Do you know when exactly the body stores fat? And what’s the main driver behind fat storage? Is it carbs fat or maybe even protein?

 

In this post, you will learn everything you need to know about the science behind weight gain.

 

A few years ago it was fat. Today it’s usually carbs or sometimes even protein. The diet industry and our media always seem to have a new culprit for weight gain and obesity.

 

They will tell you that eating anything high in fat will automatically make you gain fat and therefore you should avoid everything from fatty stakes to nuts to whole milk. Or they might say that sugar is the real reason obesity rates have spiked over the last decades and that’s why we need to implement a sugar tax.

 

Listening to all this contradiction information probably has you confused about how the human body actually stores body fat, and what really makes us become fat.

 

Today I want to clarify the basic process behind fat storage and answer the most common questions on weight gain. As you will see in a minute, even though the underlying mechanisms are fairly straightforward, there is a lot you might misunderstand.

 

 

 

At its most basic level, fat storage comes down to higher energy intakes than energy expenditures. What this means is that, if we exclude changes in water retention and hormone levels, you have to consume more calories than your body burns to get fatter.

 

Why?

 

Like all living organisms, the human body runs on energy. In a closed system like our body, energy can only be transformed but it cannot be created or destroyed.

 

What this means is unless you overeat, your body doesn’t create energy out of nothing and you have to get the necessary energy from somewhere to grow your fat cells. This ‘somewhere’ is normally food, which is the main provider of energy in the form of calories.

 

Pretty much all studies on weight changes support this, and the ones that don’t usually asked participants about their food intake and only strictly monitored their weight. As you might know, most people are horrible at remembering what they ate and even worse at estimating their calorie intake.

 

When you eliminate these reporting mistakes and also strictly monitor food intake, studies always find that calories are the main driver of body fat changes and that overeating is the real problem. I’m not saying this to bash on the overweight.

 

In fact, most people overeat unconsciously and pretty much no one gets fat on purpose. My point is simply that unless you create a calorie surplus you won’t gain body fat.

 

Once you understand the importance of calories you probably want to know how many calories lead to how much weight gain. This is a difficult question to answer in absolutes.

 

A common notion is that one pound of fat stores 3500 calories, so eating 3500 calories above maintenance will lead to one additional pound of body and eating 3500 calories below maintenance will make you lose one pound. 

 

While I think this idea is helpful when setting up diet plan especially when you are a complete beginner, it ignores how different metabolisms, hormones and a lot of other important factors vary from one person to the other.

 

Studies have shown that overfeeding people of the same age and weight can lead to drastically different outcomes, especially when this is done within a short timeframe. So, even though I cannot tell you exactly how many calories you need to overeat to gain a pound of fat, we know the main driver of gaining that pound of fat are calories and nothing else.

 

Now that we covered calories, let’s talk about the exciting stuff: fat, carbs and protein.

 

 

 

For this, you have to understand the basic roles of each. Carbs and fat are primarily used for energy, whereas protein is mostly used to build and repair tissue. 

 

To ensure a consistent reserve of energy the body stores carbs as glycogen (mostly in the muscle and liver) and dietary fat in fat cells. There is no real storage of protein. So when the body needs to draw on energy reserves for exercise or just simple movements, in theory, it can use either stored carbs or stored fat.

 

In practice, your body will always use both to some degree, but one will usually outweigh the other. For example, at rest, the body burns primarily fat and only little glycogen, but the percentages shift to more glycogen and less fat the more intense you exercise.

 

But what happens when you provide your body with more energy than it needs? That is, what happens when you overeat on carbs or fat?

 

Let’s assume you have a fairly balanced diet and start overeating on only one macronutrient, while also creating a calorie surplus (which as we know is the underlying condition for weight gain). Will overeating on carbs and fat both lead to weight gain?

 

Yes, but in different ways.

 

The case of fat is fairly simple. If you overeat on dietary fat the additional energy is mostly stored directly in the fat cells. For carbs, it’s a little different. When you eat more of them, your body will take advantage of that and use more carbs for energy and less fat for energy.

 

Understanding this hopefully explains why both scenarios will lead to the same results.

 

In the first, your body will simply store more fat because you are eating more fat. But in the second your body will also store more fat. Not because you eat more of it but because the additional carbs mean your means needs to burn less fat for energy and can store more of it.

 

Many people misunderstand this and therefore propagate certain low fat or low carb diets because they think the additional macronutrients and not the additional energy in the form of calories are to be blamed for weight gain.

 

 

 

The body can actually turn protein into carbs and use it as an alternative energy source through a process called neoglucogenesis. If you overeat on protein and the body had no use for the extra protein (for example to build muscle tissue), it would start burning more of it for energy.

 

This, in turn, means it would need fewer carbs and less fat for energy, which means a bigger percentage of them will get stored. Now I at this point should mention that the average person usually overeats either on processed carbs or on fat and doesn’t get enough protein. So even though you can gain fat by overeating on protein, it’s not as common.

 

 

 

After hearing all this you are probably wondering whether a no fat diet would be the way to go. If only dietary fat get’s stored as body fat why not deprive the body of it and eat as much protein and carbs as you want. Unfortunately, this isn’t possible either.

 

Not only do you need a certain amount of fat in your diet for hormone production and vitamin absorption. Your body can also store carbs as fat when dietary fat intake isn’t high enough. This is called De novo lipogenesis and your body does it when you are consuming a high amount of calories without providing a lot of dietary fat (usually less than 10% of all calories).

 

So the bottom line is that you would still get fat.

 

 

 

Excess calories for a prolonged amount of time always cause fat storage no matter what you eat. Our bodies are extremely intelligent and had to be able to store energy from all kinds of foods, otherwise we would have died out a long time ago.