Not Everyone Needs 2,500 Calories A Day: How to Calculate the Calories YOU Need

Just because your father, boyfriend or best friend can scarf down a cow and 5 bowls of kari at each meal and still remain fabulously slim, doesn’t mean you can. Every individual has different daily calorie requirements, and the recommended daily calorie intake of 2,500 kcal isn’t an umbrella number for you and every other human being who shares the same birthday as you.

Your daily calorie needs very much depends on your body weight, height, age, and physical activity status.  It’s simple logic. If you are physically active, you will need more calories to maintain the energy balance, and if you’re sitting or sleeping 90% of your day, you probably don’t need much.

The problems occur when you miscalculate your calorie intake, thinking you’ve consumed less than your expended energy, and that’s the first step towards obesity.

I’m going to teach you how to calculate just exactly what your daily calorie / energy requirement is, but before we get to that, let’s meet Calvin first.

Calvin (pictured above) is an office executive who hardly hits the gym or running tracks. He weighs 80kg, and is 160cm (1.6m) tall. This year, he turns 26. We’ll be using Calvin as an example on how to calculate your daily calorie requirement.

Step 1. Calculate Your BMI 

< 18.5	Underweight
18.5- 24.9	Normal
25.0- 29.9	Overweight
30.0-34.9	Obese I
35.0-39.9	Obese II
>40.0	Obese III

* Adapted from World Health Organization Global Database on BMI (2004) 

BMI Formula = Weight (kg) / (Height (m) x Height (m))

Calvin’s BMI = 80 / (1.6 x 1.6), which is 31.25 (Obese I)

Step 2. Calculate Your Ideal Weight

Ideal weight formula = Height (m²) x Normal BMI (chosen BMI range= 24)

Ideal weight for Calvin = (1.6 x 1.6) x 24, which is 61.4kg (remember this number, it’ll be used later in Step 3)

Step 3. Calculate Your Basal Metabolic Rate

Basal Metabolic Rate (BMR) is the energy required to maintain a normal body’s metabolic processes such as breathing, maintain the normal body temperature, and food digestion. This amount of the energy is vital for the organs to be fully functioning such as lungs, heart, nervous system, kidney, liver, intestine, and more.

The Harris Benedict Formula is used to calculate human basal metabolism, and the formula looks like this:

Men: 66.47 + [13.75 x (W)] + [5.0 x (H)] – [6.75 x (A)]

Women: 655.1 + [9.56 x (W)] + [1.85 x (H)] – [4.67 x (A)]

Reference
W= Use your ideal body weight (kg), which you calculated earlier in step 2
H= Height (cm)
A= Age

Here’s how we calculated the BMR for Calvin:

66.47+ [13.75 x (61.4)] + [5 x (160)] – [6.75 x (26)] = 1,535

Source: Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA 1918;4(12):370-3.

Step 4. Estimate your calorie requirement each day

The final step in the estimation of your calorie requirement depends on your behavior. Look at the table below and pick the group you’re in based on your activity level. Be honest here otherwise it wouldn’t be accurate:

Types of Physical Activity	Daily Calories Needed
Little / No Exercise	BMR x 1.2
Light Exercise (1-3 times / week)	BMR x 1.37
Moderate Exercise (3-5 times / week)	BMR x 1.55
Heavy Exercise (Almost everyday)	BMR x 1.73
Very Active (Twice per day)	BMR x 1.9

Calvin is an office executive, who sits in front of the computer from 8am to 5pm. The only running he does is between cubicles to attend dreaded meetings, where he’s also sitting down. He leaves home at 6.30am and only comes back at 8pm to avoid the massive traffic jam in the heart of Kuala Lumpur (Read: “I don’t have time to hit the gym and I’m always busy even in the weekends – family breakfast and whatnot”).

So Calvin belongs in the “Little/ No Exercise” group. His daily calorie requirement is:

1,535 (BMR) x 1.2 (Little / No Exercise) = 1,842 Kcal ~ 1,800 Kcal/day

Step 5. Adjust Your Calorie Intake Based on Your Weight Loss / Gain Goals

If Calvin wants to shed 10% of his current body weight, it’ll take him about 3-6 months depending on how much effort he puts in it (strict meal planning / workout routine). The healthy range of weight loss is between 0.5kg – 1kg/week.

He needs to reduce 250-500 Kcal from his daily calorie requirement, which means he’ll get only 1,300 – 1,550 Kcal/day.

We’ll discuss further on how to divide your daily calories requirement for breakfast, lunch, dinner, and snacks in between meals in a future article.

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Did your actual daily calorie requirement surprise you? Was it lower or higher than you expected? Share with us in the comments below or on our Facebook page!

 

Edited by The HealthWorks Team
Contributed by Nurulasyikin M, primary care dietitian at Pusat Perubatan Menara, KL.