Passage Summary: A scientist points out that lab animals live very sedentary, well-fed lives, which might make them poor subjects for health studies that assume the animals start off in a normal, healthy state.

Conclusion: The conditions under which laboratory animals are kept can negatively impact the accuracy of research results.

Reasoning: Research subjects are assumed to be healthy, but lab animals typically have high food intake and low exercise, and caloric restriction studies specifically assume subjects were not previously overfed.

Analysis: The argument hinges on a gap between the lifestyle of lab animals (overfed and sedentary) and the requirement for research (healthy subjects). For the scientist's conclusion to work, there must be a link between these lifestyle factors and a lack of health. We should look for an answer that suggests animals with ample food and little exercise are not truly healthy. If these animals could be both overfed and healthy, the research results wouldn't necessarily be 'skewed' as the scientist claims.