An excerpt from Tales from the Trenches: A life in Primary Care.

For nearly four decades in medical practice, I’ve been asked countless times about the best supplements or vitamins for improving health. Despite widespread hopes that pills can unlock vitality and longevity, the truth is less glamorous and far more powerful: The single best prescription for health is regular physical activity. Exercise, not supplements or medications, is the most proven, accessible, and effective intervention for preventing disease, enhancing mental and physical well-being, and extending life.

Research on the health benefits of movement is extensive and irrefutable. More than 100,000 scientific articles support the profound effects of regular exercise. Conversely, physical inactivity is linked to over 40 medical conditions, including heart disease, type 2 diabetes, certain cancers, obesity, cognitive decline, anxiety, and depression. These are not minor concerns—they are the leading causes of death and diminished quality of life. The good news is that exercise significantly reduces the risk or severity of nearly all of them.

Exercise works because our bodies evolved to move. Skeletal muscles make up around 40 percent of body weight, and their function is tied to nearly every system in the body. When muscles are engaged regularly, they trigger a cascade of beneficial physiological changes. Even small increases in movement can yield large health benefits, especially for sedentary individuals.

Understanding what qualifies as exercise is important. Sedentary activity includes sitting or lying down for extended periods. Light activity includes slow walking and minimal-effort chores. Moderate activity encompasses brisk walking, casual cycling, housework, yard work, and dancing. Vigorous activity includes running, heavy lifting, sports, and anything that increases heart and respiratory rates. Medical guidelines recommend at least 150 minutes of moderate activity per week, which can be broken down into short, manageable sessions—such as three brisk walks a day.

The benefits of exercise extend across virtually every major body system:

• Cardiovascular system: Exercise strengthens the heart muscle, lowers blood pressure, improves blood lipid profiles, and stimulates the growth of new blood vessels. It also protects the arteries from blockages and reduces inflammation. People who exercise regularly can reduce their risk of death from cardiovascular disease by up to 30 percent.
• Metabolic health and diabetes: In type 2 diabetes (T2DM), the body becomes resistant to insulin, leading to high blood sugar. Exercise combats this by increasing glucose uptake in muscles and improving insulin sensitivity. Studies have shown that exercise alone can reduce the risk of developing diabetes by nearly 50 percent, and when combined with diet, the reduction is even greater.
• Immune system: Exercise boosts immune function by mobilizing white blood cells and improving their efficiency. It also reduces chronic inflammation, a root cause of many diseases. Fit individuals have stronger immune responses and even show better vaccine efficacy.
• Hormonal and endocrine system: Physical activity influences hormone levels beneficially. It reduces stress hormones like cortisol and boosts growth hormone and testosterone, aiding in recovery, muscle growth, and energy balance. It also improves how the body uses insulin.
• Nervous system and mental health: Exercise improves brain function, enhances neuroplasticity, and helps prevent or slow neurodegenerative diseases like Alzheimer’s and Parkinson’s. It also elevates mood by adjusting brain chemicals linked to depression and anxiety. Notably, exercise has often been shown to be more effective than medication in treating these mental health conditions.
• Musculoskeletal system: Regular physical activity strengthens muscles and bones, increases endurance, and prevents sarcopenia (age-related muscle loss). Muscles even secrete myokines, hormone-like substances that regulate inflammation and promote healing throughout the body.

Given these immense benefits, it is clear that movement should be a core part of medical treatment—not just an afterthought. In fact, the American College of Sports Medicine launched a campaign called Exercise is Medicine to emphasize this very point.

For those new to exercise, the key is to start small and be consistent. A five-minute walk, taken multiple times per day, can be transformative. Finding activities you enjoy—such as dancing, gardening, or hiking—makes it easier to maintain the habit. Scheduling exercise like any other priority (e.g., brushing your teeth) helps create long-term consistency. Tools like the 7-minute workout or light dumbbell routines at home offer accessible ways to build strength and stamina without major time investment.

Ultimately, the message is simple but profound: Exercise is the best prescription for better health. It requires no prescription pad, costs nothing, and has no harmful side effects—only life-enhancing ones.

George F. Smith is an internal medicine physician and author of Tales from the Trenches: A life in Primary Care.