The Nekhoroshev theorem describes the exponential stability of motion in perturbed Hamiltonian systems. Its spectral formulation is used to assess the stability of motion in dynamically diverse regions of the asteroid Main Belt. The obtained spectra exhibit a clear distinction between line, continuous and irregular structure, thus indicating regular vs. chaotic motion. We briefly describe the theorem and its spectral formulation, and show different dynamics revealed. The procedure of checking the fulfillment of conditions of convexity, quasi-convexity or 3-jet non-degeneracy for application of the theorem is also described, as well as an example of its use in combination with the spectral formulation of the theorem given.