Energy balance (intake and expenditure) is under the control of complex and redundant neural pathways that regulate feeding behavior and energy metabolism in response to availability of nutrients in the circulation or in fat stores. A number of hormones are secreted from peripheral organs and act in the hypothalamus to influence appetite and energy expenditure. This review will summarize recent progress in the identification of the neural pathways that respond to peripheral signals of energy availability such as leptin and macronutrients. Although the impact of environmental factors on obesity is underscored by the modern obesity epidemic, new insights into the pathophysiology of weight control provide new targets for therapeutic intervention for obesity.