Just posting this as it really surprised me and thought I'd share in case anyone else is interested.
I've recently been seeing a cardiologist, who is on Tatler's top doctors list. I am overweight, with high blood pressure and basically said "I know I should eat less and lower fat, but I do find it really tough to stick to".
She told me that the 2 diets with the best clinically-reviewed, robust evidence of effectiveness and health benefits are firstly the Mediterranean diet and secondly, surprise surprise, low carb. I almost fell of my chair.
I've done low carb in the past, got disheartened by being told that is unhealthy, over and over again, by my GP, stopped and piled the weight back on.
Apparently the whole "a calorie is a calorie" thing is rubbish - some foods (nuts I think were one of them) don't appear to have any impact on weight even if 500 cals or so are simple added to the same person's diet daily, but sugar is usually the biggest problem for most people - and can have an effect on the brain similar (as seen in a functional MRI scan) to hard drugs.
I'm sure lots of people will disagree - but I thought it was really interesting...