Perhaps it could be altered to read:
"A large number of people on this forum have chosen to reduce the amount of carbohydrates they eat as they have found this to be an effective way of improving (lowering) their blood sugar levels.
The carbohydrates which tend to have the most pronounced effect on blood sugar levels (after straight sugars such as jam, sweets, colas and sugar itself) tend to be starchy carbohydrates such as rice, pasta, bread, potatoes and similar root vegetables, flour based products (pastry, cakes, biscuits, battered food etc) and certain fruits."
My addition in bold.
Sally