What Could Cause Slightly Elevated Heart Rate And Lightheadedness While Recovering From An Upset Stomach?

Hi I am getting over an upset tummy where I had bouts (but not continuous) diahorrea. Today I woke up feeling much better, no stomach cramps and an appetite so I had a poached egg on toast. Now my heart rate is a little high and I feel a little lightheaded. Is that just cause I have eaten food?