Considering the ingredients in Gusto i'm not surprised it's not a food that put's weight on easily,the contents probably get pooped straight out

;)
gets about 50 g of dry food twice a day!Goldmali is that a typo?

Luvhandles it sounds like the 200g recommendation is for 'fresh' food,not dry food. That is the same amount recommended when feeding a homemade diet for a dog your size :)
Your right,different foods have different feeding guidelines,i would say the average amount for a dog your's size would be between 100and150g,but again it depends on which food and how digestable it is,the worse the food the more they need to eat to get the correct amount of nutrition.