<qa>  What is the relationship between metabolic state and anxiety?To better understand the relationship between metabolic state and anxiety, we will examine whether changes in metabolic state influence anxiety in human subjects. We will use whole-brain functional magnetic resonance imaging fMRI to identify the neural mechanisms that underlie metabolic state-dependent changes in the response to anxiety-inducing stress. In a randomized crossover design, participants will be tested in a well-established behavioral task that elicits anticipatory anxiety in two separate sessions that differ with respect to their metabolic states. We aim to perform a fine-grain analysis of changes in neural and physiological responses to this anxiety-inducing task as a function of metabolic state. Using fMRI as well as non-invasive psychophysiological measures, we will characterize whether there are systematic differences in the neural and psychophysiological experience of anxiety across different metabolic states in obese as compared to lean individuals. 