Beloved, I wish above all things that thou mayest prosper and be in health, even as thy soul prospereth. 3 John 2.
What is it you usually think of when you think of health? Many think of Seventh-day Adventists as the people who don't eat meat. But diet is not the major issue in health. Jesus promised His followers that He and His Father would come and dwell with them. He said that He would manifest Himself to us. How does He do this? Well, we could say, By the things of nature; but He does that for everybody, including the skeptic and infidel and agnostic. People who curse God have much of the natural manifestations of God. So His manifestation must be by means of a more direct communication.
"The brain nerves that connect with the whole system are the medium through which heaven communicates with man and affects the inmost life. Whatever hinders the circulation of the electric current in the nervous system, thus weakening the vital powers and lessening mental susceptibility, makes it more difficult to arouse the moral nature."--Education, p. 209. There are three parts of the brain--and the first that is affected by stimulants is the higher centers, where spiritual communication takes place.
The body and mind are closely related. "The body is the only medium through which the mind and soul are developed for the upbuilding of character."--The Ministry of Healing, p. 130. So the mind is the only medium of communication with God. And the body is that through which the mind and soul are developed. Whatever affects the body affects the mind. It is through the mind that God manifests Himself to us, so when the body and mind are affected, our communion with Him is affected.
So what does insufficient sleep do in terms of affecting communion with God? What does lack of exercise do to our communion with God? What does overeating do in terms of communion with God? What do drugs and alcohol and other harmful substances do in terms of communion with God? Are these fair questions? Satan is able to come in and control us when he manages to control our minds. But the clearer our minds become, and the more healthy our bodies, the easier it is for us to let God control us according to His will.