There are few things more frustrating than a Bergamasco that just won't eat. In general, I think we worry more than we probably should about how much they are eating. The running joke is that Bergamascos don't start eating until they are three years old and it's actually pretty accurate. It is not uncommon for a Bergamasco to be really thin to the point of wondering if your dog is malnourished. Although there are weight parameters within the standard, many Bergamascos are well below those weights. As long as they are not continuously losing weight or showing signs of illness, it's probably ok.
Sometimes trying too many things in a rush to try to get them to eat can make matters worse. Your dog may just turn it's nose up at anything and go on a total food strike. This can last for a couple of days, but more than that and more intense measures need to be taken. If they go too long without eating, the appetite can continue to dwindle. It's important to feed small and frequent meals even if they won't eat a full meal. This recipe link below is for Satin Balls. This is a raw recipe designed to help a dog gain weight if given in addition to regular feedings or it can be used as the whole meal for a dog that won't eat much else. Sick dogs with appetite loss, or cancer may benefit from the extra calories.
Satin Ball Recipe
Some dogs will go off their food. This means that the food they have been eating all along is now scoffed at. In this case, wait. Wait it out for a day or two and they may resume feedings. If you add something special to their regular food in order to entice them to eat it THIS time, you may find yourself having to add it forever from that point on. Before deciding to switch foods right away, wait and if that doesn't work, you can try to add a little bit of dehydrated liver powder to the top of the food. You may have to do this from now on but it's still better than switching foods all the time if your dog has been doing well on it's current diet.
Dehydrated Liver Trick - You can purchase these from several brands but Stewart's is my favorite. I will shave a cube of liver with a knife over food and they will lick the bowl clean.
Dogs on grain free kibble diets and raw diets will have a harder time gaining weight. If your dog is not allergic to grains, consider Abady dog food for it's high caloric content.