How Many Calories Do I Need?

by Dean McKillop 6116 views Nutrition

How Many Calories Do I Need?

Calories... What are they? Calories are simply a measurement of the amount of energy that is provided by the consumption of the food we eat and also the amount of energy burned to help facilitate numerous functions of the body both internally (organs, thermoregulation, metabolism of food) and externally  (day to day activity, specified exercise).

How do we do determine how many calories we need?

Let's look at some important definitions first:
BMR/RMR (40-70% of daily calorie requirements)

BMR – Basal Metabolic Rate

Refers to the amount of calories required to maintain physiological function, including but not limited to the function of your vital organs, your general metabolic function and cell regeneration. BMR is also directly related to your age, whether you are male or female and your lean body mass or how much muscle you have.

BMR is measured in a metabolic chamber after a phase of complete fasting overnight and is extremely stringent in its approach to the scientific collection of its data.

RMR – Resting Metabolic Rate

RMR is essentially the same measurement of BMR, however, the testing protocols for determining the calorie requirements are less stringent, whereby the scientific collection of data is taken in a more normalised environment for the individual, whereby they still fast but are able to sleep in their own home and then travel to the lab for testing prior to consuming their first meal.

Generally speaking RMR results in a 10% higher reading then BMR for calorie requirements to maintain normalised metabolic function.

NEAT

travelling to work

Non-Exercise Activity Thermogenesis (NEAT) refers to a number of calories burned from general day-to-day activity that does not come from direct or specific exercise. Things like your activity around the home, your travel to and from work and anything that implies activity without directly being referenced as exercise is considered NEAT.

NEAT is one of the major fluctuating determinants of calorie requirements and is hugely affected when dieting as individuals tend to reduce their NEAT when eating less, but we will discuss this in another article later on.

TEF

The Thermic Effect of Food (TEF - 10% of daily calorie requirements)) refers to the increase in bodily temperature as a direct result of the breakdown and assimilation of the food consumed in your diet.

TEF despite being important can generally not be manipulated as a factor of calorie consumption and is generally not used in the consideration of daily calorie requirements.

PAL

Physical Activity Level is one of the major contributors to daily calorie requirements outside of your RMR and is accounted for by the calories you burn due to direct exercise.

Depending on your PAL and its intensity, it can require up to a 20% to 100% increase in RMR calories to ensure calorie maintenance is achieved.

TDEE

Total Daily Energy Expenditure (TDEE) refers to the amount of calories required for calorie maintenance, whereby consumption matches exertion and it factors in the individuals RMR, TEF, NEAT and PAL in order to provide the most accurate measurement for determining your calorie requirements.

Matching your TDEE with your consumption of calories will result in weight maintenance, eating less will result in weight loss and conversely eating more will result in weight gain.

Making it simple

So now that we understand all of the factors that contribute to your TDEE, we can look at estimating how many calories you need to achieve the goal you are after.

But seeing as though not everyone loves maths and formulas, I am going to make this easy for you by paraphrasing the work of Lyle McDonald and his recommendations on finding your calorie maintenance in the fastest and simplest way possible:


If you are female:
 

Multiply your body weight in pounds by 14 (kcal)

70kg female (70x2.2 to get pounds) = 154lbs

154lbs x 14 = 2156kCal

If you are male:
 

Multiply your body weight in pounds by 16 (kcal)

90kg male (90x2.2 to get pounds) = 198lbs

198lbs x 16 = 3168kcal


Pretty simple!

Well maybe too simple as there are some metabolic variations in different populations, however, it is a great start. Once you have this baseline number, utilise the 'fudge factor' rule to individualise your calorie requirements by increasing or decreasing them by 5-10% either way.

Final Notes

So now that you have a better understanding of calories, what they are and how they are determined, you can use this information to set up your daily calorie target for weight maintenance, fat loss or muscle gain.

By understanding that the number 1 determinant for weight gain, maintenance or loss is the calories you consume, calculating what your maintenance requirements are will allow you to ensure you are eating the right amount of calories to achieve your goal with minimal negative effects as possible.

weight maintenance

Secondary to this, it is then important to ensure you are eating the right amount of macronutrients (protein, carbs, fats) so keep an eye out for an article on that where I explain the benefits of each macronutrient and how much you should be aiming to consume each day. 

Dean McKillop

Exercise Scientist

I completed my Exercise Science Degree at the University of QLD and have worked in the fitness industry for over 8 years, including a short stint at the Brisbane Broncos in 2010 as a student. I also hold my Level 2 Strength and Conditioning Coach accreditation (ASCA) and have competed in 1 bodybuilding season, placing 2nd at the IFBB u85kg Nationals.

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