Today, there are many different types of diets, and the ketogenic diet is one of them. It relies on a minimal intake of carbohydrates, an individually adjusted protein intake, and a high proportion of fats. The principle behind this is that the body has to use an alternative source of energy due to the lack of carbohydrates. These are what are known as ketone bodies, which can be produced from fats. The metabolic state that sets in is called ketosis and can help with the loss of adipose tissue. Since ketone bodies are excreted in the urine, their detection in the urine can serve as a dietary control.
Types of Ketone Bodies
During ketosis, the body forms three different ketone bodies: acetoacetate, beta-hydroxybutyrate, and acetone. Beta-hydroxybutyrate is quantitatively the most important and accounts for the largest proportion in established ketosis. Acetone is primarily exhaled through the breath and is responsible for the typical, slightly fruity breath in ketosis. Acetoacetate and acetone can be reliably detected in urine – beta-hydroxybutyrate, however, cannot.
How Urine Test Strips Work – and Their Limitations
Commercially available urine test strips, often known as Ketostix, are based on a chemical reaction with sodium nitroprusside. This reaction only responds to acetoacetate and, to a lesser extent, to acetone. The color scale typically ranges from light yellow-brown to pink and then to a strong violet, depending on the concentration. The darker the discoloration, the more ketone bodies are excreted.
What many do not know: In the first few weeks of a ketogenic diet, the urine test works well and provides a reliable signal. After about four to eight weeks, however, the body adapts to the new metabolic state, utilizes ketone bodies more efficiently, and primarily excretes beta-hydroxybutyrate – which urine test strips do not detect at all. The result: The test may become negative again or only weakly positive, even though the body is demonstrably in ketosis. High fluid intake or the timing of the measurement can also falsify the result, as highly diluted urine shows correspondingly low ketone concentrations.
Alternatives to Urine Measurement
Those who wish to accurately monitor ketosis over a longer period usually resort to measuring beta-hydroxybutyrate in the blood. This is considered the gold standard because it directly detects the most important ketone body and remains reliable even after weeks of adaptation. Devices for this function similarly to blood glucose meters and are now readily available. In addition, there are breath analyzers that detect exhaled acetone – these are non-invasive and reusable, but they only provide a limited correlation with blood values and are not suitable for people with diabetes.
Ketosis as a Form of Nutrition – with a Healthy Perspective
The ketogenic diet can temporarily help reduce fat tissue and has evidence-based therapeutic applications in certain medical areas, such as drug-resistant epilepsy in childhood or GLUT1 deficiency syndrome. However, the German Nutrition Society (DGE) critically evaluates it as a long-term dietary form for healthy individuals and points out possible risks such as nutrient deficiencies, altered blood lipid levels, and increased kidney strain. It is not recommended for certain pre-existing conditions – particularly type 1 diabetes, pregnancy, or advanced kidney diseases. Therefore, anyone wishing to implement a ketogenic diet over a longer period should ideally plan and monitor it together with a physician or a qualified nutrition professional.
Sources
AWMF – S1 Guideline “Ketogenic Diets” (022-021, as of 2022): register.awmf.org
German Nutrition Society (DGE): dge.de
German Diabetes Society (DDG) – Practical Recommendations for Nutritional Therapy: ddg.info
DocCheck Flexikon – Ketone Bodies: flexikon.doccheck.com
Stiftung Gesundheitswissen – Ketogenic Diet: stiftung-gesundheitswissen.de
The content of this article is for general information purposes only and has been prepared with the utmost care based on recognized medical sources. It does not constitute a healing statement
