Could you clarify this just a bit? I practice IF for health reasons, so I'm quite interested in learning if it's bunk. I was under the impression that the whole point was that in induces essentially the same effects as CR but without needing to worry about calorie-counting, etc. It's just automatic. Is that what you meant to say? Or are you pointing toward evidence against IF such that people like me who are interested in longevity should consider stopping?
An article about the pitfalls of using mice for animal research leads off with the example of calorie restriction. The controls for calorie restriction mice experiments were obese mice, suggesting that the health benefits of calorie restriction might be conflated with the health benefits of not being obese. I get the impression that people who study calorie restriction still think it worthwhile for life extension, but it's useful to try and integrate all evidence you come across.
[edit] timtyler suggests this is a well-understood effect that's already been taken into account by CR scientists.