Final answer:
A description of a man who attempted several fad diets and ended up heavier than ever would be a supporting detail.
Step-by-step explanation:
A description of a man who attempted several fad diets and ended up heavier than ever would be a supporting detail. This information would provide evidence and examples to support the main idea or topic sentence of the passage, which is that most fad diets are harmful and ineffective in the long term. By describing a real-life scenario of someone who experienced negative outcomes from fad diets, the author strengthens their argument and reinforces the message that these diets are not a reliable solution for weight loss.