The growth phase plane is a geometrical construction which integrates the dynamics of starvation and growth under ad libitum and controlled feeding. The ordinate and abscissa of the plane are weight and food intake respectively; time is implicit. All the possible weight and intake data for an animal lie in the rectangle of dimensions mature weight (ordinate) versus mature food intake (abscissa). Some experiments by Taylor, feeding cattle at constant intakes, showed the diagonal to be a collection of equilibrium points where growth rates are zero. Some experiments on complete and partial inanition analysed by Parks, showed the weights falling towards the diagonal as points of equilibrium. Thus the Taylor diagonal divides the growth phase plane into two regions namely the partial starvation region above the diagonal where energy intake is less than required for maintenance of weight, and the controlled growth region below the diagonal where energy intake is greater than required for maintenance. The ad libitum growth phase curve is the lower limit of the controlled growth region. A linear first-order inhomogeneous differential equation with food intake as the driving function is proposed to describe the dynamics of starvation and controlled growth. The implications of the equation and the phase plane are discussed.