Sorry if I appear a bit stupid but I don't understand this. I know there are people on here with T2 who are slim, and were slim when they were diagnosed. So, although there is the common link with obesity, where do they fit into your thinking?
Most people use bmi when talking about weight and diabetes, but this is misleading, the important thing is bodyfat, and bodyfat, can be divided into several categories, but the most dangerous one is is visceral fat, and subcutaneous is the good healthy fat.
So you can still be defined as having a healthy bmi, and still have a very high bodyfat. My favourite example is this indian diabetes professor. All his patients underwent a bodyfatscan, and himself and his colleague did this, and here were the results.
http://img.medscape.com/slide/migrated/editorial/cmecircle/2005/4915/images/yusuf/slide016.gif
Despite having the exact same bmi 22-23, the one to the left has 9.1% percent body and the one to the right, the indian professor has a bodyfat of 21 %, double the amount!
here is an newyork times article showing the mismatch between bodyfat and bmi
http://www.nytimes.com/interactive/...n-is-bmi-misleading?smid=tw-nytimes&smtyp=cur
Takeway figures :12 % of overweight men had less than 25% bodyfat, 6% of men had a normal or underweight bmi but more than 25% bodyfat!
Women, 3% of woman had under 35% despite being overweight, and 15% of women where of underweight or normal bmi, but had more than 35 % bodyfat.
These are quite staggering figures in my mind.
http://i2.nyt.com/images/2015/08/28/science/bodyfat-bmi/bodyfat-bmi-jumbo-v2.png
This professor has devoted his life to understanding why indians get diabetes at a lower bmi than us westerners.
Two lectures by him.
Look at these strikening differences in visceral fat between people with type 2 diabetes and non-diabetics. The diabetics has much more white fat than the nondiabetics.
http://www.hivehealthmedia.com/wp-content/uploads/2010/10/visceral-fat.jpg
Liposuction removes the subcutaneous fat, not the visceral fat, some of the goody fat is gone but the dangerous remains.
http://img.medscape.com/slide/migrated/editorial/cmecircle/2005/4005/images/sharma/slide015.gif
And here are the results
http://img.medscape.com/slide/migrated/editorial/cmecircle/2005/4005/images/sharma/slide016.gif
No difference.
Example of two boys with same bodyfat, the one with more visceral has prediabetes
http://img.medscape.com/slide/migrated/editorial/cmecircle/2005/4005/images/sharma/slide010.gif
Luckily when you lose fat, it is the visceral fat that is the first go , but people differ even here on how much of they lose:
http://drrajivdesaimd.com/wp-content/uploads/2013/07/visceral-fat-1.jpg
this guy lost over 13% of bodyweight, but over 34% of visceral fat! That was more than 3 litres of visceral fat
http://img.medscape.com/slide/migrated/editorial/cmecircle/2005/4005/images/sharma/slide026.gif
Here a 10% weightloss resultet in 30% reduction visceral fat
And this fat is not necessarily seen by looking at people, here is a striking example:
https://upload.wikimedia.org/wikipe...onal_Image_of_a_TOFI_and_a_Normal_Control.jpg
Same bmi,gender,age and bodyfat, the control has 1.6 litres of itnernal fat, the unhealthy one has nearly 6litres!, a factor of over 3 in difference!
Another example
https://en.wikipedia.org/wiki/File:..._in_men_with_the_same_waist_circumference.jpg
Same waistsize, of six people, the one with least has 0.5 litres of internal fat, the one with most 4,3 litres.
Michael Mosley is also an fine example, in his fasting documentary on bbc it is shown that he has nearly 30 percent bodyfat, but only slightly overweight in bmi. When he lost his fat, all of his sugars improved, his father died of diabetic complications!
http://www.theguardian.com/lifeandstyle/2013/may/12/type-2-diabetes-diet-cure
This is a very skinny journalist from the guardian that got diagnosed with diabetes type 2. He lost over 10 kgs, and his diabetes disappeared, he used to keep a blog and he was undiabetic as of 2015 september, and got rid of his diagnosis in 2012. You could also email and ask him.
So in short, genetics do matter, your bmi may be normal but you can carry loads of "wrong fat" and get diabetes despite having a normal bmi.
My own family story shows this. I have myself been over 40 kg heavier than now, but my sugars were perfect. I got myself tested at the doctors because of worry about it. My mother has bmi of over 40, but she does not have diabetes, I make her check her sugars regarly because of my worry. My aunt is also very obese, not as much as my mother, but she got diabetes. her bmi is maybe 35, my mothers 40, and my mother is the more "healthy" one. My dad is 174 cm, and used to weigh 95 kg, he is now 69kg. He is a proffesor of medicine, but has never had any bad sugars. My dads new wife however, is a nurse, and looks very skinny, her father is as well, but they both got diabetes. My guess is that they have loads of visceral fat and if they lost 5 kgs each they would be cured.
Ask any more questions if you are wondering about something.