And that right there is the point. The symptom is obesity, and over-weight. Why is "over-weight" a problem? Because it is the indicator of a whole host of long-term health problems... like heart disease, and cancers, and diabetes, etc. And the list goes on. The "over-weight" is a symptom of something else that's "off"... the DIET. But we can't get "people" to have the willingness to improve their diet... so we treat the symptom, with a drug.
All of us on CT know that it doesn't really matter much what the genetics of a critter is... if we can get them to consume enough "energy", we WILL be able to fatten them up... some more than others genetically. But ALL will fatten, with the right diet consumed in enough quantity... unless they're sickly. How will we entice them to consume more energy? By using the same tactics that food manufacturers use to get consumers to consume more of THEIR products... sugars in various forms, and concentration of energy per bite via sugars (use lots of grain like "corn"... high starch, which is converted into sugars... instead of grasses, for example). It doesn't have to be healthy, it just has to be enticing. Blend a little molasses into a feed that's otherwise not so enticing, and the cattle will devour it. (And shouldn't we be asking ourselves... is it really "healthy" for our animals to be "fat"? And should I be choosing to eat an animal that would qualify as "fat/obese", or would I be better off consuming a critter that's "excellently fit", and "the picture of health"?)
THAT is what is wrong with our diet today. It's not "nutrient dense", but instead, it's "calorie dense and starch and sugar dense". And few are willing to have enough initiative and willpower to change that for themselves. Many are unwilling to even admit that they have a problem. Instead, they'll just "take a pill" or "a shot", and WOW, I lost weight! VOILA!