Palpitations and Underweight: Is Exercise the Culprit?

I am working on weight loss and have reduced calorie intake. I noticed I have episodes with them relating to eating, but have not realized a significant pattern. Seem to have them alot in between breakfast and lunch if I have a small breakfast meal. Also Sometimes have them when I eat certain foods. Docs have checked thyroid cause that can cause them. One thing I noticed lately since I do not use ionized salt iodine deficiency can cause them. But I can't get them to test for it. Food seem to effect mine , just don't know how or what yet.