The prevalence rates of obesity and type 2 diabetes have increased substantially in recent decades. Changes in lifestyle and diet are the first factors that need to be addressed. However, functional foods and food supplements containing fruit extracts and herbal products are also gaining increasing attention. In addition to identifying and quantitating potential bioactive compounds, it is of great importance to prove their efficacy on a cellular and molecular level. Therefore, numerous in vitro, in vivo and clinical studies have been performed and have identified bioactive compounds that modulate lipid metabolism and/or impact adipose tissue formation in a positive manner. In this review, we highlight relevant studies in the field and spotlight the applicability of alternative in vivo models, including C. elegans and Drosophila models.