Constraining Newtonian stellar configurations in f(R) theories of gravity

We consider general metric f(R) theories of gravity by solving the field equations in the presence of a spherical static mass distribution by analytical perturbative means. Expanding the field equations systematically in O(G), we solve the resulting set of equations and show that f(R) theories which attempt to solve the dark energy problem very generally lead to γPPN=1/2 in the solar system. This excludes a large class of theories as possible explanations of dark energy. We also present the first order correction to γPPN and show that it cannot have a significant effect.