I think you would be able to think more clearly about these topics if you made some additional distinctions among your hypothesis under consideration. Instead of “the Atkins diet is good”, try “the Atkins diet allows me to maintain a lower body fat percentage than the SAD” and “the Atkins diet allows the typical person to maintain a lower body fat percentage than the SAD”. Based on that study, you should decrease your degree of belief in both of these hypothesis, but to a much greater extent for the latter hypothesis relative to the former.
I think you would be able to think more clearly about these topics if you made some additional distinctions among your hypothesis under consideration. Instead of “the Atkins diet is good”, try “the Atkins diet allows me to maintain a lower body fat percentage than the SAD” and “the Atkins diet allows the typical person to maintain a lower body fat percentage than the SAD”. Based on that study, you should decrease your degree of belief in both of these hypothesis, but to a much greater extent for the latter hypothesis relative to the former.