By marie Dufour, RD – Researchers found that it took an average of five days for oral contraceptive drugs to achieve their maximum concentration in women of normal weight, but that it took an average of 10 days for obese women. This doubles the window of opportunity for fertilization. This doubles the risk of failure of oral contraception.
The efficacy of oral contraceptives, like that of many other drugs, is studied on the basis of normal-weight people. With the recent prevalence of overweight and obesity, and with an increasing number of women weighing in excess of 130% of their desired body weight, the recommended doses may not reach the efficacy originally predicted.
Would increasing the dose make a difference in blood levels of oral contraceptives? It is yet unclear. But what is clear is that increasing the dose would definitely raise the risk of deep venous thrombosis (DVT), stroke, and heart attacks. Caught between safety and efficacy, the many physicians who currently tend to decrease the dose of oral contraceptives in obese women to avoid DVT, are now faced with the need for dose increase to boost efficacy.
What to do then? This is one more evidence that obesity and overweight are dangerous to not only our general health, but also to our reproductive health. If we don’t want to walk around pushing a baby stroller, it’s time to walk, run, bike, swim, and do anything we can to stay out of the obesity zone.
Ref: Alison B. Edelman et al, Impact of obesity on oral contraceptive pharmacokinetics and hypothalamic–pituitary–ovarian activity doi:10.1016/j.contraception.2009.04.011
Filed under: Lifestyle , contraception, healthy lifestyle, healthy living, Marie Dufour RD, nutrition, obesity, oral contraceptive, pregnancy, public health, weight loss, women's Health