Background: High percentage of the Polish suffer from overweight and obesity. According to previous report prepared for the government, the percentage of overweight and obese people in Poland was 36.6% and 16.7% respectively, which constitutes 53.3% of the adult population in Poland. This state that body mass of a statistical -adult inhabitant of Poland is over the average one, calculated for 28 countries of the European Union. It was assumed that 25% of individuals aged ≥15 years in 2015 experienced NAFLD in France, Germany, Spain and the UK.

Obesity results from unhealthy lifestyle - too high calorie intake, too little physical activity and low fiber content in the diet. The most common clinical complication of overweight and obesity is non-alcoholic fatty liver disease (NAFLD). In the United States, 20-30% of adults suffer from NAFLD, while in the European adult population the percentage varies 14-21%. In addition, 30-50% of diabetics and 93% of people with hyperlipidemia suffer from NAFLD. The incidence of NAFLD increases with age (the disease is diagnosed between 40-65 years of age predominantly), and is sex-dependent - males suffer from this disease most often compared to women. NAFLD incidence within obese patients (BMI≥30) was found to be equal to 78%. The NAFLD risk factors include: obesity, environmental factors (low physical activity, fructose in the diet) changes in the intestinal microbiome (induced by eg. too low fiber supply) epigenetic factors, insulin resistance and genetic factors So far, there is no effective drug that can be effective in NAFLD therapy. Current treatments include changes in eating habits (proper composition of meals) leading to weight loss and thus remodeling the gut microbiome, as well as adequate physical activity. One of ingredients with beneficial effects for liver structure and function (liver cells - hepatocytes) is fiber. Plant fiber is a key component of the diet, preferably regulating metabolic processes and maintaining a healthy body. This is because the plant fiber acts as a nutrient for the intestinal flora (microbiota) and it "travels" through the intestine, ensuring its good peristalsis and proper stool formation. Undigested plant fiber including xylan polysaccharides, pectin, arabinose-containing carbohydrates as vegetable pectins, cellulose, hemicellulose, resistant starch reach unchanged into the colon, where they are metabolized by intestinal microorganisms. The fiber serves as substrate for the synthesis of short-chain fatty acids (SCFAs): propionate, acetate and butyrate. Especially the latter one - butyric acid (butyrate) is considered as a potential therapeutic agent in NAFLD. Butyrate can be treated exceptionally because of its high biological activity, which includes modulations of epigenetic functions (butyrate is a histone deacetylase (HDAC) inhibitor), energy functions (70% ATP synthesis takes place in colonocytes) and functions as a G protein-coupled receptor activator (GPCR). Consequently, the content of prebiotic vegetable fiber in the diet controls the productions of butyrate. It was shown that already after 24 hours since higher fiber supply (\> 30g per day), the diversity of the microbiota was higher and the SCFAs synthesis increased. Meanwhile, the amount of fiber consumed in industrialized countries is very low. It was estimated that adults in the US provide an average of 12-18 grams of dietary fiber per day. In Europe the fiber intake varies between 16-29 g/day. At the same time in African communities (Burkina Faso, Tanzania) dietary fiber intake is high providing balance within microbial milieu within the gut, thus greater SCFA synthesis and lower titre of inflammatory factors. In comparison, in Poland the average consumption of fiber in adults is 19 - 34 g / day for men and 19 - 20 g / day for women. On the other hand most of the Nutritional Societies in the world recommend fiber intake not less than 25 g / day for women and 38 g / day for men.

As a result of inappropriate diet incl. low fiber intake obese patients show disturbances in the microbiota composition and metabolism, what results in dysfunction of intestinal barrier and increases the influx of proinflammatory substances to the liver. In this way gut dysbiosis may trigger and aggravate the liver injury in NAFLD.

Aims: The project aims to create low-calorie bars / snacks with an increased fiber content (12 g / bar), which would be a convenient and easy-to-eat snack replacing the second breakfast and/or afternoon tea. The main scientific aim is to examine whether a simple correction of the diet consisting of the extra supply of fiber in NAFLD patients will improve the microbiome composition and metabolism (inc. fermentation and production of SCFA), will support the intestinal barrier and eventually improve liver function.