The high insulin and relatively normal fasting glucose sounded so odd to me and none of the LCHF explanations were very convincing with regard to the insulin that I actually searched "elevated insulin normal fasting glucose". There were a ton of hits that addressed this specifically. I thought this one Blood Sugar & Insulin: The Essentials did the best job of explaining in simple terms. Be sure to scroll down to the section on insulin.
This one Insulin Resistance and Hyperinsulinemia is a lot more technical but does a better job of explaining how full blown Type 2 diabetes starts with your body over producing insulin. They call that stage pre-diabetes though.
After reading both those articles, I don't think blaming LCHF for elevated insulin makes any sense at all. If you were to start taking Metformin would your doctor monitor your insulin levels to make sure it was really working? If it brought your insulin levels down quickly it should make weight loss easier. It's also a drug that people stop taking once they have their insulin and blood sugar under control with diet, so it's not like it has to be a long term commitment.