Nothing measured before sleeve surgery predicted which women with PCOS lost weight fastest

A study published on September 5, 2026 in the journal Obesity Surgery followed 111 women who had a sleeve gastrectomy and who also had the hormone condition long known as polycystic ovary syndrome, or PCOS. Twelve months after surgery their median body mass index had fallen from 38.5 to 26.7. Their median HbA1c, a blood test that reflects average blood sugar over about three months, had fallen from 5.8% to 5.2%.

Those are strong numbers. The more useful part of the paper is what the researchers looked for and did not find.

Two weight loss patterns, 30.1% and 19.7% of body weight at one year

Rather than reporting a single average, the researchers used a method called group based trajectory modeling. It takes repeated measurements over time and sorts people into groups whose curves look alike, instead of assuming everyone follows one path.

Two groups came out of the data. The faster group, 64 women or 57.7% of the total, had lost 11.9% of their starting weight at one month, 20.7% at three months and 30.1% at twelve months. The slower group, 47 women or 42.3%, had lost 6.6% at one month, 13.8% at three months and 19.7% at twelve months.

Both curves describe real weight loss. A 19.7% loss at one year is not a poor result. But the gap between the two groups is about ten percentage points of starting body weight, and it was already visible one month after the operation.

No preoperative measurement separated the two groups

The researchers then looked back at everything recorded before surgery to see what distinguished the two groups. They report that the baseline characteristics of the two trajectory groups "were comparable across all measured demographic, anthropometric, hormonal, and metabolic parameters." Age, starting weight and body mass index, hormone levels and metabolic blood tests all looked the same beforehand in the women who went on to lose faster and the women who lost more slowly.

For a patient sitting in a preoperative appointment, that is the practical point. In this group, nothing on the chart on the day of the decision indicated which curve a given woman would follow.

Faster losers had lower insulin, C-peptide and LDL at follow-up visits

The faster group had lower fasting insulin at 1, 6 and 12 months, lower fasting C-peptide at 6 and 12 months, and lower LDL cholesterol at 3 and 12 months. At twelve months, LDL cholesterol averaged 2.41 mmol/L in the faster group against 3.02 mmol/L in the slower group.

Insulin and C-peptide are both markers of how hard the pancreas is working to keep blood sugar in range. These differences were measured at the same visits as the weight difference, not before it, so they describe what went along with faster weight loss rather than something that caused it.

The condition was renamed in May 2026

The paper calls the condition polyendocrine metabolic ovarian syndrome, or PMOS. That is the new name for PCOS, agreed in May 2026 through a global consensus process backed by more than 50 patient and professional organizations, including the Endocrine Society.

The reason given for the change is that the old name was misleading. The consensus group states that research shows there is no increase in abnormal cysts on the ovary in this condition, and that the focus on cysts and ovaries contributed to missed diagnoses and inadequate treatment. The Endocrine Society says the condition affects more than 170 million women worldwide, roughly one in eight. The transition is planned over about three years, with full adoption in a 2028 guideline update, so patients will see both names in medical records and research papers for a while yet.