Such studies on dietary intervention are 999 times out of 1000, fundamentally flawed and biased so they're a huge waste of money and resource.
If epidemiologists ever started agreeing on everything, they'd soon put themselves out of a job.
Word of mouth and personal experience are far more valuable. As are empirical studies of illness rates in relation to standard traditional diets where they still exist, e.g. the French paradox.
F 5 ft 3. HW: 196 lbs. Primal SW (May 2011): 182 lbs (42% BF)... W June '12: 160 lbs (29% BF) (UK size 12, US size 8). GW: ~24% BF - have ditched the scales til I fit into a pair of UK size 10 bootcut jeans. Currently aligning towards 'The Perfect Health Diet' having swapped some fat for potatoes.