 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. 