The most likely cause of fatigue from exercise is dehydration, so drink a glass of water 20 minutes before exercise and after exercise. Nutrition Eliminate alcohol, excess coffee, cigarettes, sugar. Don't eat junk food. Increase your intake of fruits, vegetables, salads. Minimize your intake of fats and fried foods.
Some people have dairy sensitivities.
If that is the case, eliminate milk, cheese, yogurt, ice cream. Don't skip breakfast. Don't have a heavy or late supper. Reduce intake of red meat and chicken, and increase intake of fish. Minimize your intake of lobster and shrimp.