This challenges the assumption that the laboratory animals’ unnaturally high calorie intake makes them dissimilar from North Americans. If North Americans consume more calories than optimal, then they are similar to laboratory animals in that way, not different.

This relationship between fat intake and life expectancy does not imply that the study’s findings can be correctly extended to North Americans. The researcher does not say fat intake was examined separately from calorie intake.

This states that some studies with implications for human health do not involve laboratory animals, not that studies of laboratory animals must or usually have implications for human health.

This does not say North Americans who eat fewer calories are tend to live longer—it’s possible North Americans on normal diets are more likely to be long-lived than those on reduced-calorie diets.

This does not specify which type of diet increases longevity or identify the species in question. This may support doctors making some dietary recommendation to increase longevity, but not the one described on the basis of the study.