The extra energy that is required during pregnancy is only 300 kcal/day and any consumption above this will only add empty calories and weight to the mother. This is only about 15% more than usual Indian food quantities.
While the common Indian advice is to eat for two, we must keep in mind that it is not two grownups we have to eat for. It is for a baby that is 3 - 4 kgs in weight. So focus on nutrition, rather than the quantity of the food you eat.
See the article below for how to plan your meals during pregnancy and what foods provide the right nutrients.
If you are having multiple babies or have a special health condition, please talk to your doctor about your nutritional needs.