Is exercise enough?
I know plenty of long distance runners that subsist on ice cream and candy bars, even well into their middle-age, and have perfect health.
Can exercise overcome poor dietary choices? If so, to what degree?
-- Corey Clark
Exercise in itself is NOT enough.
Sure, exercise can help with cardiovascular heath, respiratory health, and musculoskeletal maintenance, but you also need proper nutrition to keep all systems running properly.
Exercise does not provide Omega-3 fatty acids, fiber, monounsaturated fats, or phytonutrients.
How do you know these long-distance runners who subsist on junk are in perfect health? Have you seen their blood labs?
Just because someone is thin and has a six pack does not necessarily mean they are in perfect health. They could have high blood pressure, low bone density, and low intakes of most vitamins and minerals.