To build on the point you started, this paper looks ONLY at weighing less as a contributing factor -- and most dimensions it measures, only a few of the 23 studies selected qualify (for example in the blood pressure category, only ONE study allowed them to determine immediate blood pressure effects from the dieting effort, and ONE other study allowed them to analyze long term changes, and they just threw the other 21 out...) The problem with this approach is that, for example, eating less processed / junk food may correlate very strongly with positive health outcomes but less so with actual weight loss -- think, "If I start eating right and exercising, I may begin improving my overall health faster than I lose fat" -- and then when the fat loss is correlated with the health, it's only a weak correlation, because the two effects are actually the result of a third cause.