Dr Aidin Rawshani

Sugar, starch, obesity and diabetes: common misunderstandings


Sugar, starch and fast carbohydrates go hand in hand with excess weight, obesity and diabetes

For decades, Swedes have, in accordance with the recommendations of the Swedish Food Authority, been pursuing a diet that is low in fat. It has long been considered that high-fat food leads to (1) high blood lipids and therefore an increased risk of cardiovascular disease, especially heart attack and (2) weight gain, thereby at risk of developing type 2 diabetes and other complications of overweight and obesity.

Today we know that both of these assumptions have been wrong. Food rich in fat does not cause either blood fat loss or obesity. On the contrary, much speaks for the fact that fatty foods can be favorable both for blood lipids and for those who need to lose weight (read more about the PURE study). Despite this, the Swede adopted a low-fat diet and this automatically allowed more energy from carbohydrates. During the same period fast carbohydrates (sugar, starch, etc.) became more common. These carbohydrates were readily available, cheap and tasty. Today, the intake of sugar and fast carbohydrates has become unsustainable for very many. Carbohydrates pose a particular challenge for those who want to be healthy. It is a matter of choosing the right carbohydrates and limiting the quantities. In this chapter we sort out the many misunderstandings that exist about sugar and other carbohydrates.

Where are carbohydrates?

Download our compilation of how much carbohydrates are contained in different foods.

In general, it can be said that carbohydrates are found in many foods and that carbohydrates are present in many different forms. Pure sugar (powdered sugar) is a kind of carbohydrate. Potatoes contain large amounts of carbohydrates in the form of starch. Fruits also contain carbohydrates and then mainly in the form of fruit sugar (fructose). Carbohydrates are also found in lettuce and vegetables and then most often in the form of fiber, which is a special type of carbohydrates. In short, we can say that we humans can extract energy from all kinds of carbohydrates except fiber. Because we cannot break down fibers and therefore we cannot extract any energy from fibers (fibers pass through the intestine and go out via the stool). All other carbohydrates contain energy, and hence calories, for us people.

Do carbohydrates have different quality, from a health perspective?

Carbohydrates definitely have varying quality. Fast carbohydrates and refined carbohydrates can be said to be of low quality, in the sense that they do not contain much nutrition otherwise, they lead to rapid (undesirable) increases in both blood sugar and insulin, and this leads to fat formation and gaining weight. Rice and potatoes are not very much better than pure sugar. Carbohydrates that give a slow rise in blood sugar and insulin are called carbohydrates with a “low glycemic index” and that type of carbohydrates is generally better.

Are sugar and carbohydrates harmful to health?

In the food we eat today, undeniably sugar and fast carbohydrates are the most harmful ingredients, at least at the population level. Today’s food contains tremendous amounts of added sugar in various forms. A solid percentage of all the sugar and fast carbohydrates we get in us is accidental. We simply do not think that it is sugar added to the minced meat sauce, but nowadays this is nothing unusual. However, most of all sugar and fast carbohydrates are deliberately taken into account, but not everyone knows that potatoes, rice and bread are as uselessly as ordinary powdered sugar. It is difficult for many to understand this, especially since potatoes have been the foundation of Swedish home cooking for a long time.

How do I know how much carbohydrate/sugar foods contain?

Download our compilation of how much carbohydrates are contained in different foods.

Read on the nutrition declaration. It says how many grams are carbohydrates. You can count the number of grams of fiber from carbohydrates (if there is fiber in the product) and then carbohydrates that are sugar or become sugar remain in the body.

Fruit contains fruit sugar — does it mean that fruit should also be avoided?

Yes, sir. Fruit must be eaten. Fruits contain natural sugar and have several beneficial effects. The sugar contained in fruits provides a slow rise in blood sugar and a moderate release of insulin. In principle, all people can and should eat fruits, even people with diabetes.

Read more: The difference between fructose (fructose) and glucose (glucose)

Is starch something to worry about?

Starch consists of long chains of glucose. Glucose is ordinary glucose. So starch is really long chains of sugar. Potatoes, pasta and rice contain a lot of starch. Even if potatoes do not taste the same as powdered sugar, they will have the same effect in the body. From a health perspective, the difference between starch and sugar is so small that you can equate sugar and starch.

What are processed (refined) carbohydrates?

These are carbohydrates that underwent some kind of process before we eat them. As a rule, this means making the food less useful. For cereals, it can be a means to clean the germ and bran (containing useful fiber, minerals and vitamins). Examples of refined carbohydrates are: powdered sugar (white sugar), white bread, white rice, white pasta, white flour, etc. As a rule, these foods produce sharp increases in blood sugar and insulin and thus lead to weight gain (unless you limit the intake).

What carbohydrates are not processed/refined?

These products have not undergone any process until we can eat them. As a rule, they are much better options than the processed products. These include fruits, vegetables, legyms and cereals that are minimally processed. Note that potatoes and all kinds of starch are not actually processed, but despite this, it is considered normal (uselessly) sugar.

Is food with a high glycemic index (GI) harmful?

Glycemic index is a measure of how strong blood sugar rises after a meal, and hence how much insulin is released by the meal. Food with a high glycemic index provides sharp increases in blood sugar and insulin. We know today since research has been conducted on this for almost 30 years, that food with high GI is harmful. Heavy increases in blood sugar and insulin lead to ill health.

I’ve heard that fructose has low GI, but fructose is also harmful, isn’t it?

It is true that fructose has a low GI because the body cannot immediately convert fructose into glucose. Fructose used as an additive in soda (drink) and food is unhealthy, although fructose has a low GI. It also means that the concept of glycemic index (GI) does not work for all carbohydrates.

How should I think when it comes to carbohydrates?

If you find it complicated with all the terms and foods, you can try to choose the natural alternative instead. This immediately means that sugar and most fast carbohydrates must be avoided or severely limited. Always try to choose natural alternatives; these usually have low GI. Fruit sugar in whole fruits is an exception: you can and should eat fruit.

When it comes to carbohydrates, quality is important. Preferably use products of high quality, natural origin and minimize consumption of processed products. Do not be afraid to eat a lot of fat and protein, including animal fats and proteins. There is robust evidence that fat is health-promoting. Protein does not appear to harm or help our health. Read the PURE study.

Starch in rice, pasta and potatoes is to equate with ordinary sugar.

Is whole grain useful?

Whole grain can be a good option, but not necessarily. Some wholemeal products (e.g. flour) are so finely ground that the carbohydrates are released and thus give the food a rapid and sharp rise in blood sugar and insulin. Instead, you should prefer one of the following:

  • Old fashioned oats – it is not rolled, but instead cut (steel cut oats).
  • Emmerwheat (farro)
  • Whole grain and rye buckwheat equinoa
  • Whole fruits (especially non-tropical fruit)
  • Vegetables

Is low carbohydrate diet (LCHF) good for people with type 2 diabetes?

Yes, sir. There is strong scientific support for eating low carbohydrate diet (LCHF) if you have type 2 diabetes. This leads to lower blood sugar and reduced need for medicines. Read about the Science behind LCHF.

Can you eat a low-carbohydrate diet (LCHF) in the long run if you have diabetes?

Yes, it’s going well. Low-carbohydrate diet (LCHF) and a ketogenic diet (strict LCHF) also work in the long term and can have a very good effect in diabetes. In several cases, LCHF can actually lead to being “cured” of your diabetes (at least as long as you eat LCHF). This is still an area where research is underway, but more and more data suggest this.

Read our Guide to LCHF

Read our Guide to how to lose weight


Ludvig D HSPH Harvard

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Ludwig DS (2013) Examining the health effects of fructose. JAMA. 310(1):33-4.

Ludwig DS, Astrup A, Willett WC (2015) The glycemic index: Reports of its demise have been exaggerated. Obesity (Silver Spring). 23(7):1327-8.

Ludwig DS, Friedman MI. (2014) Increasing adiposity: consequence or cause of overeating? JAMA 311(21):22167-8.

Ludwig DS, Ebbeling CB. (2010) Weight-loss maintenance–mind over matter? N Engl J Med. 363(22):2159-61.

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