Understanding How Weight Affects Fertility

How Weight Can Affect Fertility

If you are trying to get pregnant, and are struggling to conceive, you are not alone. According to the U.S. Department of Health and Human Services, out of 100 couples, 12 to 13 of them will have difficulty getting pregnant or staying pregnant. Infertility can have many causes, and if you have been trying to conceive for at least a year and still haven’t gotten pregnant, you may want to speak to your doctor to see if there might be any medical causes for your infertility. Among the many possible causes for infertility, did you know that your weight could have an impact on your fertility?

Several studies have found a link between weight and fertility. Women who are overweight or underweight can experience difficulties conceiving and can also experience problems with their pregnancies. But, women alone aren’t affected. Overweight men can also experience fertility issues. Let’s explore.

Understanding BMI: Clinical Assessments of Weight?

To better understand the role that weight plays in fertility, we need to first understand how clinicians evaluate weight and obesity. According to the Centers for Disease Control and Prevention, 42.2% of adults are considered obese in the U.S. What does it mean to be obese or overweight? Doctors use a measure known as BMI (body mass index). While using BMI to measure health has its limits (it doesn’t take into account things like physical activity, overall health, or other issues), it is a number used by researchers to determine the impact that weight can have on pregnancy and other medical issues. BMI offers reliable numbers by which researchers and doctors can group different women by their weights and measure their pregnancy outcomes and pregnancy risk rates.

This is the formula you can use to calculate your BMI, provided by the CDC:

[weight / (height in inches)2] x 703 

Confusing? You can also use the CDC’s Adult BMI calculator found here to learn your BMI.

When calculating your BMI, you’ll get a number.

But, what does this number mean? A BMI under 18.5 is considered underweight, while a BMI between 25 and 29.9 is considered overweight. Those with a BMI over 30 are considered obese. Being overweight and underweight can impact various aspects of your health, your fertility being among them. Let’s explore how.

Fat Can Interfere with Fertility

Having too much, or too little fat, can impact a woman’s estrogen levels. Let’s look more closely into the science underlying why this happens—for both overweight and underweight women.

According to research published in the journal of Reproductive Biology and Endocrinology, adipose tissue, or fat, can essentially act like “an endocrine organ.” Put simply, fat tissue can release hormones as if it were a hormone-producing organ, leading to too much of certain hormones, which can interfere with fertility. The endocrine system is responsible for releasing hormones, which in turn regulate biological processes, including fertility and pregnancy. Hormones, like estrogen and testosterone regulate human fertility. Fat tissue can cause a woman to have too much estrogen. Basically, fat can act like an endocrine disruptor. According to the Daily Wellness, endocrine disruptors “are chemicals that can block your body’s natural hormones or mimic them.” Fat, in excess, can sometimes act just like a dangerous chemical in food or water.

In excess, fat can lead the body to produce too much estrogen. Research published in the Journal of the American Academy of Dermatology found that fat tissue can convert a hormone known as androgen into estrogen. This can lead to excess estrogen in overweight or obese women. Too much estrogen can lead to irregular periods, spotting, and ovulation problems. Fat can also interact with various body systems, including oocyte differentiation and maturation. In other words, fat can interfere with the maturation of egg cells. Fat tissue can impact the “hypothalamus-pituitary-gonadal axis,” which is the system that regulates the ovaries, embryo implantation, and pregnancy.

Without mature egg cells (through ovulation), a woman cannot conceive. But even if an egg is released and fertilized, a woman can still have trouble getting pregnant if the embryo doesn’t implant. Embryo implantation is the stage where the embryo attaches to the wall of the uterus, an essential stage for pregnancy to occur. If any of these processes are disrupted by fat or by hormonal imbalances due to fat, a woman can have trouble getting pregnant.

The journal of Women’s Health also notes that obesity has been linked to polycystic ovarian syndrome. This condition is associated with a range of health issues, one of them being the inability of the ovaries to release eggs. Women who are heavier are at greater risk of suffering from insulin resistance, which can leave them with high blood sugar levels, which can lead to a range of pregnancy complications and fertility issues.

Being underweight can also impact a woman’s production of estrogen. According to the U.S. Department of Health and Human Services, women who are underweight can stop producing estrogen, which can interfere with ovulation. If a woman isn’t ovulating, the egg cannot get fertilized, so pregnancy can’t happen.

The key takeaway for female fertility is this: the body needs enough fat to support a developing fetus, but not so much fat that the tissue impacts a woman’s health and other body systems. Fat can regulate estrogen levels in your body, which in turn can impact your ability to get pregnant.

Weight and Male Infertility

Women often get blamed for fertility issues when a couple struggles to conceive, but male obesity and weight can also impact a couple’s fertility. The Centers for Disease Control reports that in 35% of couples suffering from infertility, the male role must be considered, and in 8% of couples suffering from infertility male infertility is the primary cause. According to Penn Medicine, male obesity can increase body temperatures around the scrotum. Warmer testicles have been linked to lower sperm quality. According to the journal, Spermatogenesis, studies have shown that there is a link between obesity and lower sperm concentration and reduced sperm motility. However, it is unclear whether these findings could be linked to obesity alone, or to other lifestyle factors. What the research does show, however, is that obese men are more likely to produce sperm with DNA damage, which can not only have negative implications for fertility, but can also impact the embryo and fetus. Men with higher BMIs were also found to have higher levels of estrogen and lower levels of testosterone, hormones which can impact male fertility. Just as adipose tissue (fat tissue) can increase the production of estrogen in women, fat tissue can have the same impact on men. 

So, a woman’s weight is not the only factor in fertility, but the man’s weight can also play a role.

Weight and Pregnancy

Weight can also impact pregnancy. According to the journal of Reproductive Biology and Endocrinology, the miscarriage rate in obese women was as high as 40%. Even when women don’t miscarry, being overweight can have negative implications for the developing fetus. The journal of Obstetrics and Gynecology reports that overweight and obese women were more likely to suffer complications during their pregnancies. Overweight women were more at risk of suffering from gestational diabetes, preeclampsia, and were more at risk of delivering overweight babies. Gestational diabetes is a kind of diabetes developed by pregnant women. Babies born to women with gestational diabetes are at risk of having health issues. Preeclampsia is a dangerous condition in which a pregnant woman develops high blood pressure. This condition can pose a risk to the mother and the fetus and women with this condition can suffer from strokes, seizures, or premature labor. If you are overweight and are planning to become pregnant, losing the weight can not only improve your health, but can protect the health of your baby.

Weight and Fertility Treatments

Your weight can also impact your chances of success with fertility treatments, like I.V.F. and I.U.I. According to the Journal of Reproductive Sciences, obese women may not respond well to medications used to induce ovulation, and they may need more of these medications to successfully conceive. Women may produce fewer viable eggs, have poorer fertilization rates, and lower-quality embryos when they are overweight or obese. Obese women are also more likely to have a miscarriage. Fatty acids can also have a toxic effect on reproductive tissues, leading to cell damage and inflammation, resulting in problems of ovarian follicle development, problems with egg maturation, and abnormal embryo implantation due to disrupted cellular processes. The Journal of Reproductive Sciences also notes that obese women can improve their chances of success if they lose anywhere between 5-10% of their weight.

Next Steps to Take if You Think Weight May Impact Your Fertility

If you think your weight might be impacting your fertility, you may want to speak to your doctor about losing weight and speak to your doctor about what an ideal weight might be for you. Your doctor can review your eating habits, medications, and wellness supplements to see what plan might be best for you going forward. The Centers for Disease Control reports that weight loss programs that involve lifestyle changes that result in a gradual, rather than rapid, loss of weight often result in longer-lasting weight loss. What are some general tips?

• Take stock of your current lifestyle in consultation with your physician. What aspects of your lifestyle might be leading to weight gain? What aspects of your lifestyle might be preventing weight loss? A balance of healthy eating and regular physical activity is required to lose weight. Identifying foods and lifestyle factors that might be contributing to your weight is an important first step.
• Set healthy eating goals. According to the National Heart, Lung, and Blood Institute, in order to lose about one pound a week, individuals will need to reduce their daily calorie intake by anywhere between 500 and 750 calories. Diets should emphasize fruits, vegetables, whole grains, and fat-free dairy, as well as lean meats, and limited sugar, as well as limited saturated and trans fats. 
• Set realistic, specific, and measurable goals with regards to diet and exercise. For example, “I will go to the gym three times a week, to do 45 minutes of jogging on the treadmill,” is much more specific than making a vague goal to do more weekly cardio.  
• Follow through on your goals, but be forgiving. Remember that change takes time. Forgive yourself if you experience setbacks. If you are struggling to keep to a plan, consider modifying the plan so that it is more realistic. For example, if you can’t make it to the gym a few times a week, try starting out with the goal to go once a week, and build from there. If you can’t meet your target diet at first, start smaller. Change one meal a day instead of all three, and build from there. 

A balance of proper diet and exercise can make a big difference not only for your health, but also for the health of your future baby.

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