There is more to healing your metabolism then decreasing carbs. This might work, this might help, it might make things worse! *gasp*. Maybe eating more safe starches would be beneficial to this person. We need to stop assuming there is one ideal weight loss diet for everyone, because there isn't. Instead educate them to things that could help them, or they should experiment..but they should focus on how they feel in the process as well. Also some people really do not do well at all on VLC diets(actually the more people I hear about the more common I think this is).. and when they start eliminating fruit, are afraid to eat potatoes or white rice, then probably afraid of some root veggies they are most likely going to be <50g of carbs a day. I would say doing a ketogenic diet for a couple weeks isn't going to be a bad thing..but for 3 months might be for them. So a valid experiment sure, but it can't be shown as the only solution.
There are other mechanisms as well..they could have other problems going on with their body that they really need to focus on healing. Maybe their thyroid isn't functioning properly, or they dont have proper gut flora or gut permeability.
Then there are the psychological factors involved! How you feel towards the food you eat can impact your stress levels..which impact your cortisol levels. You know what can be really frustrating? I found that days where I had a treat/vs days or weeks that I went without one had no difference in my weight loss! Here I was scared to death of eating an apple.. when in fact this really had no impact to me at all.
Also exercise I think is essential to healing/losing weight. If you aren't at least walking everyday and something a little more rigorousness on a weekly basis.. this could cause some imbalances.