Not a vet (yet! still in school), but probably medical advice from veterinarians. Only halfway joking, lots of owners are great but lots also will blatantly tell vets that they are wrong, their 8+ years of education is less than the medical advice given to them by some random tiktoker or the kid who stocks shelves at the local pet store.
On a serious note, obesity. Such a large number of animals are obese that people think it’s normal and animals at an appropriate weight are too thin. My SO has even fought me on what the dogs should get to eat vs what he feeds them. It took another vet to tell him that his dog was fat to actually listen to my advice.
A funny, related story. My clinic has hand outs with common treats for dogs like cheese, ham, PB and the human caloric equivalents in donuts. My parents, who are notorious for owning morbidly obese animals, tried to calculate how many slices of ham my dog “needed” to get each day while they were pet sitting because it was “only X number of donuts”. My plan to prevent them from over feeding my dog backfired, she ended up gaining over 5lbs in 3 weeks, which is a lot for a 45lb dog. All of those human snacks and treats really add up.