This sounds like an essay prompt for a health class or something similar. eNotes doesn't allow educators to fully write this kind of essay for students, but I can help get you on the right track. The prompt presents you with a piece of factual information about obesity rates. Next, it asks you a question about society's influence on obesity rates. Your thesis statement for this essay should answer this question. There isn't a right or wrong answer. A thesis statement is an opinion statement that is going to guide your future argument. You could craft a thesis that says obesity isn't a product of society at all. You could argue that the current societal influences are 100% to blame. It is up to you.
I would lean toward arguing that society does influence obesity rates to some extent. I feel that argument gives you access to more supporting data and studies. For example, not every state in the United States requires students to take physical education courses. From my years of teaching health classes, I know that the states with the highest obesity rates coincide with the states that don't require students to take physical education classes. That is not the only societal influence in those places or that exists in any given society, but it is good evidence that shows how obesity rates could be a product of the society that a person lives in. Your job is going to be to find evidence that is specific to the U.K.