Obesity is not merely a cosmetic problem, but also represents an unhealthy state, currently accepted as an illness. It is defined as an abnormal increase in body fat (though not necessarily in body weight). In adult men with an average weight, the percentage of body fat is in the order of 15-20%. The prevalence of obesity has been increasing world wide during the past few years, and it is reaching epidemic proportions in the industrialized countries (WHO, 1998). This problem represents an enormous burden on health care system and, most importantly, the quality of life of the affected individuals is substantially lowered. Although, extensive research and public awareness have been made over the previous decades, the proportion of people affected is still rising. Medicinal plants, plants used for eating purposes, and other natural products, are mainly complex products having several components with different chemical and pharmacological characteristics. Several medicinal plants have shown promising results to control obesity. In this book the use of Foeniculum vulgare in the management of obesity is discussed.