A combination of Eurycoma longifolia and citrus peel extract are provided in a supplement to promote weight loss and help dieters maintain high energy levels by reducing the body's normal shift to a catabolic state during weight loss. The Eurycoma longifolia root extract preferably includes eurypeptides and the citrus peel extract preferably includes tangeretin, nobiletin, and sinensetin. The supplement can be in any suitable form and is preferably administered in conjunction with a weight loss regime that includes a caloric deficiency diet and an exercise program.