54. Rest and Nutrition
Deios 4:3
A person should always eat in a seated position or reclining on his left side. One should not walk around, ride, or exert himself until his food has been digested. A person who exerts himself after eating brings upon himself serious illnesses.
Deios 4:4
Day and night combine to form a twenty-four hour period. One-third of this period, which is eight hours, is enough time for sleeping. This should be towards the end of the nighttime hours so that one’s eight hours of sleep end at sunrise. One should get up before sunrise.
Editor’s note: The Rambam lived in the 12th century and his medical advice incorporates the best knowledge of his day. Consult your rabbi with any questions involving practical application of these halachos.