Dear Himani, as you must be aware that PCOS is a metabolic disorder , which in simple terms means that the body can not handle too much of refined carbohydrates in the diet . In case a person is having too many carbs, then the body hormones become imbalanced, resulting in PCOS.
For losing weight it is important to have a nutrition plan with less carbohydrates, no sugar and higher amounts of proteins. Since you have to lose 20 kilos, which means sustaining a nutrition discipline for few months then you may wish to be under the supervision of a nutrition coach. It is called compliance monitoring which helps to successfully and safely lose weight .