Do carbohydrates make you gain weight? Myths and facts about carbohydrates in the diet

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There are many myths about carbohydrates circulating on the Internet. One of them says that fruit should not be eaten in the evening. According to this myth, fruit can only be eaten in the morning because if eaten in the evening, it promotes weight gain. This is not true. Only a positive energy balance, commonly referred to as excess calories, causes weight gain, not specific products. Fruit does not change its calorific value during the day. Nothing bad will happen if we eat the fruit after 6 pm, referring to the common opinion that after this hour you should not eat anything. It’s important to watch your body. Fruit can be eaten regardless of the time of day if well tolerated.

However, the time of fruit consumption is critical for diabetics because fruits are a source of simple sugars. [6] Diabetics should refrain from eating fruit before bedtime. This is because some fruits have a high glycemic index. These are, for example: ripe bananas or grapes. Consuming them in the evening causes a sharp increase in blood glucose levels and a worse mood the next day. Long-term high blood glucose levels can lead to serious health consequences. Untreated diabetes can lead to vision damage and even loss, and to the development of kidney failure.

Do carbohydrates make you gain weight?

Carbohydrates by themselves are not fattening. Gaining weight causes only a positive energy balance in the diet. We should not exclude carbohydrates from the diet. Their proper supply is important for the proper course of metabolic processes. Carbohydrates provide energy in the form of glucose, which is essential for the work of the brain, muscles, and nerves. In addition, complex carbohydrates are a source of dietary fiber. It improves bowel function and reduces cholesterol absorption, preventing atherosclerosis. A well-balanced diet provides proteins, fats and carbohydrates, according to individual needs. [1]

What are carbohydrates, and what is their role?

Carbohydrates are also called sugars. They are divided into simple and complex carbohydrates. They perform many functions in the human body, the most significant of which is providing energy. 1 gram of carbohydrates provides 4 kcal. Glucose supplied from food is the only source of energy for the brain and red blood cells. The use of glucose by the cells is related to the maintenance of a relatively constant concentration of glucose in the blood. Adequate blood glucose levels are related to the metabolism of fats and proteins. Glucose is not only a source of energy, but also serves to synthesize cell structures during growth. Complex (non-digestible) carbohydrates, which form dietary fiber, are also responsible for blood glucose levels. Products that are a source of complex carbohydrates have a lower glycemic index than products rich in simple sugars (sweets, fast food). Thanks to the lower glycemic index, there is a gradual secretion of glucose from the liver into the blood. The level of glucose in the blood is stabilized, and its secretion is even. Thanks to this effect, products rich in complex carbohydrates (e.g., wholegrain bread, groats) provide a longer feeling of satiety.

Carbohydrates play an important role in fat metabolism. Too little glucose intake results in incomplete conversion of fats. In this situation, ketone bodies accumulate in the body. Their excess leads to ketoacidosis. Increasing the acidity of the blood is not good for the body. It can lead to general weakness, fatigue, headaches, and muscle pain. [2]

The beneficial effect of dietary fiber should also be mentioned. It is necessary for the proper functioning of the intestines. Fiber stimulates the digestive system to work, thanks to which it shortens the intestinal transit time. It also has a positive effect on lipid parameters. It lowers the concentration of total cholesterol in the blood and LDL cholesterol. This is because it reduces the absorption of dietary cholesterol in the small intestine. In addition, fiber forms insoluble complexes with cholesterol in the large intestine and helps to remove them from the body. Sources of fiber include whole grains, legumes, and vegetables. [1], [2]

Sources of carbohydrates

Good sources of carbohydrates are cereal products, vegetables, legumes, and fruits. These products provide complex carbohydrates, which are critical in maintaining a stable blood glucose level. Wholegrain products (bread, pasta) and vegetables are a source of valuable carbohydrates. Complex carbohydrates give the feeling of satiety faster than simple carbohydrates, and the dietary fiber contained in wholegrain products improves the functioning of the digestive system. It has a positive effect on the removal of undigested residues and harmful substances. [2]

Products rich in simple carbohydrates in excess negatively affect the body. These are, for example, sweets, fast food and sweetened drinks. These products contain large amounts of simple sugars, mainly glucose and fructose. Consumed in excessive amounts, they can contribute to weight gain and the development of diabetes. Foods that provide only simple sugars and are eaten in excessive amounts can make it difficult to lose weight. Highly processed food provides mostly “empty calories”. Candies and bars have a high glycemic index, so they do not provide satiety for a long time. Their consumption causes a sharp increase in blood glucose levels, and then a sharp decrease. As a result, fast food and sweets do not satisfy the feeling of hunger for long. Eaten in excess can lead to the development of diabetes and atherosclerosis. [4]

Carbohydrate content in selected products

ProductCarbohydrates in 100 gFiber in 100 g
Oat flakes69,3 g6,9 g
White rice78,9 g2,4 g
Banana23,5 g1,7 g
Raisins71,2 g6,5 g
Carrot8,7 g3,6 g
Potatoes18,3 g1,5 g
Wheat bread54,3 g2,7 g
Wholemeal rye bread51,2 g8,4 g

Source: Wartość odżywcza wybranych produktów spożywczych i typowych potraw., PZWL, Warszawa 2020

Carbohydrates and slimming diet

Many myths related to carbohydrates say that during weight loss they should be limited. There is a grain of truth in this. When losing weight, we should focus on complex carbohydrates. However, it would be good to limit the consumption of simple carbohydrates. On a slimming diet, it is important that meals ensure satiety for a longer time. Unfortunately, products that are mainly a source of simple sugars have a high glycemic index. After eating them, we only feel full for a short time. This contributes to snacking between meals. If we want a meal to be filling, we should add complex carbohydrates to it. They provide dietary fiber and thus reduce the glycemic index of the dish. [3] Thanks to this, we will avoid snacking and “unnecessary” calories. For example, instead of just eating a banana, add it to yogurt along with oatmeal and nuts. Such a meal will provide us with all the necessary nutrients, and we will feel full for a long time.

Dietary fiber plays a significant role in the weight loss process. It not only improves bowel function, but also regulates the processes of glucose release into the blood. Fiber-rich foods include: legumes, raw vegetables and nuts. Adding these products to meals will make our diet more filling and stabilize blood glucose levels. Snacking may also disappear because we will not feel hunger and a sudden drop in energy so quickly. This will have a very positive effect on your health and well-being. Fiber will help with constipation and improve the condition of the intestinal microflora. It can even slightly speed up weight loss by reducing snacking and feeling full longer. [5]

When are carbohydrates causing weight gain?

Carbohydrates can make you gain weight if you consume too much of them. It is easy to overdo it with products that are a source of simple sugars. Since they do not give a feeling of satiety for a long time, after eating them we get hungry quickly. This can happen when eating fast food or sweets. After eating them, there are large fluctuations in blood glucose levels because they provide large amounts of simple carbohydrates. As a result, you feel hungry quickly after a meal. Energy levels are also suddenly lowered by fluctuations in glucose levels. This lowers our mood and increases the tendency to snack. On a reducing diet, it is best to limit the consumption of excessive amounts of simple sugars. However, it should be remembered that we do not get fat from specific products, but from the excess of calories consumed.

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Carbohydrates vs. Fats – Which is More Fat?

According to the theory, fats are more caloric. 1 gram of fat provides 9 kcal and 1 gram of carbohydrate provides 4 kcal. [2] However, it all depends on how much of the product we consume. It is easy to overdo it with both fats and simple carbohydrates. Fats and simple sugars have their hidden sources. Fast food, bars, and candies contain large amounts of both simple sugars and saturated fats. Because these products do not provide satiety for a long time, we start to feel hungry faster. And this causes us to eat them in larger quantities to satisfy our hunger. Thus, we provide fats and simple sugars in uncontrolled amounts. In addition, fats and carbohydrates are involved in creating the taste of food. [2] Fats enhance the perception of taste. Due to the increased palatability of high-fat products, their increased consumption may occur. And thus to an unknowingly significant increase in the caloric content of the diet. [7]

Bad vs. Good Carbs – Is There a Difference?

Simple and complex carbohydrates are essential in the diet. They are responsible for the proper functioning of the brain, nerves, and muscles. Additionally, dietary fiber is necessary for our intestines to function properly. However, eating too many simple carbohydrates is not good for your health. Simple sugars include mainly glucose, fructose, and galactose. Products rich in simple sugars maintain long-term increased blood glucose levels. This condition can lead to the development of diabetes and other dangerous health consequences. Too much simple carbohydrates provide sweets, so they should be limited. Fruit is a much better source of simple sugars. In addition to simple sugars, fruits also contain fiber, vitamins, and minerals that are essential for humans. [2]

However, a more favorable choice will be products rich in complex carbohydrates. Especially for people who want to reduce body weight. Whole-grain pasta, groats and raw vegetables will ensure a longer feeling of satiety and provide the necessary vitamins and microelements. [7]

List of the best carbohydrates source
ProductCarbohydrates in 100 g
Brown rice76,8 g
Walnuts14 g
Parsley root10,5 g
Potatoes18,3 g
Cooked lentils57,5 g
Banana23,5 g

Source: Wartość odżywcza wybranych produktów spożywczych i typowych potraw, PZWL, Warszawa 2020


Do not eliminate carbohydrates from your diet. You have to remember that they are necessary for the proper functioning of the body. They are the main source of energy and have a positive effect on our health. Both simple and complex carbohydrates should be included in our diet. Carbohydrates by themselves are not fattening. Weight gain only causes excess energy, not specific products. What’s more, carbohydrates can even promote weight loss. Therefore, the more complex carbohydrates should be included in our diet. You should consciously compose meals so that they provide us with all the necessary ingredients. This will keep us full for a long time and reduce snacking between meals. Thus, we will not eat “unnecessary” calories, and we will have more energy during the day.


  1. Jarosz M., Sajór I., Gugała-Mirosz S., Nagel P., Czy wiesz, ile potrzebujesz węglowodanów? Instytut Żywienia i Żywności 2019
  2. Cichon R., Wądołowska L., Węglowodany., red. Gawęcki J., Żywienie człowieka. Podstawy nauki o żywieniu. Tom I. Wydawnictwo Naukowe PWN. Warszawa 2010, 155-179 
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  6. Zalecenia kliniczne dotyczące postępowania u chorych z cukrzycą 2021 Stanowisko Polskiego Towarzystwa Diabetologicznego 
  7. Skotnicka M., Duraj N., Rola składników odżywczych w regulacji sytości organizmu., Ann. Acad. Med. Gedan. 2015, 45, 79-87