To me it sounds like they did not track change in diet:
> Any personal factors that may have changed over those months—from what each subject ate to the kind of soap they used—didn’t seem to make a difference.
They know that any dietary changes could not have produced a noticeable effect since there was none, but not whether any dietary changes occurred or which ones.
Also, extrapolating from these several-month intervals to "your whole life" can only be speculation.
> Any personal factors that may have changed over those months—from what each subject ate to the kind of soap they used—didn’t seem to make a difference.
They know that any dietary changes could not have produced a noticeable effect since there was none, but not whether any dietary changes occurred or which ones.
Also, extrapolating from these several-month intervals to "your whole life" can only be speculation.