As to the people not being able to raise their HOMA with exercise and diet
, first we don't know whether diet
or exercise will work until it's tried, that's why it's called a first line attack.
And where it was tried and failed, perhaps their compliance was less than reported, and perhaps compliance may be an unrealistic expectation in some cases. Or perhaps, some as you suggest may simply not react to diet and exercise in terms of reducing HOMA.