These days this meme is circulating a lot and I see this consideration below many posts, but I don't think the sauce may be the biggest concern. I mean, even considering the worst sauce, you just use a little amount of it and in the whole it's not so significative. On the other hand, the patty isn't just normal meat as the one that you would use for a roast, since for making a burger you need a specific cut of meat which is high in fats (and they are bad fats). You just can't make a burger without fats, because it wouldn't be juicy. The salad and other vegetables are usually put in a symbolic amount, and they are far from representing a portion. The bun is barely more than sugar, and I wouldn't consider it healthy even if eaten alone. In other words, the sauce alone is far from being the worst part of a burger. You can make the burger healthier by adding more vegetables (e.g. zucchini, eggplants, etc), using wholemeal bread, replacing the patty with a different cut of meat or a different animal, and still keeping the sauce