Maybe the messaging should be "eat healthier"? How many obese people cook for themselves and eat exclusively from the outer aisles of the grocery (fruits, vegetables, seafood, meat, eggs, dairy)?
I could be wrong but I have to imagine the average obese person has a terrible diet. Portion control won't work at that point, you're already doomed to fail.
To be fair, most people have a terrible diet, it's just that some lucky individuals have the metabolism to overcome it. It seems like those people are increasingly the exception and a bad benchmark for how humans should eat.