Fitness will not lead to diarrhea, it may be that you catch a cold after fitness, or eat some food that is not well absorbed.

As you said, food will not cause gastrointestinal discomfort under normal circumstances. If you drink milk, it is likely to cause gastrointestinal discomfort, or it may be gastrointestinal dysfunction.

There are several situations that are prone to this:

1, drink more cold water

Step 2 eat right away

Step 3 go to the air-conditioned room