[philthewineguy (OP)]

why would a weight loss programme be expected to reduce blood glucose levels in type 2 diabetes?

[alancalverd]

T'other way around. Reducing starch and sugar intake results in weight loss because the body has to burn fat instead.

Glucose In, Glucose Out, to paraphrase a saying from the early days of computing (nowadays it's Policy In, Garbage Out).  So less glucose in, less ends up in the bloodstream.

[Bored chemist]

Or , according to science, rather than Alan...
https://www.nature.com/articles/nature05482

[alancalverd]

So the science agrees with me. Reduce starch and sugar intake ->  reduce adipose tissue -> reduce insulin resistance -> reduce blood glucose! Just as well I read the book,then.

[Bored chemist]

reduce insulin resistance -

That's the important bit which wasn't in your "explanation" and which actually explains the fact that losing weight improves glucose control.

On the other hand, the OP talks about

a weight loss programme

which might mean getting more exercise or reducing fact consumption, yet you somehow read it as

Reducing starch and sugar intake