Hi Tony, my other half (he's the diabetic one not me) was pretty thin when he was diagnosed ( just under 11 stones) and as far from your typically described type 2 as you could get (healthy diet, plenty of exercise), his BG levels are all over the place and since he was diagnosed he's lost lots of weight unintentionally. He's on a very low carb diet but it certainly isn't low calorie. He eats over half a kilo of nuts per day, has snacks, has coconut milk, cheese, lots of oily fish etc. his total calorie intake per day is almost three times the recommended amount for a man yet he still loses weight (8 stones 8 pounds this morning).
I think there's probably more people around who are thin and diagnosed type 2 than we realise but public health bods tend to push the image that all type 2s are overweight.