Remember the movie wall-e? All those fat people on the ship, we're going to end up like them if we don't tackle the root problem. A cure for type II diabetes is great and all, but it does nothing to solve the root problem(s).
This is an echo-chamber response: someone on the internet heard something, and keeps repeating it. It's rooted in emotional superiority, and comes from someone with no background in scientific research or statistics.
All attempts to pin obesity on the "that sounds about right" reasons have failed, including exercise and food intake - for both amounts and types of food.
In particular, lab animals grown today are fatter than the ones grown decades ago, despite having the same (and well-documented) diets and exercise. (Source.) Same with pets.
Current opinion holds that there is something in the environment that causes obesity - some agent that wasn't pervasive a couple of decades ago. Over 700 possible causes have been suggested, including your favorite bugaboo (whatever that is). We're slowly going through the options looking for the cause.
No diet will work, even that great "miracle cure" you heard about on Oprah. Lack of exercise doesn't cause it. Diets and exercise regimes work for *some* people because in changing their behaviour they eliminate the causal factor inadvertently - without knowing what it is. It wasn't the diet and it wasn't the exercise.
Try to keep current with scientific theory, otherwise we'll be repeating these old wives tales forever.