For many chronic conditions, rest has long been the standard of care, but we are now witnessing a true paradigm shift: scientific studies show that physical activity (PA) has undeniable benefits for people with chronic diseases. These benefits are all the more significant when PA is introduced early after diagnosis. Consequently, physical activity—even for patients in advanced stages of their diseases—must be an integral part of the treatment of chronic diseases. It should be systematically prescribed as early as possible in the care pathway for each of the conditions studied. Even more impressive, the scientific literature now demonstrates with certainty that certain conditions can be cured by physical activity alone, provided that the patient commits to it long-term. The expert panel of the French National Institute of Health and Medical Research (Inserm) recommends that physical activity be prescribed before any drug treatment, that is, as a first-line treatment for mild to moderate depression, type 2 diabetes, obesity, and peripheral arterial disease.