This doesn’t differentiate the French from North Americans. In addition, we already know the French eat just as much fat as North Americans. We have no reason to think that higher rates of fat consumption in the past have any impact.

If this has any impact, it deepens our confusion. If other diet factors haven’t been linked to heart disease, then it’s harder to explain the discrepancy by pointing to a difference in other foods eaten by the French and North Americans.

This points out a difference between French and North Americans that could explain the French people’s lower heart rate. They only recently reached the same level of fat consumption as North Americans, so the French’s heart disease rate may not have had enough time to rise.

We’re trying to explain the discrepancy in heart disease rate. Lack of difference in rates of other disease doesn’t help explain why the French have a different rate of heart disease from North Americans.

This deepens our confusion, because it would lead us to expect the French to have a higher rate of heart disease than North Americans. But they actually have a lower rate.