Is a keto diet good for fertility?

Is a keto diet good for fertility?

You may know friends who are shunning carbohydrates in favour of a high fat ‘keto’ diet in the hope that this will increase fertility and wondered whether it’s just a fad or a worthwhile strategy? Here we look at some evidence and the pros and cons of ketogenic diets.

Are ketogenic diets a fad?

Far from being a new fad, ketogenic (aka ‘keto’) diets have been medically utilised for over 100 years with evidence it can help suppress seizures in children with epilepsy. However, the diet has seen a resurgence in the last decade as a weight-loss option and this new focus has also shone a light on whether it can be used for other medical conditions and whether it can help improve fertility.

How does keto work?

The keto diet aims to force your body into using fat rather than glucose as fuel - a process called ‘ketosis’. Instead of relying on sugars that come from carbohydrates (such as pasta, flour, grains, vegetables, and fruits), the keto diet relies on ketone bodies, a type of fuel that the liver produces from stored fat. While this can lead to weight loss, it is the metabolic changes that keto diets cause which interest doctors.

Why would ketosis impact fertility?

This has its origins in the theory that a cause of infertility in some overweight women is insulin resistance linked to their diagnosis of polycystic ovary syndrome. PCOS is the most common endocrine disorder in women of reproductive age. It is is a hormonal disorder causing enlarged ovaries with small cysts on the outer edges. Women with PCOS are sometimes found to have excess androgen hormones and too much insulin. PCOS is also known to be a metabolic disorder. In fact, there have been some doctors, researchers, and women’s health care advocates who have proposed that PCOS be renamed to “Metabolic Reproductive Syndrome” to give a more complete picture of what this syndrome involves. Because PCOS involves insulin and metabolism, it is one reason why the keto diet can be helpful in treating PCOS since it can help lower insulin levels and regulate blood sugar.

A 2019 study sought to investigate the effects of a ketogenic diet on women with a diagnosis of PCOS. While the study was relatively small - just fourteen women over a 12 week period - there were some promising results. The women all followed a ketogenic Mediterranean diet with phytoextracts (plant extracts) for 12 weeks. The results revealed a significant reduction of body weight (an average loss of 9.43 kg), BMI (down 3.35 points), and body fat (down 8.29 kg).

A significant decrease in glucose and insulin blood levels were observed, as well as a significant decrease of triglycerides, total cholesterol, and LDL (i.e. ‘bad’) cholesterol along with a rise in (‘good’) HDL levels. The LH/FSH ratio, LH total, and free testosterone -all of which have a negative effect on fertility- and DHEAS blood levels were also significantly reduced. Oestradiol, a string oestrogen, and progesterone, which are both a requirement for pregnancy also increased.

So for women whose fertility is compromised by PCOS, a medically supervised keto diet may be of benefit - but what if you haven't been diagnosed with PCOS? Well, there isn't as yet scientific any evidence that it has an impact, there is some anecdotal evidence that it helps, (however much depends of course on how healthy your diet was before).

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What can you eat on a keto diet?

A true medical ketogenic diet is strict and is not that easy to follow as it requires that you eat a lot of fats and deprive yourself of carbohydrates. In general, you are allowed fewer than 50 grams of carbs per day (and keep in mind that a medium-sized banana has about 27 grams of carbs!).

In a typical daily 2,000-calorie diet, the mix would be around 165-180 grams of fat, only 40 grams of carbs, and 75 grams of protein. Because the keto diet has such a high fat requirement, you’ll need to eat fat at every meal and much more than you would think as ‘normal’ for a medical diet. Healthy unsaturated fats are encouraged on the keto diet —like avocados, nuts (almonds, walnuts), seeds, tofu, and olive oil. But saturated fats from palm and coconut oils, lard, butter, and cocoa butter can also be included though of course, these are not healthy in high amounts.

Protein is a very important macronutrient as it can improve feelings of fullness and increase fat burning better than other macronutrients. However, keto dieters who eat a lot of lean animal foods can end up eating too much of it. When you eat more protein than your body needs, some of its amino acids will be turned into glucose via a process called gluconeogenesis which defeats the object of a keto diet as it prevents your body from going into full-blown ketosis.

The biggest challenge with following a keto diet is cutting down on carbs. While it may seem easy to avoid rice and pasta, in fact, all fruits and vegetables are rich in carbs and you’ll probably have to reduce your consumption in favour of fats. You can have certain fruits (such as berries) in small portions. Vegetables are generally restricted to leafy greens (such as kale, Swiss chard and spinach), cauliflower, broccoli, Brussels sprouts, asparagus, capsicums, onions, garlic, mushrooms, cucumber, and celery.

Are there risks?

While the benefits are as yet unproven, it should also be noted that a keto diet comes with risks:

  • Fats - it can be high in saturated fat which is linked to heart disease, and it can be hard to stick only to healthy fats like monounsaturated and omega-3 fats instead.
  • Nutrient deficiency - if you're not eating a wide variety of vegetables, fruits, and grains, you may be at risk for deficiencies in micronutrients, including selenium, magnesium, phosphorus, and vitamins B and C, so supplementation may be required.
  • Kidney problems - the kidneys help metabolize protein, and a keto diet may overload them.
  • Constipation - the keto diet is low in fibrous foods like grains and legumes.

In summary

Those risks add up — so if you are considering a keto diet, do make sure that you talk to a registered dietitian before you start as there may be better options for your specific needs.

The Flinders Fertility preconception care clinic may also be worth considering as we will review your diet and other lifecycle factors to give you the best chance of getting pregnant. The appointments which are with a specialist fertility nurse, take around one hour, and where required involves other associated health providers such as dietitians, naturopaths, and hypnotherapists. 

Want to find out more?

If you have any further questions, you can arrange a nurse chat with one of our fertility nurses.

For more health and wellness information on how to increase your chances of conception, check out our fertility news page, or download our e-book below.

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Mavropoulos JC, Yancy WS, Hepburn J, Westman EC. The effects of a low-carbohydrate, ketogenic diet on the polycystic ovary syndrome: a pilot study. Nutr Metab (Lond). 2005;2:35. Published 2005 Dec 16. doi:10.1186/1743-7075-2-35
Photo by Joshua Coleman