Fat and Fertility: Should You Follow a High or Low Fat Diet for Fertility?

Thankfully, gone are the days where we’re told to avoid dietary fat at all costs. We know that fat is important for our health in many ways. But what about when it comes to fat and fertility? Should you follow a high or low-fat diet for fertility?

Fat and Fertility: The Basics

Fats are the building blocks for our sex hormones and so it makes sense that they play a very important role in reproductive health. 

Plus, we know that both eggs and very early embryos rely on fat as a source of energy.

So it makes sense that too little and too much dietary fat has been associated with changes to the menstrual cycle and difficulty conceiving.

Let’s Look at the Effects of Having Too Little Fat and Fertility

In general, any diet with inadequate energy (calories), can lead to infrequent cycles, anovulatory cycles, amenorrhea (where periods stop completely) or luteal phase defects. 

This is likely to be particularly important if you carry less body fat or weight (including having a low BMI). If you think about it, it really does make sense, if the body feels like food is scarce, it’s obviously not going to be a good time to reproduce — pregnancy takes a lot of energy! 

As well as leading to these changes, a low-fat diet has been linked with longer follicular phase. While this doesn’t exactly mean you are less likely to fall pregnant, it does means you’ll get fewer chances in a year to try! And it’s a clear sign that your cycles are being affected by the lack of fat in your diet and that you need to increase your intake. 

So How About a High Fat Diet and Fertility?

A diet with excess fat can harm your fertility in three main ways: 

1. Insulin Resistance 

Although we usually think about our blood sugar levels as being related to our carbohydrate intake, fat and protein also play a crucial role. A diet very high in fat, particularly saturated fat, has been shown to increase insulin resistance –especially if it also leads to excess weight gain. Insulin resistance is known to reduce ovulation, negatively affect egg quality as well as pregnancy and live birth rates.

Side note: On the other hand, including some fat in your meals, along with both protein and carbs, will help make sure your blood sugars rises gradually. This can help decrease insulin resistance in the long term. And the type of fat you’re consuming matters, a big review of over 100 studies found that having enough polyunsaturated fat, especially omega-3, consistently decreased insulin resistance. 

2. Dyslipidemia 

A high fat diet (again, particularly saturated fat) is linked with dyslipidemia, that is, abnormal amounts of the different fat types in the blood. A big study has shown this to increase time to pregnancy. Interestingly, the longest time to pregnancy was seen when both members of a couple had abnormal fat levels.  

3. Gut health

Studies have shown a high-fat diet can have a negative impact on the gut microbiota. 

Lots of research on the gut has come out in recent years and we now know that a healthy gut microbiome influences everything from immunity to mood. In terms of fertility, our gut health affects our hormone levels as well as inflammation, which is known to affect egg health. 

It’s likely the effect of a high-fat diet on gut health are at least in part caused by a lack of fibre, as most high-fat diets have reduced carbohydrates and fibre. A low fibre diet has lots of impacts on health, including increasing both 1. Insulin resistance and 2. Dyslipidemia! 

Lastly, having a healthy gut microbiome may help support your vaginal microbiome and emerging evidence is showing the health of your vaginal microbiome plays a role in fertility too!  

It’s important to note that we’re talking very high-fat diets here (looking at you keto!) We definitely don’t want you avoiding fat, as discussed above. And don’t worry, there is some good news coming for your post-transfer fries here!

 

Obviously, the relationship between dietary fat and fertility is a complex one. It’s important to make sure you’re not having too little or too much fat to support your fertility. But the types of fat matter too. Some fats seem to boost your fertility and others decrease it.