The context: "This" refers back to the previous verses, trusting the Lord, not being wise in your own eyes, and turning away from evil.
This verse anticipates what modern medicine calls psychosomatics: the direct link between our spiritual/emotional health and our physical health.
"Health to your body"
When we trust God and turn away from evil, we lower our cortisol levels (the stress hormone). Anxiety, fear, and guilt are toxic to the body; trust and peace are medicinal.
"Nourishment to your bones"
Dry bones in the Bible represent a lack of life, deep depression. The "nourishment" here is the moisture, the vitality that comes from the inside out.
Solomon is saying: a clean conscience and a heart resting in God are the best preventive medicine there is. The stress of trying to control everything alone (being wise in your own eyes) makes us sick.
"The Root of Rejection" — Joyce Meyer
Joyce talks extensively about how rejection and bitterness cause physical illness. The emotional stress of trying to be accepted, or grudges held onto, "dry out the bones." Healing from rejection (finding acceptance in God) literally brings physical health.
"The Knight in Rusty Armor" — Robert Fisher
The Knight's armor left him stiff, sore, and unable to feel. It was the physical manifestation of his emotional block. When he learned to trust and to cry (releasing control), the armor fell away and his body found "nourishment" again.
"O Poder da Autorresponsabilidade" — Paulo Vieira
People who complain, blame, and criticize (victims) live in a state of tension and negativity, which breeds illness. The person who takes ownership, focusing on solutions and gratitude, generates a body chemistry of health and energy.
Jesus presented Himself not only as Savior of the soul, but as the Doctor of doctors. In His ministry, He healed bodies to demonstrate He had authority to forgive sins (Mark 2). He said: "Peace I leave with you; my peace I give you" (John 14:27). That Peace (Shalom) isn't just the absence of war, it's the fullness of well-being, physical and emotional wholeness.
Being in Christ means having access to the "Living Water" that hydrates the soul and keeps our "bones" from drying out. Communion with Him is health for the body.