On my usual band wagon
The 20% number is for T2 diabetics who were not classed by BMI as overweight or obese on diagnosis.
Being at the top end of 'normal' BMI does not, unfortunately, make you 'slim'.
The Newcastle Study suggests that your risk of complications increases for every point you are above the middle of the 'normal' BMI scale, and also says that people who are in the 'normal' BMI range can also benefit from significant weight loss.
Going significantly below the mid range can carry different risks, such as lack of stored fat to tide you over an illness, accident or operation.
I am slowly grinding my way down to a mid range BMI and my BG number are slowly improving but I see no sign currently of a 'cure'.
However if I drop another half stone I think I will be able to really call myself 'slim'.
'Slim' is after all really about your own body image - I thought I was quite trim (BMI of around 25) until I started to take the weight off and then discovered that I really had a pot belly which was getting in the way of simple things like sitting up to get out of bed!
Now I think I am not yet slim enough even though I have lost over a stone.
My waist measurement (true measurement, not waistband size of trousers) is now half my height (so 36" for a six foot male) which is still just O.K. but not spectacular.
It would be nice to get below this and have a bit of a safety margin.
Too much protein can cause issues for some people, so although it is counter intuitive, reducing carbs to the minimum and bumping up the fats can help manage BG because protein does metabolise to produce glucose, just more slowly than carbs.
Cheers
LGC