PCOS (polycystic ovary syndrome) is a hormonal disorder that usually involves having high testosterone and/or insulin levels. Though testosterone is needed for the first stage of egg development in the ovaries, having too much of it can be a problem. High testosterone causes lots of premature follicles (the sacs that hold eggs) to get recruited in the ovary each cycle, but then, because there are way too many of them, their growth gets shuts down. This creates a whole bunch of follicles (the “polycystic” in polycystic ovarian syndrome), with none being able to grow and become a mature egg.
Adding to the issue is the fact that 65 to 70 percent of people with PCOS are insulin-resistant (more on this below). Insulin helps regulate blood sugar, but when cells stop responding to insulin, you wind up with too much circulating in your blood. Again, too much of a good thing can cause issues: excessive insulin tells the ovaries to make even more testosterone.
These factors can lead to people with PCOS having really irregular or long cycles (making it important to track ovulation if you have PCOS), and they may or may not ovulate. Since high insulin levels are a major culprit, one of the goals when treating PCOS through lifestyle is to focus on insulin regulation to make the body more sensitive to this hormone and bring levels back to normal.
What is insulin resistance and how does it relate to PCOS?
Insulin is like a gatekeeper that allows glucose (sugar) to enter a cell. When you eat sugars or carbohydrates, that sugar signal tells your pancreas to release insulin so it can get to work. Insulin gets pumped into your blood where it can then start pushing the buttons on your cells that open the door to allow glucose in. But when you consume excessive sugars and carbohydrates, your pancreas starts working overtime, pumping out more and more insulin.
The problem is your cells can become immune or resistant to this signal over time, so when you have chronically high insulin (regardless of your blood sugar levels), it’s called insulin resistance.
Insulin is supposed to do a job and get out of the way, but when high amounts stick around in your blood it can start telling your body to pack on extra adipose (fat) tissue around your mid-section, and it can travel to your ovaries and directly influence your cycles and egg development.
Since insulin can cause weight gain, it also sets off other hormonal effects; adipose tissue isn’t just fat on the body. It contains hormones and enzymes that convert hormones, and can be used as a place to store things like toxins. For example, excess adipose tissue increases the activity of an enzyme called aromatase which converts testosterone into estrogen, leading to poor testosterone and estrogen balance. This is one of the reasons why obesity can cause infertility: it disrupts the normal hormone balance (while creating inflammation).
That said, not everyone with PCOS will struggle with obesity. It’s completely possible to be lean and have insulin resistance, but that high insulin will still act on the ovaries and interfere with egg development. So in some cases of PCOS, regulating insulin and reducing insulin resistance will be a main goal, whereas in other cases this could be paired with a focus on reducing obesity. A low-carbohydrate diet or ketogenic diet could be helpful in cases of both obese and non-obese PCOS as a way of decreasing insulin levels and improving insulin sensitivity.
What is a keto diet—and can it help PCOS?
The keto (short for “ketogenic”) diet promotes consuming more fat and less carbs, while ensuring adequate protein intake. The rationale is that this approach pushes the body to use fats as fuel instead of carbohydrates. But this isn’t as easy as flipping a switch. Your body wants to use carbohydrates as its primary fuel source, and it struggles to make the change. To force the switch in energy-making strategies, you need to consume less than 50 grams of carbohydrates per day. As such, a ketogenic diet typically consists of at least 80 percent fats and 5 percent or less in carbohydrates (about 30 grams per day).
Using fats to make energy, instead of carbohydrates, requires the liver to take those fats and break them down into ketone bodies, hence the diet’s name. Those ketone bodies are what your cells can use to make cellular energy (called ATP). Using these ketones as fuel can help reduce obesity and improve insulin regulation because it cuts the need for the alternative energy source: sugar-loaded carbs.
In one study, 24 participants who were overweight (defined as a body mass index (BMI) over 25) and had PCOS with insulin resistance were instructed to follow a Mediterranean-style ketogenic diet, consisting of 1,600 to 1,700 calories per day. By 12 weeks, participants lost an average of 20 pounds, had significantly lower BMI scores, significantly lower insulin and testosterone levels, and improved cholesterol levels.
That said, following a keto diet where 80 percent of your diet is fat-based can be really hard and may not be doable long-term. Following a low-carbohydrate diet consisting of about 40 percent carbohydrates, has also been shown to improve weight loss and insulin sensitivity and can lower testosterone levels in those with PCOS. If going keto is too tricky, you can still have a positive effect on insulin and blood sugar regulation by going low-carb.
How does a keto diet impact fertility and pregnancy?
There are currently very few studies on the keto diet’s effect on human fertility, but we do know that it’s not recommended nor safe during pregnancy, and eating keto too soon before conceiving can even cause issues.
One animal study found that following a ketogenic diet right before and during pregnancy led to lower fertility and smaller litter sizes. These little pups were also at a very high risk of fatal ketoacidosis, had slower growth, and had changes in brain structure.
When followed for 30 days preconception, a keto diet has also been shown to affect embryo growth and alter organ development. It can even impact brain development and has been suggested to increase anxiety and depression behaviours in adult offspring of mothers who were ketogenic in pregnancy.
If you have PCOS with insulin resistance (whether obese or not), controlling insulin regulation and sensitivity is still an important goal. This can be achieved by following a lower-carbohydrate diet and/or focusing on high-fibre, whole-grain carbohydrates (like avocados and vegetables) instead of processed sugars and simple carbohydrates.
Along with this, if you’re struggling with obesity, healthy and controlled weight loss can further support your fertility. Regular physical activity can also help burn off excess adipose tissue and stabilize insulin levels.
The bottom line: If you decide to try a keto diet, it would be safest to follow it before the preconception period, meaning you should be out of ketosis three months before you’re going to try to conceive.