Your body may not like the fat and grease found in the hamburger or any other fast food hence the diarrhoea!

If you have hemorrhoids the straining of the bowel may make these bleed due to the pressure being placed upon them.

You could also be intolerant to some food e.G. Dairy, wheat, etc.

Make an appointment with your doctor to rule out any serious problems, i'm sure you will be fine if you change your diet and adopt good eating habits.

All the best to you.

I agree with blinkybill!