Hello,madam most of the times gestational
diabetes disappear once the delivery happens,, and then you will become normal later,,, even normal pregnancy itself causes weight gain dye to growing baby and due to hormonal imbalance. So don't worry much for future diet now. You need to control your suger level for now,, you may need medicine for that,, avoid all sweets,, extra suger, rice items or any foods with carbohydrate should be minimal quantity,, eat more protein containing, pulses and vegetables.