A diseasse can be treated and possibly cured. Complications of a disease can sometimes be reversed by treatment.

Diabetes can be cured by a successful solid organ pancreas transplant or by a successful pancreatic islet cells transplant. However, most of the complicatons of longstanding diabetes (cardiovascular, renal, neuropathic and retinal) are usually permanent and even in well documented studies only minimally "reversible" (partial improvement). (Of course the abnormal glucose response can be treated with insulin and reversed by transplant). Panceratic islet cells transplant has been less successful than solid organ transplantation.

Diabetes resulting from obesity can sometimes be treated by weight loss to normal body weight. Whether or not (and to what extendt) the residual complications or damage to blood vessels, kidneys, nerves,and eyes can be reversed depends a lot on how long the abnormal condition was present before successful weight loss. Longstanding diabetes (regardless of etiology) typically results in permanent damage that cannot be reversed.

Thank you Mr.James

But please let me know if it can be reversed through diet. If yes, what type of diet and what would be the mechanism??

I am aware only of weight loss diet to achieve weight loss in the obese patient with diabetes to help correct the abnormal insulin response and glucose metabolism. Weight loss in the obese patient can reverse the abnormal insulin response and can improve the diabetic condition in such patients. However, in the normal weight patient with diabetes, I do not know about any special diet that can correct for the absence of functioning pancreatic beta islet cells that results in the diabetes condition. Occasional websites promote exaggerated claims but these are not validated in peer reviewed medical journals. See and example here:

http://articles.mercola.com/sites/articles/archive/2013/01/07/diabetes-remission.aspx

This paper by Dr. Roy Taylor is a must read on what treatments have reversed Type 2 Diabetes:

http://www.medscape.com/viewarticle/781719

He explains that reversal of DM2 comes down to severe hypocaloric diets (near starvation), large weight loss, bariatric surgery (which uses severe hypocaloric diets before/after surgery) - and this is achieved by the oxidation of hepatic and pancreatic fat stores, which resumes normal function in both liver and pancreas, restoring insulin sensitivity, inhibiting free fatty acid flux, and promoting glucose tolerance.

I would also like to add that the severe hypocaloric method of treating DM2 has been documented (in non-medical literature) to reverse diabetes in individuals that are NOT obese or overweight...