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Do You Really Need to Lower Your BMI for IVF to be Successful?

Many IVF clinics recommend women with a BMI of over 35 kg/m2 lose 10% (or more) of their body weight to get into a healthy BMI range for IVF prior to starting treatment. And while it may be coming from good intentioned healthcare providers, I have a hard time swallowing this as the best recommendation for mommas who are looking to conceive.

But, what does the research say? Is losing weight to get a lower BMI for IVF really all that helpful? Let’s take a look at what research studies have found.

The BMI and IVF Link – What’s the Evidence?

If you hop onto PubMed or Google Scholar, you’re going to see a myriad of articles that show a connection between BMI and IVF outcomes. Hence, the recommendation that many IVF clinics make – ‘you wanna do IVF, you’re gonna need to drop some weight’. (eek, even writing that makes me cringe).

Many IVF clinics report that IVF is more successful after weight loss for several reasons. In 2015, The American Society for Reproductive Medicine published a report that said obesity impacts fertility by reducing egg quality, endometrial function and inhibiting ovulation.

I’m just going to leave those three reasons right there for a second… we’ll get back to those in a second.

But, if you dig a bit deeper there is also conflicting data that shows only minimal differences in success rates between obese women who lower their BMI for IVF and those who do not. In fact, at least two randomly controlled trials (aka: well-designed studies) did not show a significant difference between women who first lost weight for IVF and those who did not.

And if these two well designed studies tell us anything, it’s this: BMI isn’t an end all be all for IVF success.

Let’s Shift the Focus from BMI for IVF to Well Nourished for IVF.

Frankly, it worries me that so many IVF clinics continue to make the recommendation to lose weight for IVF. Because, first off (and like I said before)… the evidence isn’t a slam dunk in favor of needing to lose weight for improved IVF outcomes.

Secondly, it wastes time. Especially in the women who are in their mid to late 30s. I mean, there is (unfortunately) a biological clock that does tick away and lessens the chance of conception in each passing year. So, is it really fair that these women are asked to drop pounds in exchange for a ticking clock?

And third, and maybe more than anything… it sets the momma up for failure.

Because you know what kind of research is a slam dunk? The research showing that calorie restricted diets don’t work to lose and sustain weight loss. End of story. Close the book. They don’t work.

Literally 80% of people who lose weight will regain that weight back PLUS more in the following 5 years.

Then, this coupled with the also well-known fact that reproduction and fertility take a pretty heavy hitting dose of nutrients to keep the whole system up and running. Well, you can see where I am going.

Fertility is a nutrient expensive process. I mean, you are LITERALLY growing another human being.

Cutting calories to less than 1500 per day makes it darn near impossible to get in all the important nutrients you need to fuel your body. And even more… fuel your reproductive system.

So, let’s talk nutrients for IVF instead of BMI for IVF.

I’m going to bring back up those three things I talked about above. Ya, know, the three things the The American Society for Reproductive Medicine published in 2015 as reasons to encourage losing weight for IVF.

But, instead of talking about how weight impacts these three things, let’s talk about how good and foundational nutrition can HUGELY impact these aspects of fertility.

#1: Egg Quality

Eggs undergo a lot of growth and development in the 90-100 days leading up to ovulation. During this time, the DNA in eggs replicate many times and it takes a lot of nutrients to accurately replicate DNA. Nutrient deficiencies, even if subclinical (aka: not picked up on standard nutrient testing) can hugely impact how successful an egg can replicate DNA.

While obesity may impact egg quality, so does undereating and a diet that doesn’t hit key nutrients.

And just to name a few nutrients involved in DNA replication and synthesis: healthy fats, vitamin A, vitamin E, zinc, folate, and antioxidants.

#2 Endometrial Function

The endometrium is the lush lining of the uterus. A fertilized egg implants into the endometrium and nourishes and protects the developing embryo. A healthy endometrium is vital for achieving pregnancy and sustaining pregnancy.

And, as you guessed – great nutrition can help build a healthy endometrium. Iron, vitamin E, and omega-3 fatty acids are all important to build a healthy endometrium.

Similar to egg quality, a diet that is limited in calories will likely also have limited intake of these key nutrients for endometrium health.

#3 Regular Ovulation

This is a big one. Many people blame anovulatory cycles on weight and tell women that losing weight will help them to ovulate regularly. But, weight isn’t the root cause here.

In most cases, the root cause is actually poorly regulated blood sugars and insulin resistance. And eating a balanced diet with correct carbohydrate, fat, and protein distribution will help to overcome the insulin resistance and allow for regular ovulation.

The answer here isn’t calories; it is learning how to nourish your body with well rounded meals that keep your blood sugar stable.

The Bottom Line:

When all is said and done, I just can’t get behind asking women to lose weight quickly for IVF. Sure, weight loss may naturally happen when you start to make meaningful changes to your diet (aka: nourishing your body and fertility well). But, that’s secondary. The focus is on feeding your fertility, not dropping pounds.

Just remember, these two statements don’t jive:

-Lose weight by seriously cutting calories to help your fertility.

-Eat a ton of important nutrients to fuel your reproductive tract and your fertility.

And as a dietitian, I align WAY more with the second statement. I find that focusing on weight is a losing battle. And for many women, a battle that feels very much out of their control.

But, making real changes to their diets; changes that they know will support their egg quality, endometrium health, and encourage regular ovulation. Well, these things feel a lot more within their control and the results can be HUGE.

If you are ready to learn more about how to nourish your fertility, without worrying about the scale or dropping X amount of pounds, check out the Fertile Diet Reboot.


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