Read the labels. They are there for a good reason. Simple carbohydrates break down very quickly in the body. They will cause large amounts of insulin to be released into the bloodstream. Blood sugar levels are elevated very quickly.
Many people get shaky during the day.
This is mainly because they skip meals and then eat the wrong kind of food. This roller coaster ride can become a very viscous cycle. Over a period of time, left unattended, it can lead to major health problems. Adult onset diabetes is a result many times of poor nutritional choices growing up. Many diabetics are overweight.