Well, a couple of issues here - nutritionists aren't scientifically trained, but dieticians are:
https://www.healthcareers.nhs.uk/explore-roles/allied-health-professionals/dietitian
And I'm following the LCHF because it's
better science than the old science that's now pretty much show to be wrong. That's the way science works, when it works well - it's constantly improving itself, questioning its beliefs, keeping open minded. That's why I always hear alarm bells when people big up an alternative therapy that's based on some ancient philosophy.
There is a very good evidence that the LCHF diet works and that the fears about eating more fat are not based on good evidence. One of the problems that is often encountered in all sciences is that people have entrenched positions - and are often unwilling to throw out those ideas even when the evidence mounts that they're wrong. Richard Dawkins tells a very good story of how it should happen:
“I have previously told the story of a respected elder statesman of the Zoology Department at Oxford when I was an undergraduate. For years he had passionately believed, and taught, that the Golgi Apparatus (a microscopic feature of the interior of cells) was not real... Every Monday afternoon it was the custom for the whole department to listen to a research talk by a visiting lecturer. One Monday, the visitor was an American cell biologist who presented completely convincing evidence that the Golgi Apparatus was real. At the end of the lecture, the old man strode to the front of the hall, shook the American by the hand and said - with passion - 'My dear fellow, I wish to thank you. I have been wrong these fifteen years.'”
However, for various reasons, some science, and I think especially medicine, doesn't always work like this, it took years before older doctors started believing that stomach ulcers were caused by the Helicobacter Pylori bacteria and started treating it with anti-biotics. One practical problem is actually getting all the new information out to doctors - they have textbooks written years ago and simply don't have the time to keep up to date with all the new experimentation. Unfortunately, you have a political situation where the 'Old Guard' are the ones in charge of policy and guess what they believe.
By the way, the jury's still out on LCHF diet - there is NOT a consensus yet, we don't know all the mechanisms involved, we don't know the long term effect of this diet on the human body - we have some anecdotal evidence from people who have had some success so far with it, but have you seen what happens on here when people argue against it? They face a sh!tstorm of opposition. It's not the only answer to diabetes - people have conducted trials of various other diets that have effected weight loss and reduction in BG levels - including a 50% carb diet.
Personally, I'm convinced that FOR ME, the combination of this diet and exercise I've been doing is currently effective at keeping my BG down and against all the received wisdom, is improving my cholesterol too. I wouldn't say that this is useful data, but as it works for many people I'd imagine some well-constructed studies could and should be done to find out more.