It's not entirely an illusion. Some patients do succeed in making lifestyle changes that cause type 2 diabetes to go into remission. But the best results have been achieved with healthcare providers actively helping patients make dietary changes on a frequent basis.

https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

https://link.springer.com/article/10.1007%2Fs13300-018-0373-...