Having your body weight under control helps in controlling diabetes. This finding is, however, not new. Here is a 2011 study [0] using the same 600 calorie/day diet. This study only had 11 people, the current study [1] has 298.
By reducing the calorie intake you lose the fat/weight, afterwards you can resume a normal diet. The calorie restricted diet seems to restart the pancreas, kicking in the insulin production. If you can maintain your weight you are good, else you will eventually have to go back to medicine. Guardian report on the 2011 study [2].
A reddit AMA with Roy Taylor of Newcastle University [3]. Previously discussed on HN [4].
[0] : https://link.springer.com/article/10.1007%2Fs00125-011-2204-...
[1] : https://www.theguardian.com/society/2011/jun/24/low-calorie-...
[2] : http://www.thelancet.com/journals/lancet/article/PIIS0140-67...
[3] : https://www.reddit.com/r/IAmA/comments/47psga/iama_hi_im_new...