Introduction and objective:
Among the unconventional diets, the ketogenic diet (KD) is currently gaining popularity. The aim of the study was to determine the motivation of active and physically fit women to apply KD, to examine whether the results of KD met the expectations and to assess their diet and nutritional status.

Material and methods:
The study covered 500 women aged 40.5 ± 12.2 years, including: 250 – in the course of KD lasting one and a half month, on average (Group 1), and 250 – who had already completed KD lasting for 3 months, on average (Group 2). The frequency of consumption of products that are a source of fats, proteins and carbohydrates was evaluated in 2 categories: often (several times a week to several times a day) and rarely (once a week – never). Nutritional status was assessed in particular BMI ranges.

Results:
As many as 75% of women from both groups used KD to lose weight and most of them declared that they had achieved the intended goal. Products allowed and recommended in KD were consumed frequently by the majority of women, but nutrition mistakes were also made; 62% of women used dietary supplements. As a result of KD, the percentage of women with excess body weight (obesity and overweight) decreased in Group 1 from 87% – 54%, and in Group 2 – from 87% – 37%. The number of overweight women decreased statistically significantly. The vast majority of women undertook KD without consulting a doctor or a dietician. In Group 2, malaise was a frequent cause of discontinuation of the diet.

Conclusions:
It is necessary to involve physicians and nutritionists more in promoting knowledge about contraindications and possible negative consequences of introducing the body into a state of nutritional ketosis, and the need to check the general health condition before implementation and during the use of KD.