Passage Summary: Sports foods are basically just overpriced versions of regular food. Since they don't offer better nutrition, the only reason anyone would buy them is because of expensive marketing campaigns.

Conclusion: Advertising is the primary reason athletes purchase expensive specialty sports foods.

Reasoning: Specialty sports foods contain the same nutrients as common grocery store foods but cost two to three times as much.

Analysis: The author assumes that because the nutritional content is the same, there is no 'rational' reason to buy sports foods other than being swayed by ads. To weaken this, we need to find another practical benefit of sports foods that justifies the price. For example, maybe sports foods are much more portable, have a longer shelf life, or are easier to consume while running than regular food. Look for an answer that provides a non-advertising reason why an athlete would find these products valuable.