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Body fat plays an important role in fertility and being overweight or underweight can affect the hormonal balance needed for normal menstrual cycles and regular ovulation. The American Society of Reproductive Medicine (ASRM) estimates that 6% of primary infertility is caused by being overweight and another 6% by being underweight based on epidemiological data. The good news is that this type of infertility can usually be corrected by getting the body weight back into the normal range.

In order to determine if you are overweight or underweight you must calculate your BMI. BMI stands for body mass index, a numerical value of your weight in relation to your height. BMI is a good indicator of healthy weights for adults no matter what size their body frame is.

The Quetelet index (kg/m2) is the accepted method to calculate your BMI. To calculate your own BMI using the Quetelet index follow these three steps:

• Divide your weight in pounds by 2.2. This converts your weight into kilograms (kg)
  
• Multiply your height in inches by 0.0254 and then multiply that number by itself to calculate your height in meters (m2)
  
• Divide the kg by the m2 to determine your BMI

If math is not your favorite subject you can also go to: http://www.obesityinamerica.org/bmi_calculator.html
At this website you can enter your height and weight to quickly calculate your BMI. Once you have calculated your BMI see where you fall on the chart of BMI Categories:

• Below 18.5 = Underweight
  
• 18.5 - 24.9 = Healthy
  
• 25.0 - 29.9 = Overweight
  
• 30.0 - 39.9 = Obese
  
• Over 40 = Morbidly Obese
  

The Impact of Obesity on Fertility and Pregnancy
According to the Centers for Disease Control (CDC) recent increases in the number of overweight and obese Americans are seen across all ages, races, ethnic groups, and education levels in the United States. It is common knowledge that those who are overweight or obese have a higher incidence of sleep and breathing problems, high blood pressure, high cholesterol and Type 2 diabetes, among other conditions. What may be less obvious is how weight can affect fertility and complicate pregnancy.

Reproductive problems associated with obesity are for the most part related to ovulation problems. Infrequent ovulation leads to irregular or infrequent menstrual cycles and infertility. Obesity can also be a symptom of polycystic ovarian syndrome (PCOS) (See April Current Trends for Updates in PCOS). This is a medical condition characterized by irregular menstrual cycles, anovulation (no ovulation) and elevated levels of male hormones or androgens. Finally, obesity increases risk during surgery and decreases the success of fertility treatments.

If you are pregnant and obese there are risks to both mother and baby. Pregnant women are at increased risk of high blood pressure, pregnancy-related diabetes, miscarriage and Cesarean section, while babies may be at increased risk for birth defects and high birth-weight. A recently published study of egg donor recipients suggests that obesity may have detrimental effects on the lining of the uterus (endometrium) that result in lower pregnancy rates.

Obesity can affect men's fertility as well. A 2005 study with 520 men found that as body mass index (BMI) increased, sperm count and semen quality decreased.

The Impact of Being Underweight on Fertility and Pregnancy
Like trends in obesity the incidence of eating disorders has also increased over the last three decades but these disorders occur mainly in adolescent girls and tend to peak in women during their childbearing years. Eating disorders include anorexia nervosa, a condition that involves obsessive dieting and starvation; and bulimia, a condition that involves binge eating followed by the use of laxatives or inducing vomiting to purge the excess calories.

The degree to which weight loss affects fertility is variable and to make matters worse, the condition is often not reported to a health care professional. One of the first signs of severe weight loss is amenorrhea (absent menstrual cycle), the body’s defense when a woman is not taking in enough calories to sustain herself, let alone a baby. Even in mild cases when a woman does ovulate and menstruate, the hormone production from the ovaries may not be high enough to develop the lining of the uterus enough for the embryo to implant.

According to the American Pregnancy Association eating disorders can also have a negative effect on pregnancy. The risks of miscarriage, premature labor, low birth weight infants, stillbirth, delayed fetal growth, respiratory problems, and pregnancy-related diabetes are increased. They also report that women with eating disorders have higher rates of post-partum depression and difficulties with breastfeeding.

Weight Management
If you are obese, a weight loss of even 5% to 10% can improve ovulation and pregnancy rates as well as conditions such as high blood pressure and diabetes. Getting your BMI in the healthy range is a balance of exercise and caloric intake but it requires a serious commitment. The American College of Obstetricians and Gynecologists (ACOG) does not recommend trying to lose weight while you are pregnant but suggests the following:

Your pre-pregnancy BMI.............Your suggested weight gain
Less than 19.............................................35 lbs
19-24.9....................................................25-35 lbs
25-29.9....................................................15-25 lbs
30 or greater.............................................15 lbs

If you are underweight, experts suggest you get counseling to address the underlying cause of the eating disorder before you try to get pregnant. Schedule a pre-conception appointment with your health care provider to discuss overall health and medications such as folic acid and prenatal vitamins. Finally, meet with a nutritionist to develop a dietary plan that allows you to achieve and maintain a healthy weight.

Fertility Source is a new podcast series offered by FertilityJourney.com. Each episode will explore a different topic related to fertility with featured guest experts to provide insight and guidance. You can access the podcast on how body weight and metabolism can have an impact on both women's and men's fertility by visiting the following website: http://www.fertilityjourney.com/support/podcasts/index.asp?svarqvp2=0

For additional information on this topic you can also visit these websites:

American College of Obstetricians and Gynecologists: www.acog.org/publications/patient_education/bp064.cfm

American Diabetes Association. www.diabetes.org/type-2-diabetes.jsp

American Dietetic Association: www.eatright.org

American Obesity Association. www.obesity.org

American Pregnancy Association: www.americanpregnancy.org

The Endocrine Society and The Hormone Foundation: www.obesityinamerica.org/trends.html

US Department of Agriculture: www.mypyramid.gov.

References:

ACOG Education Pamphlet: Weight Control: Eating Right and Keeping Fit. Available at: www.acog.org/publications/patient_education/bp064.cfm

ASRM Patient’s Fact Sheet Weight and Fertility. Available at: http://www.asrm.org/Patients/FactSheets/weightfertility.pdf

Bellver J et al. Obesity and poor reproductive outcome: the potential role of the endometrium. Fertil Steril 2007; 88: 446-51.

Eating disorders during pregnancy. The American Pregnancy Association. Available at: http://www.americanpregnancy.org/pregnancyhealth/eatingdisorders.html

Franko D et al. Pregnancy complications and neonatal outcomes in women with eating disorders. Am J Psychiatry 2002; 159: 1249-50.

Jequier, E. (1987). Energy, obesity, and body weight standards. Am J Clin Nutr, 45, 1035-1047

Kort HI, Massey JB, Elsner CW, Mitchell-Leef D, Shapiro DB, Witt MA, Roudebush WE. Impact of Body Mass Index Values on Sperm Quantity and Quality. J Androl. 2005 Dec 8;

Mitchell-Gieleghem A, Mittelstaedt M, Bulik C. Eating disorders and childbearing:concealment and consequences. Birth 2002; 29: 182-91.

Rich-Edwards, J.W., Spiegelman, D., Garland, M., et al. 2002. Physical activity, body mass index, and ovulatory disorder infertility. Epidemiology, 13,2,184-190.

Speroff, L., Glass, R.H., Kase, N.G. 1999. Clinical Gynecologic Endocrinology and Infertility (6th Edition). Baltimore: Lippincott, Williams and Wilkins.