Obesity and overweight are two medical problems that are increasingly present at reproductive ages. In addition, both affect other pathologies, increasing the risk of suffering from others or worsening existing ones. The most common are diabetes and heart disease, although there are more and more problems related to obesity, such as some types of tumors.
In recent years, there has been an increasing incidence of overweight related to infertility. Incidence that has caused increasing research on how body mass index and related lifestyle affect fertility in both men and women.
Overweight in women is defined as a body mass index (BMI) of 25 kg/m2 or higher, and obesity is defined as a BMI of 30 or higher.
Several studies have shown that obese women have a higher risk of non-fertility and infertility and require higher doses of gonadotropins and longer periods of ovarian stimulation during assisted reproduction treatments (4).
This means that obesity decreases the probability of pregnancy in terms of conception both naturally and in assisted reproduction treatments, according to the latest studies (5).
On the other hand, it is important to point out that to date it has not been demonstrated which specific factors are affected by obesity (oocyte quality, endometrial receptivity, among others) since the results of these factors are in conflict (3).
OBESITY AND FERTILITY
Eating a healthy diet and exercising regularly prevents complications during pregnancy, such as the possible onset of gestational diabetes, which usually appears around the 24th week of gestation.
Notably, this weight loss leads to a significant improvement in women’s testosterone and free androgen levels in women with polycystic ovary syndrome (6). The woman’s diet prior to pregnancy may also be beneficial in optimizing pregnancy outcomes and increasing live births with assisted reproductive treatments (6).
Even so, it can be said that there are few studies that have analyzed the impact of weight loss in obese women who wish to become pregnant. The results obtained have been insignificant, probably due to methodological deficiencies (5).
Although most researchers agree that body mass index has an influence on the success rate of assisted reproductive cycles. This is based on well-established clinical data, mostly from observational studies, suggesting that weight loss should always be a primary goal in obese patients before starting a fertility treatment or planning a pregnancy. In the case of a high BMI, there are a greater number of disadvantages, such as having to administer a greater amount of gonadotropins (6), lower endometrial receptivity (4), poorer embryo quality, or greater risk of miscarriage (6).
In some cases it has been observed that using donor oocytes improved the results, but the exact impact of obesity on IVF results is not known due to the lack of standardized criteria, heterogeneity of the studies and the retrospective nature of most studies.
This article is based on specific studies on the subject in question.
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(3) Atzmon Y, Shoshan-Karchovsky E, Michaeli M, Aslih N, Shrem G, Ellenbogen A, et al. Obesity results with smaller oocyte in vitro fertilization/intracytoplasmic sperm injection cycles-a prospective study. J.Assist.Reprod.Genet. 2017; 34(9):1145-1151.
(4) Bellver J, Pellicer A, García-Velasco JA, Ballesteros A, Remohí J, Meseguer M. Obesity reduces uterine receptivity: Clinical experience from 9,587 first cycles of ovum donation with normal weight donors. Fertil.Steril. 2013; 100(4):1058.
(5) Espinos JJ, Polo A, Sanchez-Hernandez J, Bordas R, Pares P, Martinez O, et al. Weight decrease improves live birth rates in obese women undergoing IVF: a pilot study. Reproductive Biomedicine Online 2017; 35(4):417-424.
(6) Lim SS, Noakes M, Norman RJ. Dietary effects on fertility treatment and pregnancy outcomes. Curr.Opin.Endocrinol.Diabetes Obes. 2007; 14(6):465-469. (16) MacKenna A, Schwarze JE, Crosby JA, Zegers-Hochschild F. Outcome of assisted reproductive technology in overweight and obese women. J.Bras.Reproducao Assistida 2017; 21(2):79-83.
