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The science behind losing weight

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Everybody knows you need to eat less and exercise more if you want to lose weight. However, many still struggle to lose significant weight after weeks of trying, making them wonder whether they are doing something wrong and why is it that some people manage to lose weight so easily!


In this article, we will make you properly understand how the body gains and loses weight and so you can adapt your programme to be more effective.


It's all about energy

We all learnt in primary school that energy cannot be created nor destroyed, only transferred from one form to another. This is also true for our body. Our body is like an engine that needs energy to do work. An engine gets its energy from fuel such as petrol or diesel, and uses that energy, converting it, into kinetic energy to move the wheels of your car. Your body gets its energy from food, and uses that energy, converting it, so you can do various activities like walking, thinking or just staying alive.


If we eat too much food, that means we are giving our body more energy than it requires to enable us to walk, to think, to stay alive, etc. This extra energy will be stored and the storing of this energy is the source of weight gain.


On the other hand, if we do not eat enough food, the body will go to our energy store to cover for the deficit and the reduction of this storage will result to weight loss.


So it's simple: put too much energy into your system and the body will store it and you will gain weight. Put too little and the body will use the energy store and you will lose weight.





This means there're two things you can do to force the body to use this energy store: input less energy than the body requires or make the body work harder so it requires more energy than you put in. You can achieve the former by going on a diet and the latter by being more active!


Your new best friend: calories

You've all heard of 'calories'. You've probably even used it, maybe without actually knowing what it means [cue angry English teacher]: "oh that's so little calories, it's great!", "oh that's so many calories, it’ll make you fat!" But what is it exactly?










In the previous section, we talked about energy. We said the body requires energy to do work and stores the extra energy it doesn't need. But how much energy does our body requires and how much energy do we eat and how much weight do we gain from the storage of energy? This is where calories come in.


Calorie is a unit of energy. 1 calorie is equal to 4.184 Joules of energy. Most food comes with thousands of calories so we normally talk in kilocalories which is 1000 calories or 1 Calorie (note the capital ‘C’ NOT a small ‘c’). It's worth making this absolutely clear as there seems to be quite a lot of misunderstanding out there: 1 Calorie = 1 kilocalories = 1000 calories. Calorie is often abbreviated to 'Cal', calorie abbreviated to 'cal' and kilocalories abbreviated to 'kcal'. For the rest of this article, we will stick with 'kcal'.




So let's get down to the numbers, how much energy does our body requires in each day? It depends. Every human being is built differently and we all do different activities. For example a male human will burn more energy than a female doing the same work. A construction worker will use more energy than a taxi driver. We split up this energy usage into 2 parts: the ‘resting’ energy and the ‘activity’ energy. The idea is in one day, if you simply just woke up and lied in bed all day and went to bed, all you are doing is just staying alive, you are not doing any extra activity on top. The body already requires a certain amount of energy, to breathe, to activate the brain, the heart, etc. This ‘resting’ energy is called the Basal Metabolic Rate or BMR. It depends on each person’s metabolism, how big your body is, how well your internal systems function, how you are built, what your chemical levels are like, etc. It depends on quite a lot of things! Fortunately, someone came up an easy approximation to this number while factoring in only the easy parameters that we can easily obtain like your height, your weight, your age and your sex. ​To calculate what your BMR roughly is, try googling 'BMR calculator' and give it a go!


For the purpose of this article, let's say you are a healthy female, in reasonable shape, you may have a BMR of 1,300 kcal per day. On top of this, you will be burning energy to do your daily activities like brushing your teeth, eating, walking, working, etc. This also varies person by person but again, someone came up with a few 'norms' that most people will fall into e.g. in each day you commute to work at a desk job and don’t do any extra workout, you will be classified as ‘inactive’, or perhaps you are reasonably active: your job requires a lot of walking, thinking, and you exercise a couple of times per week. Again, you can easily get an approximate number from the Internet.


Let's say you are classified as inactive, you may probably be burning around 300 kcal per day on top of your BMR. Add this up with your BMR, this means in each day, you require 1,600 kcal to go about your daily life.




So, if you eat more than 1,600 kcal per day, your body will store that excess energy and you will gain weight. If you consume less than 1,600 kcal, you will force the body to use the reserve, and you will lose weight. It’s as simple as that!


The next question many calories do I eat per day? Again, this depends on a lot of things: how much fat do you eat, do you use cooking oil, what kinds of meat are you eating, etc. But again, in the modern world of health awareness, someone has already taken the time to measure the energy in most types of food we eat so you can simply google the name of the dish you are having, adding the word 'calories' and you will most likely find it. For products in the supermarket, you will most likely find this number on the packaging.


















So let's say, your diet is mainstream: perhaps a bowl of cereal in the morning, an ordinary meal in the afternoon and dinner. On top of that, you might have some small snacks between the day and a cup of coffee. This doesn't sound like an unusually ‘fat’ diet at all but surprisingly if you are eating like this, you can be putting in around 2,000 kcal into your body! This is 400 kcal more than your body burns so your body stores this and you will gain weight, everyday!


The next question much weight does this 400 kcal translate to? This one is simple: 3,500 kcal = 1 pound = 0.454 kg. So 400 kcal equates to 52 g which isn't very much. But if you have been doing this for weeks, months, years, then...the 52 g adds up to quite a few kgs! Note: you will not actually gain 52 g everyday because once your weight increases, your BMR will also increase, making your excess energy smaller and hence the weight you gain is slightly less than 52 g. This means your weight actually increases asymptotically rather than linearly. The same goes for losing weight. Bottom line is if you use this calculation, you will reach your target slightly slower than expected.




Now in the opposite direction, if you want to lose weight, let’s say 2 kg in 4 weeks’ time, you would need to save in total approximately 15,400 kcal in 28 days. This means saving around 550 kcal per day. So for our imaginary woman who burns 1,600 kcal per day, this would mean she would need to cap her energy intake to 1,050 kcal per day. So if she has been eating 2,000 kcal per day, she would need to halve her diet!


This may seem like a tough task…and this is why when you google ‘lose weight’, you see articles about eating and you also see articles about exercising! Exercising can also help you lose weight because it increases your energy requirement. Maybe you feel cutting your diet in half seems like an impossible task but perhaps reducing it by 25% to 1,500 kcal is doable. And let’s say you want to achieve the same goal: lose 2 kg in 4 weeks’ time. So again, you would need to save 550 kcal per day, so you would need to increase your energy usage so that it is 550 kcal more than the 1,500 kcal you aim to eat, so that’s 2,050 kcal. So for our imaginary woman who burns 1,600 kcal per day, she would need to burn an extra 450 kcal.


















Again, the Internet is your friend if you want to find out what kind of exercises burn 450 kcal and again these numbers do vary for different people. But for an average person, 450 kcal can be burnt by jogging for around 1:15 hours. Maybe cutting your diet in half doesn’t seem that impossible after all eh?


Inaccuracies…welcome to the world of science

You might be shouting... “but I do eat 2,000 kcal everyday and I don't gain any weight!” and yes you may be right! This is due to the inaccuracy of calculating approximates like the BMR, which only uses weight, height, age and sex whereas the actual calculation depends on so much more than that e.g. whether some particular enzyme is working properly in your body, whether a certain chemical is at the correct level, what your muscle-fat ratio is, etc. You would need to undergo various tests at a hospital to accurately calculate your specific BMR. Worse is, it could change everyday because, like we said, as you lose weight, your BMR reduces, where you are, what you eat, how you are feeling, can all affect your internal systems.


Another inaccuracy could come from the 300 kcal on top of the BMR. For example, everybody has a different brain: perhaps you need 100 kcal to completely read and understand this article whereas one of your friends may require 200 kcal, or, the fact that each person does not digest food the same way: some people may only be able to extract 80% of the calories they consume and the rest is excreted, or some people may only be able to use 50% of the calories they digest and the rest gets stored straightaway.


So actually, calories may not be that useful after all…

These inaccuracies may make the science behind losing and gaining weight seem like a black art…but nevertheless the concept of energy transfer isn’t. So although you may not be able to accurately say how many calories your body requires in each day or how many calories you are eating, you can still use the concept of energy imbalance to lose weight i.e. eat less than what you burn.


















​If the calories calculation doesn’t seem to add up in your case, you could simply start with a lifestyle that doesn’t change your weight. This will be your base case. If you eat less than this or burn more energy, you WILL lose weight. (You can also obtain the amount of energy you burn each day by calculating the amount of calories you eat since the body has to burn all that energy if your weight stays constant) Losing weight this way won’t require you to keep track of your calories and allows you to not be stressed out by everything you eat. The cost is you will not being able to quantify the weight loss or time frame needed. One thing you may need to keep in mind is that, you will burn less energy as your weight reduces, so you may need to keep reducing your calorie intake or further increase your energy usage as you get slimmer and slimmer.


The satiety/calorie ratio

Now that we’ve established the energy side of losing weight, we turn our attention to another aspect: satiety. 1 calorie isn’t the same for all types of food in terms of satiety.


The top reason why people fail on a diet is simply because they can’t withstand the feeling of hunger during the day. So the goal for a diet, isn’t simply just to go down to your calorie target, but also getting there without feeling tortured!

















If you have a quota of 1,000 kcal per day, you need to fill that with the most filling foods. To put that into perspective, your 1,000 kcal quota can be filled with 7 cans of soda or 7 kg of lettuce! Obviously, the lettuce is going to make you feel much more full in a day than 7 cans of soda. In fact, it will probably make you feel full for much longer than that! So it’s not about just going for food with low calories, you need to take into account what kinds of food make you feel full as well. As a general rule of thumb: sugars and fats, per calorie, are poorer at filling your stomach than proteins and carbs. The best is fibres! This is one of the reasons why cola isn’t on anyone’s diet list but vegetables and fruits are on everyone’s.




Determination is key

We have covered quite a lot of basics in this article but there is a lot more to study if you have more time. For example, we haven’t even touched about your body fat composition and how it creates the different phases in losing weight. Nevertheless, this article should enable you to achieve reasonable weight loss and I hope it has been useful to you.


















Now that you have the science behind the basics of losing weight, all you need now is determination! Arguably, this is the most important aspect in losing weight. In fact, it’s probably the most important aspect in anything you do in life. As the old saying goes: no pain, no gain! You’re bound to feel uncomfortable at times but…if get your science right, and you keep fighting, then for sure any goal you set will be achievable!