How Many Calories Do You Need And Why?

How Many Calories You Actually Need And Why
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1100 calories challenge, 900 calories for 30 days, 500 calories each day to lose 20 kg body weight…

I believe you’ve probably heard of the above propaganda before. Almost all the time, these appeared to be too attractive for someone that desires to weight loss. However, this is how things go wrong later once they started accepting these ‘challenges’.

I know that you want to lose weight and a caloric deficit is the key for weight loss. However, most of the time these amount of calories had cutting out for too much, not even meeting the requirement for your body to works.

Hi, tough soul. I’m Alyssa.

For this blog post, I’ll be talking about how many calories do you need. And what is the healthy option for sustainable weight loss for those that are trying to get in shape by cutting calories. Keep reading!

Getting to Know Your TDEE (Total Daily Energy Expenditure)

To know how much essential energy you are required, you need to know what is TDEE first. The TDEE is the total of how much energy you used throughout the day.

Imagine your body as an energy container that is constantly filling up and emptying. Everytime after you consume calories, it fills up with energy, and while you are fasted, you are depleting your energy.

Energy in, Energy out
The energy in energy out module

You spent the energy on both physical and non-physical activities. Here is the breakdown of how these calories are spent:


Your BMR (Basal Metabolic Rate) is the basic energy you require to survive. Which accumulates up to 60% of your daily calorie intake.

A great metaphor will be those background application that keeps working behind your mobile phone even you did not launch it. When it comes to the human body, the process will be more complicated and more energy-demanding compared with your phone. Those energy is being used to regulate basic body function such as breathing, keeping the heart pumping, blood flow, and keeping organs functioning.

Different people will have Your BMR is mostly determined by you lean mass. Then the other factor will be your weight, gender, height and age. However, even for the one that falls on the extreme, their BMR will still be above 900 kcal.

Your body will really struggle if you eat lesser than your BMR.

So please, no matter how you are eager to lose weight with a low calorie diet, don’t go under these number. If you are not sure of your BMR is, head on this BMR calculator to help you figure out.


About 10% of the energy that you consumed will be used under TEF (thermic effect of food). These are the energy that is involved in the food digestion process. Although this is not so significant among the other ones. These are also non-physical activities that burned passively.

Your TEF will be determined by how much you eat. Unless you did not eat at all for a whole day, then your TEF will be zero. Note that protein-based food requires more energy to digest, therefore those that have more protein in their diet will have a higher TEF.


Here comes the EAT (Exercise Activity Thermogenesis). You might already guess what it means. Yes, it’s the energy that we spent during exercise.

Unlike BMR, the EAT is more controllable by an individual.

Most people think that they could burn a lot of calories by working out harder. However, the reality is that no matter how intense your workout is, your EAT only able to accumulates up to 5-10% of your daily calories. For sedentary folks, they might have less to no EAT throughout the day. Of course, for more physically active individuals, their EAT will be on a highier end.


This is called NEAT (Non-Exercise Activity Thermogenesis), which consists of all the energy spent that is not for exercise purpose.

Let me ask you a question. How much energy do you think is needed for effortless movements such as sitting, shaking the leg, talking, spinning your pen, moving your finger etc?

You might expect it requires just a little. But believe it or not, all of them added up reaching 15-20% of your total calories! This means, as long as you are moving, even in the most insignificant way, you are involving NEAT.

How much you spent on NEAT will based on your lifestyle and habit. A person that prefer taking stairs with those that choose to take lift, a person that love gardening with the one that sitting all the day, their NEAT will be different.

Physical activity and non -physical activity in TDEE
The TDEE consists of both physical and non-physical activities

How Much Is Too Much?

For those that looking for weight loss, obviously, you need to consume lesser than your TDEE. That’s the only way. However, remember that you don’t want to go too much until there aren’t any energy left for you to maintain your basic function. You need to eat below your current TDEE, but above your BMR.

Most people will try to eat extremely low calories to lose weight. However, by decreasing their daily calories just by 20 % and be patient, they could still get the same results.

There is an illustration of how much calories you can ‘sacrifice’ for weight loss, and those that are essential so that you don’t go over it.

TDEE (Total Daily Energy Expenditure)
Your TDEE is the total calories that you need in a day to maintain your weight.

Why Going Too Fast Is Counterproductive

A safe range of calories you can cut down is not more than 20% of your TDEE.

For those that seeking fast results by dramatically cutting down too many calories. The problem is it does not only make you feel terrible. But the side effect of our body trying to cope with these changes also bug us and make things even more complicated.

Results in Yoyo-dieting

This are most commonly seen with those that had going through a restricted diet. This isn’t because you are less self-disciplined or lack determination. It’s the coping nature every human has and it’s hard-wired in our brain.

When our body is lack of something, it will try to ‘communicate’ with your mind to get it. You will not notice it in the first place, but it will slowly develop into excessive hunger or a great desire towards certain food group. Then this will happens. These people ended up stumbling into the rabbit hole of excessive hunger, overeat , feeling guilty, cutting calories again, and then repeating the cycle.

You’ll Get Moody

When someone has a bad temper before their meals, we called it ‘hangry’. This is a real thing. The feeling of irritation, sudden mood swing and low spirit is the results of low blood sugar before meals. After you had a meal, then your blood sugar will back to its normal level and you’ll feel better again.

However, for people that are eating too less, their blood sugar will remains at a low level all the time. People experience some degree of psychological effects due to the deficiency of nutrition. Imagine these happen all the time for those people that are in long-term starvation. In long term, these grumpy feelings might no longer appear as some random emotion but could affect your mental health such as depression or anxiety. Well, not fun at all.

You’ll Experience Some Physical Side Effects

Remember that we need enough energy to support the bodily function in you BMR?

Human body has its own way of working and it’s top priority is to keep you living. When you are eating too less and is under your BMR, it lacks the essential energy for it two maintain your bodily function.

Of course, as I mentioned above, it will seek out the ‘storage’ first before tapping into different kinds of side effects that we hate. However, there is a limit. Once your body thinks that this solution doesn’t work for the long term, it needs to seek out another way.

It will conserve those energies for the function that is more important for survival. You feel lethargic. You’ll notice your skin becomes dry and looks terrible. You feel cold all the time,because your body stops using energy to keep you warm. Not to mention other effects as well.

It Affects Your Metabolism

When your body is in deficiency, the other strategy it uses is to break down your lean mass to conserve more energy. As our BMR is determined by your lean mass, therefore if you have
Therefore you might be joyed when you notice weight loss, but the reality is that you might possibly be losing your lean mass instead of fat mass.

If you had read my post about body composition, you’ll know this isn’t a good thing. When you lose your lean mass, at the same time also means that you are losing muscle mass. The less muscle you have, you will have a lower metabolism. This is because muscle is highly energy demand, and by losing it, your body can effectively ‘save the cost’.

Final Thought

I hope this post give you a better overview of how our energy is being optimised. For this, you can acknowledge the importance of the essential calories that we need. Calories is not your enemy.

Human body is complex. Sometimes we think we can fully control it, but in fact, we can’t. Sometimes the best way to make changes is to take things slow. Although it takes longer time, but the results will be more sustainable and you’ll suffered less during the process.

Let us grow together,


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