I think the substance is that there are plenty of people who change their weight permanently. On the other hand the evidence for particular interventions isn't that good.

None of those address permanent weight loss per se. They all address the more specific problem of permanent weight loss through dietary modification. A successful approach to weight loss would incorporate a change in diet and exercise habits along with an investigation of the 'root cause' of the excess weight i.e. the psychological factor that causes excessive eating (Depression? Stress? Pure habit? etc.) I also question your implicit premise that "If it ain't permanent it ain't worth doing". That sounds like a rationalization to me. For a woman who's 25 and looking to maximize her chance of reproductive success (finding a mate), 'just 5 years' of weight loss would be extraordinarily superior to no weight loss. Permanent weight loss would be only marginally better.