Recent advances in understanding the relationship between long- and short-term weight change and fertility [version 1; referees: 2 approved]

The impact of excess body weight on fertility is well recognized among both women attempting to conceive spontaneously and those attempting to conceive with medical assistance. Although many leading societies of reproductive medicine have proposed weight loss as a means to counteract the negative consequences of obesity on fertility, there is limited research on this topic. In this review, we provide a brief overview of the recent advances in the literature focused on how long- and short-term weight change affects fertility among women. Overall, despite initial hope that weight loss may be beneficial for fertility, two large well-conducted randomized controlled trials have consistently shown that short-term weight loss among overweight and obese women undergoing infertility treatment does not improve a woman’s probability of live birth. The observational evidence among women attempting to conceive without medical assistance also suggests limited benefits of weight loss on fecundity or pregnancy loss. In contrast, substantial weight gain between consecutive pregnancies, in the year prior to pregnancy attempt, and throughout adulthood appears to be harmful for not only time to pregnancy but also pregnancy maintenance. Future research focused on efforts to prevent weight gain during adulthood is needed to better understand whether these types of interventions may have beneficial effects on fertility

Adherence to the Mediterranean diet and body fat distribution in reproductive aged women

Background/Objectives Adherence to the Mediterranean Diet (MD) high in fruits, vegetables and monounsaturated fats, has been associated with lower body mass index. Associations with measured body fat, including regional adiposity, have not been previously investigated. We examined the associations between the alternate Mediterranean Diet Score (aMED), anthropometry and measured adiposity by dual energy x-ray absorptiometry. Subjects/Methods This study included 248 healthy females, aged 18–44 years from the BioCycle Study. Each woman’s aMED (range 0–9) was calculated from up to eight 24-hr dietary recalls over 1–2 menstrual cycles (>97% had ≥7 recalls). Multiple linear regression was used to determine whether aMED and its specific components were associated with total and regional adiposity after adjusting for age, race, education, physical activity and energy intake. Results: Participants had an average (SD) aMED of 4.2 (1.7) and percent body fat of 29.5 (6.0)%. Significant inverse associations were found between aMED and all the examined adiposity measures except waist to hip ratio. Among the DXA measures, a 1-unit increment in aMED was associated with a 0.06 (95% CI:−0.09,−0.02) lower trunk-to-leg fat ratio (T/L), a measure of upper to lower body fat. In an analysis examining T/L as an outcome with the separate components of the aMED, T/L was lower with increased legume consumption (β=−0.280, 95% CI:−0.550,−0.010) but was higher with increased consumption of red and processed meat (β=0.060, 95% CI:0.002,0.117). Conclusions: Adherence to the aMED was associated with lower total and regional adiposity, adding to the mounting evidence of the health benefits of the MD

The Impact of Dietary Folate Intake on Reproductive Function in Premenopausal Women: A Prospective Cohort Study

Background: Folic acid is recommended to reproductive-aged women to prevent birth defects, though little is known about the effects of dietary intake on other reproductive outcomes. Improved pregnancy rates have been documented after folic acid supplement use, suggesting a possible link with ovulation, however research is limited. Our objective was to evaluate the association between dietary folate intake, hormone levels, and sporadic anovulation in healthy, regularly menstruating women. Methodology/Principal Findings: The BioCycle study (2005–2007) prospectively followed 259 healthy women aged 18–44 years from the western New York region for up to 2 menstrual cycles. Total folate and specific sources of folate were assessed up to 4 times per cycle by 24-hour recall. Estradiol, progesterone, luteinizing hormone, and follicle-stimulating hormone were measured in serum up to 8 times per cycle, timed using fertility monitors. Anovulation was defined as a cycle with peak progesterone concentration ≤5 ng/mL and no LH peak in the mid/late luteal phase. Higher intake of dietary folate (in dietary equivalents) across tertiles had a marginally significant association with greater luteal progesterone levels (P trend 0.08). Higher intake of synthetic folate was significantly associated with higher luteal progesterone levels (P trend 0.05). Specifically, women in the 3rd tertile of synthetic folate intake had, on average, 16.0% (95% CI, 0.5–33.8%) higher luteal progesterone levels compared to women in the 1st tertile. Moreover, consumption of synthetic folate was significantly and inversely associated with anovulation such that women in the 3rd tertile had a 64% (95% CI, 8–86%) decreased odds of anovulation compared to the women in the 1st tertile (P trend 0.03). Conclusions/Significance: These findings suggest that a diet high in synthetic folate may be associated with increased progesterone levels and lower risk of sporadic anovulation. Further study of the effect of dietary folate and folic acid supplement use on reproductive health is warranted

Effect of Dietary Fiber Intake on Lipoprotein Cholesterol Levels Independent of Estradiol in Healthy Premenopausal Women

High-fiber diets are associated with improved lipid profiles. However, pre- and postmenopausal women respond differently to fiber intake, suggesting that endogenous estradiol mediates the effect. The authors' objective was to determine the direct effect of fiber intake on lipoprotein cholesterol levels independent of estradiol among premenopausal women. The BioCycle Study, a prospective cohort study conducted at the State University of New York at Buffalo from 2005 to 2007, followed 259 healthy women for up to 2 complete menstrual cycles. Serum lipoprotein and hormone levels were measured at 16 visits timed using fertility monitors. Fiber intake was assessed by 8 24-hour recalls. Marginal structural models with inverse probability weights for both lipoprotein and estradiol levels were used to estimate controlled direct effects of the highest category of fiber intake (≥22 g/day vs. <22 g/day) while accounting for age, body mass index, total energy, vitamin E intake, physical activity, luteinizing hormone, follicle-stimulating hormone, and progesterone. Reductions were observed in total and low density lipoprotein cholesterol in women with higher fiber intakes. Direct effects were greater than total effects. These analyses suggested that estradiol mediates at least part of the association between fiber and cholesterol among premenopausal women. More research is needed to elucidate the biologic mechanisms driving these associations

Genome-wide analysis identifies genetic effects on reproductive success and ongoing natural selection at the FADS locus

: Identifying genetic determinants of reproductive success may highlight mechanisms underlying fertility and identify alleles under present-day selection. Using data in 785,604 individuals of European ancestry, we identified 43 genomic loci associated with either number of children ever born (NEB) or childlessness. These loci span diverse aspects of reproductive biology, including puberty timing, age at first birth, sex hormone regulation, endometriosis and age at menopause. Missense variants in ARHGAP27 were associated with higher NEB but shorter reproductive lifespan, suggesting a trade-off at this locus between reproductive ageing and intensity. Other genes implicated by coding variants include PIK3IP1, ZFP82 and LRP4, and our results suggest a new role for the melanocortin 1 receptor (MC1R) in reproductive biology. As NEB is one component of evolutionary fitness, our identified associations indicate loci under present-day natural selection. Integration with data from historical selection scans highlighted an allele in the FADS1/2 gene locus that has been under selection for thousands of years and remains so today. Collectively, our findings demonstrate that a broad range of biological mechanisms contribute to reproductive success

Genome-wide analysis identifies 12 loci influencing human reproductive behavior.

The genetic architecture of human reproductive behavior-age at first birth (AFB) and number of children ever born (NEB)-has a strong relationship with fitness, human development, infertility and risk of neuropsychiatric disorders. However, very few genetic loci have been identified, and the underlying mechanisms of AFB and NEB are poorly understood. We report a large genome-wide association study of both sexes including 251,151 individuals for AFB and 343,072 individuals for NEB. We identified 12 independent loci that are significantly associated with AFB and/or NEB in a SNP-based genome-wide association study and 4 additional loci associated in a gene-based effort. These loci harbor genes that are likely to have a role, either directly or by affecting non-local gene expression, in human reproduction and infertility, thereby increasing understanding of these complex traits

Reply to AT Wijayabahu

This work was supported by Public Health Service grant R01 CA158313 from the National Cancer Institute, NIH, US Department of Health and Human Services (to KBM), and by the World Cancer Research Fund (2010/245)