Is PCOS weight gain always dangerous? We asked a doctor

Polycystic ovary syndrome (PCOS) is a condition which can cause irregular periods and decreased fertility. All women produce “male” hormones (androgens), but those with PCOS have higher levels of androgens, which can affect the menstrual cycle. PCOS often runs in families: someone’s risk of PCOS is five times higher if their mother had PCOS. However, genes do not tell the whole story, and other factors such as diet and lifestyle are thought to play a role in the development of PCOS.¹

Every month, the ovaries make a structure called a “follicle”, which releases the egg that has been developing during the course of the month as well as male hormones. In PCOS, the ovaries produce many small follicles as opposed to one big one. This can cause irregularities in hormone levels which mean that ovulation does not occur every month (sometimes called an “anovulatory cycle”). This can make it more difficult to become pregnant.

Anovulatory cycles can make the lining of the womb become thicker, leading to irregular, heavy and/or prolonged periods. Sometimes, the womb lining is thin and there are no periods at all. The high androgen levels can cause other symptoms such as excessive facial hair growth, acne, and hair thinning (sometimes called androgenetic alopecia).

What has PCOS got to do with weight gain?

Weight gain is common in PCOS, although not everyone with PCOS will gain weight. Estimates vary, but the majority of people with PCOS are either “overweight” or “obese” (meaning they have a BMI over 30).² The reasons why PCOS is associated with weight gain are not completely understood.

Insulin resistance is one factor which may contribute to weight gain in PCOS. Insulin is a hormone produced by the body which helps cells to process sugar. Most people with PCOS have insulin resistance, which means that the cells of the body do not respond as well to insulin.³ In response, the body often produces more insulin to ensure that cells process sugar appropriately. The high amounts of insulin will act on the adipose tissue (fat cells) stimulating it to produce more fat and stopping fat breakdown.^4,5

Obesity is associated with a wide range of harmful effects on health, and these can affect people with PCOS who are obese in the same way

The high level of male hormones seen in PCOS also seem to impact the way that fat cells work, and also the distribution of fat within the body. However, there is limited research on fat cell functioning in PCOS.⁶ However, people with PCOS, even those who are not overweight/obese by BMI, are more likely to have higher amounts of fat distributed around the abdomen.⁷

Is this extra weight dangerous?

Obesity is associated with a wide range of harmful effects on health, and these can affect people with PCOS who are obese in the same way. These effects included an increased chance of osteoarthritis, gallbladder disease, non-alcoholic fatty liver disease, gastroesophageal reflux, hypertension, depression, sleep apnoea, and increased susceptibility to infections.

However, being obese and having PCOS can make some obesity-related problems worse, particularly ones related to your hormones. Those with PCOS and obesity are at increased risk of diabetes because of the insulin resistance and are more likely to have high levels of “bad” cholesterol in their blood.

A combination of diabetes, increased bad lipids, and high blood pressure leads to a greater risk of coronary artery disease, stroke, and blood vessel disease, a combination known as metabolic syndrome. People with PCOS and obesity are more likely to have metabolic syndrome: a review paper of 46 different studies found that about 30% of women with PCOS had metabolic syndrome.⁸

There has been some suggestion that obesity in people with PCOS leads to increased cancer risk, but the evidence to date is limited

There has been some suggestion that obesity in people with PCOS leads to increased cancer risk, but the evidence to date is limited. A review article found that women with PCOS were about 2.8 times more likely to develop endometrial cancer than those without PCOS.⁹ However, the review found no clear association between PCOS and breast or ovarian cancer.¹⁰

In terms of the other symptoms of PCOS, such as irregular periods, high androgen levels, and excessive hair growth, there is no clear relationship between obesity and these symptoms. However, weight gain is associated with difficulty in getting pregnant and reduced efficacy of fertility treatments.^11,12 It is also associated with increased complications in pregnancy such as high blood pressure, gestational diabetes, pre-term labour, and infant death.¹³

At what point does weight gain start impacting health?

There are no grading systems specific to PCOS in terms of what level of weight gain is dangerous. However, in the general population, a body mass index (BMI) over 25 is considered “overweight”, and over 30 is considered “obese”. The negative health effects can occur from 25 upwards and the higher the weight, the worse the risk.

While using BMI does have its flaws, it is a useful indicator when it comes to determining what sort of weight is roughly healthy for you. If you are starting to notice health problems associated with weight gain, such as joint pain and breathlessness on walking, or any newly diagnosed problems such as diabetes, and your BMI is above 25, it may be worth consulting your GP about whether you could benefit from weight loss.

How can I lose weight if I have PCOS?

There are different ways to help treat excess weight or weight gain in PCOS. These include lifestyle changes with both exercise and dieting, although exercise alone is not usually effective.¹⁴ Medications such as metformin, which helps with insulin resistance, can sometimes be used.¹⁵

Orlistat is a drug that blocks an enzyme in the gut preventing fat absorption, leading to weight loss. But this can also cause fatty stools and gas, so some people prefer to avoid taking it. A research review found that Orlistat was associated with weight loss in women with PCOS, although not a reduction in waist circumference.¹⁶

There have been some studies that have reported that bariatric (weight loss) surgery can have a beneficial effect on some symptoms of PCOS such as irregular periods and excessive hair growth, although studies are generally small and limited in number.^17,18

Weight reduction can also have a positive effect on general health and reduce the risk of conditions like diabetes and high blood pressure. However, weight loss surgery comes with the risk of complications and often involves dramatic and long-term changes in eating habits. If you have concerns about your PCOS-related weight gain, it is important to discuss these with your GP so they can recommend the best course of treatment.

Featured image is of a person sitting down, with their hands clasped on their lap. Only their torso is visible in the frame, against a pale pink background that has a palm-tree pattern on it

Last updated February 2024
Next update due 2027