Magnetic resonance of the body offers different techniques for mapping fat deposits (MR Imaging) and analysis of organs with small amounts of lipids (MR Spectroscopy). Possible approaches for whole-body assessment of adipose tissue are presented and discussed and spectroscopic examinations in different organs are depicted. With magnetic resonance imaging (MRI) it has been shown that obesity per se is not a marker for metabolic failure, but depends on regional variations of body composition and ectopic lipid accumulation. In addition MRI of the brain is a powerful research tool to understand the brain's role in the development and maintenance of obesity and the overconsumption of foods in obese individuals. Sonography has a low accuracy in estimating hepatic steatosis until now. New sonographic methods have been evaluated to detect hepatic steatosis by physical properties of fatty tissue as tissue stiffness, sound absorption or sound speed. Nuclear medicine and in particular Positron Emission Tomography (PET) methods are used to explore central pathophysiology, brown adipose tissue activity and alterations in homeostatic feedback and gut-brain communication.