I disagree. Obesity is not the cause. It is a symptom of an unhealthy, carb-laden diet. The standard American diet: carbs and grains heavy with inflammatory vegetable oils is the direct cause of most chronic diseases.
The natural progression of our lives is not to be constantly sick. In a very real sense, we are what we eat.
Obesity is the result, but it is a primary indicator. Metabolic Syndrome, and Insulin Resistance.
There’s all sorts of maladies that go bye-bye almost like magic, when the fat gets burned away. It also improves blood pressure and “good” cholesterol blood parameters, allergies, arthritis, and is important for a healthy immune system. Ever notice there are no really old fat people? All of the super long lived people are always pretty spry. They often drink, and smoke too, but let’s not get carried away. There’s also just plain quality of life issues, being able to do everyday things, to say nothing of not being chained to a huge pile of prescription pills.