No. Stereotypes are not necessarily based on truth. They are more likely based on observations of a limited segment of that population on which the observer jumps to conclusions. Something along the lines of "all the cows in my area are brown, therefore all cows are brown." Then the observer convinces others that their observation is valid and a stereotype is born.
Webster defines Stereotype as: "An idea that many people have about a thing or a group of people that may often be untrue, or only partially true."



Really? And they had all been tested to rule out insulin resistance (which probably 60% of the overweight population has) or thyroid problems?
None of them had stressed Adrenals or PCOS? None of them ever had to take medications that are known to cause weight gain? Wow...you live in a pretty unusual neighborhood.
I'd like to point out that often you can't tell by casual observation whether a person has any of the above health problems; they can only be discovered through blood tests. Often the person who has them doesn't realize it unless their doctor is astute enough to do the bloodwork and verify it.
Sorry, I still don't buy the assertion that overweight people should be treated differently because "it's all their fault" simply because there is no way for the casual observer to determine that so the person treating the overweight person badly is doing so based on a sterotype and jumping to conclusions which are more likely than not....incorrect.

Then again...every good lie has at least a grain of truth in it...that's what makes lies believable.