How effective is metformin for ovulation in pcos women that are not diabetic or overweight?

Should help. Metformin is often first line treatment for pcos, even in women who are not overweight and don't have diabetes. Insulin resistance is usually still a component of pcos which contributes to the menstrual and hormonal irregularities. Metformin increases Insulin sensitivity which is the reason it is such a good medication for pcos.
Not Very. For most women, metformin is no longer considered the first treatment used in pcos women. Actually, there are concerns that it ls less effective than other therapies and may actually increase risk of miscarriage when used alone for ovulation induction. In appropriate pcos patients, it can be useful for other reasons. At this point, most studies shows Clomiphene is the preferred therapy.
Metformin. The study suggesting metformin is not of value did not use the generic which is more effective. It did not advise combining metformin with diet and exercise. The majority of women I see have not been advised about diet and usually are taking far too little mediation.