Based on your symptoms, you likely need a diet that manage diarrhoea while providing enough calories to support your exercise, focusing on low -FODMAP, dairy free and easily digestible foods .
Avoid :
Milk, garlic, onions, wheat (gluten), beans, apples, pears, peaches, watermelon,
sugar free gum and candy and fatty fried foods
Includes:
Eggs, chicken, fish , firm tofu
Rice , quinoa, potatoes ( peeled), sourdough bread
Carrots, green beans, cucumbers, lettuce, zucchini, pumpkin
Bananas , blueberries, strawberries, oranges, kiwi
Olive oils, peanut butter, avocados
Gym and Lifestyle :
Hydration:
Drink plenty of water throughout the day but try do not huge amounts
Post workout:
Ensure you have protein to aid recovery such as boiled eggs or shakes
Diarrhoea Management:
If symptoms flare , temporarily reduce fiber intake and stick to white rice , potatoes and plain chicken
Consider a probiotic to help balance gut flora