My personal belief, based mainly on my own experience, is that everyone's metabolism is different; and any attempt to define which diet "will work best" for everyone is idiocy.
When I was diagnosed with with diabetes, I was about 10 pounds overweight. After a year of following the diet the nutritionist / dietician prescribed for me (and pretty religiously, mind you), I was 40 pounds overweight. In addition, my A1C, cholesterol, and triglycerides skyrocketed, despite my having been placed on Lipitor, metformin, and glypizide.
This went on for several years and several dieticians, all of whom prescribed their own tweaked takes on the ADA diet. I also went out and bought a gym and treadmill (and actually use them), but the weight stayed. They gradually lowered the daily caloric intake to 1,200 calories, but my weight stayed the same. Finally, one doctor put me on a drastic 600 calorie / day diet for two weeks. I didn't lose a pound.
After I got tired of listening to advice that didn't work, I told all the dieticians their services were no longer required and I went on Atkins. I'd tried it off and on over the years and always lost weight, but the doctors and the dieticians screamed at me about it, telling me all kinds of horror stories about how it was going to kill me. But the "balanced" diet they prescribed wasn't working, either; so I fired them all and told them I'd do it my way, and if I dropped dead, I wouldn't hold them responsible from the grave.
That was about two years ago. I've lost about 35 pounds since then. At my last physical, all my labs were in normal range for a person without diabetes. My blood pressure also went down to 118/ 70, which is about what it was when I got out of the service. This next physical coming up I may ask the doctor to drop the Lipitor and glipizide and see what happens, depending on how the labs look. And if he says a word about seeing a dietician or going off Keto, I will fire him. The most recent iteration of my BC/BS policy doesn't require me to have a PCP. Should he say a word about how unhealthy Keto is, I will promptly fire his ass.
All that being said, I don't "recommend" Keto. I don't have the credentials to be giving dietary advice, and I've been through this **** too long to recommend anything for everyone, even if I did had the credentials to do so. What I do know is that no diet works for everyone, and anyone who pretends otherwise is a moron. What I care about is what works for me -- and damn the ADA and the whole dietician profession if they don't like that.
Rich