seren nos - It's not just about weight loss as many people with auto immune diseases such as fibromyalgia and rheumatoid arthritis have seen benefits. Believe it or not, stuides have shown cholesterol levels and blood pressure to come down as a result, even though the regime recommends fat as a fuel source rather than carbs.
KateF - Yes, the fat burning thing does make complete sense but like you, I am retiscent to give up my gels. I have tried date-based fruit bars on long runs and they seem to have quite a good effect.
Curly 45 - I agree that anyone considering this should do it gradually. My diet for example is 'healthy' but very much carb based and I haven't yet tried to eliminate sugar as I think it would be incredibly difficult!