(A) Older adults generally have slower metabolisms and hence find it more difficult to lose weight regardless of diet plan.
This restates the general assumption about older adults but does not explain why they perform equally well as younger adults on this specific high-protein diet.
Does not resolve the paradox.
Eliminate.
(B) Younger adults tend to be more physically active, which can enhance the effectiveness of any diet plan.
While this is true in general, it does not explain why older adults perform as well as younger adults. If anything, this would reinforce the expectation that older adults would lose less weight.
Does not resolve the paradox.
Eliminate.
(C) Individuals who feel they have struggled significantly with weight for many years are more likely to adhere strictly to new diet recommendations.
This provides a plausible explanation. Older adults, having struggled with weight loss longer, may be more motivated to strictly follow the high-protein diet, offsetting their natural metabolic disadvantage.
Helps resolve the paradox.
Keep.
(D) The new high-protein diet plan was primarily marketed towards individuals who have not previously tried structured dieting.
This explains the target audience for the diet but does not address why older adults perform equally well as younger adults.
Irrelevant to the paradox.
Eliminate.
(E) Most diet plans do not consider age-related metabolic changes when calculating recommended food intakes.
While this highlights a potential flaw in other diet plans, it does not explain why older adults on this particular high-protein diet achieve similar success to younger adults.
Does not resolve the paradox.
Eliminate.
Ans C