Do carbs make you gain weight? Separating fact from fiction

Through diet culture, social media, and film and television shows, we have been given the message that carbs are unhealthy and lead to weight gain.

For many people, they have become a villain in health and wellness, and many try to avoid them as much as possible in their daily food intake. But like a lot of things we see online, it's not exactly that simple.

Carbohydrates are an important part of a healthy diet and provide important fuel for our minds and bodies. However, there are some factors to be aware of when consuming certain types of carbs, and people with some medical conditions do need to watch their carbohydrate intake.

So, can carbohydrates make you gain weight? Let's find out.

What are carbs?

Before we start digging into the potential link between carbohydrate intake and weight gain, let's make sure we understand what carbohydrates actually are.

Along with fats and proteins, carbohydrates are 1 of the 3 key macronutrients found in our food. Carbs are used for energy and are our body's main fuel source, meaning they help our brain, muscles, digestive system and immune system to function [1].

Carbohydrates are naturally found in many healthy foods such as fruit, vegetables, legumes and grains (such as bread, rice, oats and pasta). They are also found in dairy products and in sugary foods.

There are 3 main types of carbohydrates: dietary fibre, starch, and sugar [1]. Many foods naturally contain a combination of these types of carbohydrates, and some also contain fat and protein.

Foods high in fibre include legumes, whole grains (like brown rice or quinoa) and fruit and vegetables. Starches include potatoes and some other vegetables, grains like rice and bread, and legumes like lentils and chickpeas. Sugars can be found naturally in some types of food (such as fruit) while other types of food (such as lollies, table sugar or baked sweet treats) contain added sugar.

As you can probably guess, not all carbs are the same, and some are considered healthier than others. This is often down to whether they are considered simple carbs or complex carbs, the glycemic index and how the carbohydrates are broken down in the body [2].

The glycemic index ranks foods according to how quickly they raise your blood glucose or blood sugar levels. High GI carbs, or refined carbs, include grains like white bread and pasta, potatoes, sweet treats, most cereals, and some types of fruit.

Low GI carbs include legumes, green vegetables, oats and quinoa, and these encourage a slow and steady release. Being high GI or low GI does not automatically make a food healthy or unhealthy, but it is useful to be aware of.

Understanding the glycemic index is particularly important for people who have certain conditions and need to monitor their blood sugar. These people may need to watch their daily carbohydrate intake, but for most of us, this is not necessary.

Do carbs make you gain weight?

While low-carb diets like the Atkins or Keto diet have been popular for years, this does not mean they are the best or only way to lose weight, nor does it mean that eating carbs makes you gain weight.  

One reason that people claim dietary carbohydrates can lead to weight gain is to do with blood sugar and insulin spikes, which can happen after you eat a certain amount of refined grains or sugars.

This insulin response can lead to fat storage in the body, which explains some of the association between carbohydrates and weight gain [3]. However, this does not mean that carbs alone necessarily cause weight gain.

Some studies have found evidence that suggests carbohydrates do not lead to weight gain. A 2022 review examined low-carb diets and balanced-carb diets and found there was little to no difference in weight loss [4].

Another review compared low-fat, high-carbohydrate diets with high-fat, low-carb diets and examined how they each impacted weight loss and the risk of heart disease [5]. It found both diets were effective for weight control and improving heart health.

Additionally, carbohydrates do not contain more calories than the other key macros. Carbohydrates and protein both contain 4 calories per gram, while dietary fat contains 9 calories per gram [6]. However, carbohydrates (particularly, simple carbs) are typically less satiating than fats and proteins, so they may not keep you full for long, meaning you could end up overeating, which can lead to weight gain.

If you were to only eat carbohydrates, with no additional protein or healthy fat and consistently eat more than your recommended daily calories, alongside a lot of processed foods with no real nutritional content, then yes, you might gain weight. But it won't just be because you are eating carbohydrates!

Do carbs cause belly fat?

The amount of belly fat you have is impacted by several factors such as age, genetics, exercise, and diet. It is a combination of subcutaneous and visceral fat tissue, and while it is normal (and even healthy) to have some body fat in this area, having too much can be dangerous for your health [7].

Some types of food and drink, like alcohol and sugary drinks, simple sugars, refined carbohydrates and trans fats, have been associated with fat tissue and visceral fat [8].

However, it is important to remember that no one macronutrient — especially in healthy, whole food form — is responsible for an increase in body weight or fat percentage. Cutting out food groups or following low-carb diets does not necessarily flatten your stomach. Plus, even when you gain or lose weight, you cannot control which part of your body will show it.

An increase in fat around your abdomen probably means you have had an increase in body fat overall. If you are concerned about the amount of fat you have in this area, and whether you are facing health risks, you should speak to a doctor.

Can you eat carbs and still lose weight?

Despite what the weight loss industry might want you to think, you absolutely do not need to follow a low-carbohydrate diet to achieve weight loss.

At the end of the day, weight gain mostly comes down to your total calorie intake and output. If you eat fewer calories than you burn, you will lose weight. If you eat more calories than you burn, you will gain weight.

With that in mind, if you do have a weight loss goal, the best carbohydrates to eat would be those that are less processed and high in fibre — think whole grains, legumes, fruits and vegetables [9].

Complex carbohydrates are digested slowly, won't spike blood sugar, and will keep you fuller for longer with fewer calories. Whole grains and high fibre carbohydrates are also good for gut health and can lower a person's risk of developing certain conditions [10].

But carbohydrates themselves do not lead to weight gain, nor do they limit weight loss — you can maintain a healthy weight while eating carbs. In fact, as carbohydrates are a source of energy, they are important fuel for exercise, which supports weight loss and overall health.

How to incorporate carbs into a balanced diet

A healthy diet contains a balance of carbohydrates, fats, and proteins, with a bit of each in every meal and a focus on whole foods — it's unadvised to remove particular food groups from your diet (unless there is a medical reason like an allergy, etc). A healthy diet will include lots of fruit and vegetables, lean protein, whole grains, and a healthy fibre intake.

We recommend being mindful of your saturated fat intake, added sugar, highly processed foods and soft drink consumption.

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