Calories. Do they matter?

In simple terms, no.

The module of calories in, calories out (CICO) is based in the first law thermodynamics that dictates that energy cannot be created or destroyed. Translating that into calories and body energy, the calories you eat have to be either used or stored. And if you do not use them, the alternative will make you fat. To a certain extent this is true, albeit, an oversimplification.

But consider this: If all we need to do is to ensure we spend more calories than we consume why is that the majority of the population is getting bigger?
Are they all lazy slobs that can't be asked to work out? If the dietary guidelines provided by the government, dietitians and doctors are to eat less fat, why is diabetes on the increase?

I'm guilty of thinking this from time to time. Until my trips to the gym stopped showing the results I expected and I ended up losing 3 times more weight in 9 months by changing my diet than in my entire gym life.

There's actually several reasons why calories don't matter as much or at all.

  • Not all calories are the same:
There's roughly 9kcal per gram of fat and 4kcal per gram of carbohydrates and protein. I say roughly because the actual amount will depend on many factors like the individual food items and cooking. But let's assume that they are fixed values.
Logically we will be better with eating less fat and more carbohydrates. Because a calorie is a calorie, correct?
Wrong! 1g of sugar does not equal 1g of beef, even though they will provide you with roughly the same 4kcal. Plus fat, though calorie dense, is more satiating. So if you have to eat double the carbs for you to feel full, you are no better off. Let alone the other nutrientes lost or lacking in many carbohydrates. Fat is also responsible for the production of leptin, an hormone that, among other things, tells your body when you're full.

  • Not all calories are treated the same way:
Despite the calories not being the same, they are also not treated the same way.
If you consume carbs, you are giving your body a form of energy that your body has limited storage for, can't have too much of floating around and is ready to be used. Calories from fat will be from this point on their way to the warehouse. And if your carbs consumption is too high, some of these carbs will also be converted into fat. Yes, you can try to burn them all. But can you burn your entire meal before the next one? You can't outrun a bad diet.

  • Metabolically adaptation:
Your body is very clever in adapting. Have you ever count calories? I bet you have. I did. Did it work? Well, in the beginning yes. Did the weight come back? I bet it did. And for many people it came back twofold.
If you restrict your body of calories your body will eventually learn that calories income is low and will amend calorie expenditure accordingly. That is what happened in the US TV show The Biggest Loser. Dr. Jason Fung also explains it in his blog.

Imagine your usual intake is 2000kcal. And then you reduce it to 1000kcal. You expect your body to use 1000kcal from your fat reserves, right? Well, your body has evolved to always keep a backup plan and you're undermining it. So in the first few days or weeks, sure, your body will use the reserves but then it will adapt to only expend just as many calories in order to preserve your fat stores. Who knows what harsh times are ahead? For all you know, the reason your eating less is because food is scarce. Best to have fat stored.
Your body will force certain areas to consume less energy, eventually matching the energy expenditure to the incoming energy. For example you can feel more cold.
Just like your pay check at the end of the month. If you get £2000 every month and are used to spend it all, maybe because you have some nice savings to fall back to , and suddenly your boss cuts your salary by half, you will use your savings until you make the necessary adjustments to only spend £1000 (or find another job) in order to preserve your savings.

The interesting thing is that the contrary also happens.
If you consume extra calories, your body will eventually increase expenditure. You will see bursts of energy. In the beginning, you may get fatter as the body will see an excess of energy so it will bump its stores while it gets adapted, just like it has evolved to do. Eventually it will level out and force cells to use more. For example brown fat cells use/waste energy for heat.
It's probably worth mentioning that if you're on a low carb diet and your body can easily access your fat reserves, the increase in calories won't necessary translate in an increase in fat storage, unless these reserves are very low. Ketones promote white fat cells to behave like brown fat cells and these consume more energy even on stand-by. So the result is, more fat on a low carb, after being fat adapted, usually equals to increase in energy only.
Applying the money analogy, the first few months you get a pay increase, you may chose to bump your savings up, if savings is important to you,  for a rainy day. Eventually your outcomes will go up as well because you have no need to keep saving it if your savings are already healthy. Get yourself a new car.

  • Insulin - the traffic cop:
Wait! So why do people get fat? Well the reason is not directly linked to an excess calories. Though fad diets will play with your hormones and mess up your body signals to the point that you may be hungry all the time.
The reason, for the majority in this day and age, is to do with insulin.
The presence of insulin will dictate when the body allows the fat stores to be used. And the current guidelines advise you to eat low fat, high carb and often.

When we eat, insulin is sent out to help with energy allocation. The amount of insulin required is linked to glucose (carbohydrates) and also protein. But protein has a lower impact than carbohydrates. Fat effect on insulin is very minimal. The job of insulin is to tell cells to use the glucose present and to keep the fat locked away. Any extra fat will be also put away as a result. 

When the insulin is low, the body takes energy from fat. This happens when you fast, when you sleep and when you don't eat carbohydrates or too much protein.
Before the fanfare of the low fat brigade and the food industry trying to force feed you sugars, crisps and sandwiches every hour of the day, we used to go hours in between meal. And all this on top of having a more laborious job and commutes. The current advice only causes insulin to stay high constantly.

In other words, the reason most people get morbidly obese is due to metabolic syndrome, or insulin resistance, which is when cells stop answering to insulin. In simple terms, the constant and high consumption of sugars and starches, made even worse by low fat, have made them insulin resistant, in that the body needs to use more insulin to do the same job it used to do with a lot less. This cause the insulin to be present in the blood stream for longer, the fat reserves to be inaccessible and eventually fat stores to not even be able to take anymore fat. It's a vicious circle.

So, calories matter matter?
In one way yes, but in so many others no.
The important thing to take note is that your metabolic rate is affected by what you eat and when you eat, not just how much you eat.
Insulin and the amount of carbohydrates you eat play a role and so does the periods you don't eat, either fasting or simply in between meals.
Snacking will hinder your process and so will eating a restricted calorie diet. Exercise helps but not to the extent anyone will make you believe. Exercise will impact your metabolic rate by a small margin. On top of this each body is different. Your body is constantly trying to maintain homeostasis.
In sum, eat real foods, eat low carb, eat high healthy fat, eat when hungry and stop when full.