"High starch" refers to a type of food that contains a lot of carbohydrates, specifically a substance called starch. It means that the food item is rich in carbohydrates and can provide a lot of energy when consumed. Full definition
On the other hand, you need to avoid potatoes, vegetables with high starch content, rice, pasta bread (including muffins, cakes and the like). (onketosis.com)
They may also use carbohydrate sources with high starches that can cause weight gain. (dogfoodinsider.com)