I wish someone had told me, when I was starting out, to forget everything I thought I knew about what a "healthy diet" is. Sure, lentils are lower in carbs than some things which are very high in carb, but lentils are still high carb items of themselves, and when eaten, we tend to eat them in some quantity. Probably OK for many people but not for those of us with a metabolic syndrome issue.
One of the things you need to unpick is that certain foods have been given a "healthy" (or "unhealthy") aura, largely by the media printing press handouts, and it simply usually doesn't get questioned.
Friends of mine were horrified that I was eating butter, red meat, cooking with lard, and not eating bread, oatmeal, fruit, etc. and were sure I would become very sick indeed. Bit sheepish now. I had a discussion with a family member (recently) who has just been told he has high blood glucose - he claims to have forgotten what the actual figure is. Despite seeing me normalise my BG levels and lose more than six stone in the last five years, he will not accept that what he eats is anything to do with his problem. He's determined to go on eating what he's told is "healthy food", full of carbs.