I was doing some study, and my textbook had some interesting data...
Basically, if you weigh 100kg, and manage to lose just 10kg, you get an average of:
20-25% decrease in total mortality related to obesity (i.e. less likely to die prematurely from excess weight)
drop of approximately 10mmHg in your blood pressure (both values, i.e. if you were 140/90 you would become 130/80 - much healthier!)
>50% decrease in risk of developing diabetes (that's HUGE!)
30-50% decrease in fasting blood sugar value (whether you are diabetic or pre-diabetic)
10% decrease in total cholesterol level, including 30% decrease of triglycerides and 15% decrease of LDL cholesterol.. and 8% increase in HDL cholesterol (the good one!)
So, you can see, it's not all about having a BMI of 20. Just a 10kg weight loss can lead to a MUCH healthier you, if you are obese!
Hope this gives some hope and inspiration to those of us out there over 100kg...