Fact Check - The sense and nonsense of low-carb diets

In recent years, the low-carb trend has firmly made its way into the rhetoric surrounding "healthy" eating. Low-carb options on menus, advertisements for fitness and diet foods and popular diet gurus reinforce the idea that carbohydrates are best given a limited place in our diet. The low-carb trend manifests itself in various forms.

(Those who would like to get some more information about carbohydrates first - What are they? What are the different types? And what is their function? - can do so here).

In a low-carb diet, the intake of carbohydrates is greatly reduced.

The diet is recommended by some doctors for patients with Type 2 Diabetes. There are studies that show that, in some cases, it contributes to a positive effect on blood sugar, blood pressure and cholesterol. The important note to add here is that these recommendations always look at the quality of the carbohydrate sources, and mainly limit the simple carbohydrates. Thus, it is never about limiting carbohydrates in general. Moreover, this is always done under the strict supervision of a physician/dietician.

A second reason why people sometimes choose a low-carb diet is to lose weight. Its effect as a slimming diet is -as with all diets- based on a reduced calorie intake. So it will only work if you consume fewer calories in total than with your previous diet. The feeling of hunger is thought to be suppressed in three ways: (1) the higher proportion of protein provides a longer feeling of satiety (2) your body goes into 'ketosis' (it switches to burning fat), which is accompanied by an increase in the satiety hormones and (3) simple sugars promote the feeling of hunger, so by cutting these out the appetite is also reduced.

Many people start such a diet without professional supervision, making it difficult to maintain and causing you to quickly regain the pounds lost as soon as you switch back to your old eating pattern. Moreover -if you are not careful- it can lead to muscle breakdown, since carbohydrates are responsible for the hormones that stimulate muscle growth. So it is wrong to simply assume that an increased protein intake will prevent muscle breakdown. Furthermore, there may occur a shortage of a number of vitamins and minerals which are mainly found in carbohydrate-rich foods, such as folic acid, vitamin C, iron and magnesium. Due to the higher fat and protein intake, it can also have a negative impact on your kidneys and cardiovascular system.

A combination diet is based on the assumption that the different enzymes you need to digest carbohydrates, fats and proteins work against each other. Therefore, you need to keep certain food groups such as carbohydrates and proteins separate. This is based on very poor scientific research, since the different food groups are digested separately in your body, each using its own enzymes. It also claims that fruit after your meal causes fermentation and even putrefaction in your stomach. Fermentation is perfectly normal, however, and only if your intestinal flora is disturbed (by illness, stress or a one-sided diet) could this cause digestive problems. Apart from the fact that the diet is based on a misinterpretation of digestive physiology, it is also very impractical: foods often contain a combination of proteins, fats and carbohydrates, which severely limits the list of what you can eat. Therefore, it is very challenging to eat a versatile and varied diet, which can lead to significant nutritional deficiencies.

The paleo diet assumes that we should all eat like our ancestors, the primordial humans, did. It focuses on pure and unprocessed food -so far, so good-, but in a very rigid way: only meat, fish, eggs, vegetables, fruits, natural oils, nuts and seeds are allowed. The theoretical recommendations amount to 18 En% protein, 59 En% fat and only 20 En% carbohydrates. Just to recap, the general WHO guidelines are 15 En% protein, 30 En% fats and 55 En% carbohydrates. No distinction is made between saturated and unsaturated fats and meat consump