I Wanted to Know the Truth About Carbs. Here It Is

Auriane Alix
I look at food with a very different eye now…
Photo by Mae Mu on Unsplash

Are carbohydrates responsible for fat gain? Yes and no. That’s the complexity of the matter. Let’s stop with the false assumptions and shortcuts. The reality is not so difficult to understand. It’s actually quite simple.

We make nutritional choices based on what we’re told, without ever making the effort to understand how these foods affect our body. Yet, food is our fuel.

For a long time, I just ate what I wanted to eat. I was told that fruits and vegetables were better for my health than hamburgers and pastries, so I tried to eat more of the former than the latter. It wasn’t until I began to realize the crucial importance of diet, and started my fitness journey, that I became interested in nutrition.

I wanted and needed to know what I was putting into my body. Which choices were to be preferred. What false beliefs had been guiding my diet for years.

Starting with carbohydrates. Most people misunderstand them. Most explanations on the subject make it more complicated than it is.

Here’s a digest of the ton of reading I’ve done.

If you are on a fitness or weight loss journey, this is for you. Welcome also if you just want to understand your body.

Carbohydrates are necessary for your body and essential for your brain

Carbohydrates are found in many foods. The most common are fruit, milk, chocolate, cakes, bread, rice, or pasta. Carbs are divided into two categories:

  • Simple carbohydrates
  • Complex carbohydrates

Your body needs carbs. Opting for a carbohydrate-free diet is a very bad idea. Carbohydrates are a major source of energy for the human body. Together with proteins and fats, they are one of the three macro-nutrients that are essential for the proper functioning of your body.

It’s also the only source of energy for the brain which, unlike the rest of the human body, cannot draw on fat to function. We will come back to this later.

Simple carbs

They are made up of 1 or 2 molecules and are therefore metabolized very quickly. Simple carbohydrates are mainly made up of sugar: glucose, fructose, and saccharose.

Fruits, fruit juices, milk, yogurt, pastries, chocolate, jam, and maple syrup are some examples of simple carbohydrates.

Complex carbs

They are composed of a large chain of molecules and have to be divided into several small molecules to be absorbed by the body, which slows down the process.

“Complex carbs pack in more nutrients than simple carbs. They’re higher in fiber and digest more slowly. This also makes them more filling, which means they’re a good option for weight control.” Healthline

Bread, pasta, rice, cereals, legumes, and potatoes are complex carbohydrates.


Yes, you need carbs.

No, complex carbohydrates are not particularly better than simple carbohydrates for weight control. It’s a little more complicated than that.

Let’s continue.

Your body is a carbohydrate processing machine

When you eat carbs, whether simple or complex, your body turns them into glucose.

“Glucose comes from the Greek word for “sweet.” It’s a type of sugar you get from foods you eat, and your body uses it for energy. As it travels through your bloodstream to your cells, it’s called blood glucose or blood sugar.” WebMD

Glucose is then distributed throughout the body for use by cells, especially nerve cells. It is the brain’s only source of energy: it consumes an average of 5 grams of glucose per hour. This is why it’s important to keep your carbohydrate intake above a certain threshold.

This brings us to blood sugar: the level of glucose in the blood.

Carbohydrates are classified according to the Glycemic Index

“The glycemic index is a value assigned to foods based on how slowly or how quickly those foods cause increases in blood glucose levels. Foods low on the glycemic index (GI) scale tend to release glucose slowly and steadily. Foods high on the glycemic index release glucose rapidly.” Harvard Medical School

Some foods cause a very rapid and very large increase in blood sugar levels. These are those with a high glycemic index, and the ones that should be avoided to limit weight gain, as we will explain in a moment.

Here is a small table with the main foods:

Image: The Unconventional Dietetician

Simple carbs often raise blood sugar levels faster than complex carbs. But other factors come into play.

There is one problem, however: according to the GI, watermelon, wholemeal bread, bananas and grapes should be avoided. However, fruits are recommended for a healthy and balanced diet. So are wholegrain cereals, which, although they should be eaten in moderation because of their high-calorie content, are still much more nutritious than white cereals. However, according to the glycemic index, the two would be equivalent.

These are the limits of the glycemic index scale. That’s why we use a more precise tool.

A much more precise scale: the glycemic load

The glycemic index of a food item alone is not enough to determine the impact of that food on glucose levels. The amount of carbohydrates present in the food must also be taken into account. This is why nutritionists use a second parameter, which is the glycemic load (GL).

This is the case with fruit, for example, their glycaemic index is certainly high. But they are mainly composed of water. With the same glycemic index, they cannot raise glucose levels as much as a food item containing more carbohydrates.

The results between the glycaemic index and glycaemic load are very different for the same food. Here are a few examples:

  • Watermelon: GI = 65 / GL = 4
  • Pineapple: GI = 59 / GL = 7
  • Banana: GI = 52 / GL = 11
  • Wholemeat bread: GI = 50 / GL = 24


Choose your food according to its glycemic load, not its glycemic index. By choosing foods with a low glycemic load, you regulate your blood sugar level and therefore avoid too much action by the hormone responsible for weight gain: insulin.

Insulin pleads guilty

It’s all very nice. We have understood the role of carbohydrates, how they are classified, and which ones should be favored. But it’s time to find out why. Why is it said that carbs are responsible for weight gain?

The answer lies in one word: insulin.

“Insulin is a hormone made in your pancreas, a gland located behind your stomach. It allows your body to use glucose for energy.” Healthline

When we digest carbohydrates, the pancreas immediately produces insulin to allow the cells to use the glucose and prevent it from staying in the bloodstream in too large a quantity.

When the blood sugar level rises a little too much as a result of consuming sugar-rich products, the insulin is responsible for transporting this excess sugar to the reserves, where it is stored.

There are 3 reserves :

  • Muscle tissue
  • Liver
  • Adipose tissue (fat)

The first two reserves are quickly saturated. Insulin, therefore, transports the excess carbohydrates, already transformed into glucose at this stage, to the adipose tissue, where they are stored as fat.

This is why it is often said that carbohydrates make you gain weight. This is both true and false since it is only the excess of poorly chosen carbohydrates that becomes converted into fat.

In summary

Contrary to many beliefs, it is by no means the consumption high-fat foods that leads to the appearance of physical fat. It is the excessive consumption of carbohydrates with a too high glycaemic index and glycaemic load that causes a spike in blood sugar, forcing insulin to convert these carbs into fat.

For example, in their Glycemic Index experiment, Professors David Jenkins and Thomas M.S. Wolever found that consumption of grain products such as white bread caused a phenomenal rise in blood sugar levels, as high as consumption of pure sugar.

Foods with a low glycemic index, which therefore lead to virtually no weight gain, are often raw or natural foods that our bodies know and recognize and therefore know how to use. They are products of nature.

Also, the more a food is cooked, the higher its glycemic index increases.

It is essential to maintain a supply of carbohydrates in your diet. Carbs must simply be well chosen and eaten in moderation, alongside a majority of unprocessed, natural foods.

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