall metabolism is higher and their body wants to return to a stable bodyweight.

The converse is also true, because persons with a lower body mass and lower body fat levels will find it harder to lose weight that isn’t lean tissue.

A good estimate is to lose around 1% bodyweight per week. You can aim higher, however it is always safer to aim at the lower end of the spectrum. This translates to a 200lb male aiming to lose 2lbs per week.

Check out How Fast Can You Lose a Stone?.

Calculating Daily Calories for Weight Loss

Once you’ve established how much weight you’re aiming to lose per week, you can now calculate your calorie deficit. Subtract 500 calories from your daily calories for every pound you wish to lose per week.

Daily Calories = Maintenance Calories – (500 x weekly weight loss goal)

Step 4 – Adjust your Calorie Deficit

The calories you calculated is only an estimation and in reality it will vary on a daily basis based on several factors:

• Fluctuations in Diet
• Calories burned during Exercise
• Calories burned outside of Exercise

It is very difficult to be precise with your calorie deficit because these factors are difficult to control. Therefore, it is important to track your nutrition and weight regularly in order to ensure that you are experiencing weight loss.

By tracking your nutrition and weight simultaneously, you can simply decrease calorie consumption or increase exercise if you are not experiencing weight loss. That way you will always be on track on your weight loss journey.

Tips for Creating a Calorie Deficit

1. Diet

Diet has been shown to be the easiest factor to control to create a calorie deficit. Consume foods high in fiber and protein in order to keep satiated and keep your hunger cravings at bay. Avoid foods too high in sugar and fats as these can add too much calories to your diet.

2. Exercise

Exercise can help you burn more calories to add to your deficit. Perform cardiovascular exercise as well as resistance training. This will spare and even build lean muscle which will increase your metabolism to burn more calories.

3. Non-Exercise Activity Thermogenesis

Your body is burning calories outside of exercise. That’s why it’s important to become more active. Simple activities such as walking more often can have a big impact on your weight loss.

Follow these tips to create and maintain the calorie deficit that you calculated and you’ll be sure to lose a lot of weight and get the physique of your dreams.

If you’ve figured out your calorie deficit and you’re still not losing weight, check out Why Am I not Losing Weight in a Calorie Deficit?

References:

Abete, I., Parra, M., Zulet, M., & Martínez, J. (2006). Different dietary strategies for weight loss in obesity: Role of energy and macronutrient content. Nutrition Research Reviews, 19(1), 5-17. doi:10.1079/NRR2006112

Trexler, E.T., Smith-Ryan, A.E. & Norton, L.E. Metabolic adaptation to weight loss: implications for the athlete. J Int Soc Sports Nutr 11, 7 (2014).

Catenacci, V., Wyatt, H. The role of physical activity in producing and maintaining weight loss. Nat Rev Endocrinol 3, 518–529 (2007).

Finer, N. Low-Calorie Diets and Sustained Weight Loss. The Obesity Soceity 9(S11), 290S-294S (2012) 

Nick Bellissimo, Tina Akhavan, Effect of Macronutrient Composition on Short-Term Food Intake and Weight Loss, Advances in Nutrition, Volume 6, Issue 3, May 2015, Pages 302S–308S