Overweight and obesity are the plague of the 21st century, spreading wider and wider. According to research conducted in Poland in 2014, they have already been diagnosed in 62% of adult men and 46% of women. Excessive body weight is a result of inadequate energy intake compared to insufficient energy expenditure. Unfortunately, easy access to highly processed food with high sugar content, coupled with low fiber intake and very low physical activity, paves the way to obesity and, consequently, to metabolic diseases such as insulin resistance, diabetes, coronary heart disease, and hypertension. How can we protect ourselves from overweight? It turns out that taking care of the composition of gut microbiota is an effective way.