A study of 360,600 British adults found that high levels of exercise will not protect you from the life-shortening effects of an unhealthful diet (Brit J of Sprts Med, July 12, 2022). People who ate an unhealthful diet and exercised vigorously every day still were at increased risk for dying from heart disease, cancer, or any cause.

As you would expect, those who had the highest levels of physical activity and highest intake of a quality diet had reduced risks of death, compared to those who were inactive and ate the worst diet:
• 19 percent reduced risk of death from heart disease
• 27 percent reduced risk of death from certain cancers
• 17 percent reduced risk of death from all causes
The definition of a high-quality diet for this study was one that had at least five portions of fruit and vegetables every day, two servings of fish per week, and a low intake of red meats and processed meats — a diet that is high in anti-inflammatory foods and low in pro-inflammatory foods.

Exercise helps to prevent heart attacks, but exercise does not prevent plaques from forming in arteries. What you eat is far more important in determining how much plaque you have in your arteries, so even competitive master athletes should follow a heart-healthy diet. See my report on Exercisers Should Follow a Heart-Healthy Diet