Glycemic index means nothing. Cake has a low glycemic index (someting like 30, depending on fat content). Oatmeal has a higher glycemic index (55). Does that me

Glycemic index means nothing. Cake has a low glycemic index (someting like 30, depending on fat content). Oatmeal has a higher glycemic index (55). Does that mean we should stop eating oatmeal and substitute it with cake?