Okay, I get that part. I admit I'm not sure if that's meant to contradict anything I said, or agree with it, or add to it, or state the same thing but in more accurate terms, or what. In case there's any confusion, my point before was that justifying discriminatory behavior (of any kind) towards heavy people by saying "they brought it on themselves, so it's cool to make fun of them" doesn't really work, because overeating isn't the only cause of weight gain, and even if it were, making decisions that have negative consequences doesn't invalidate a person's feelings.
Taking your point--that overeating is a major cause of weight gain, particularly in the United States--into consideration in that context, it would appear to be a modification of, but not a contradiction to, the statement "overeating isn't the only cause of weight gain". I may be missing something, but that's what I'm taking from it. Does that sound right?