Why pushing for weight loss before conception does more harm than good
One thing that both breaks my heart and cheers me up is when I’m in one of the online nutritionist/therapist groups I belong to and I see a plea for a recommendation from a gynecologist or fertility doctor who isn’t Tell fat women (I use fat as a neutral description, like short, tall or thin) that they need to lose weight before they can get pregnant.
The recommendation to lose weight to improve your chances of having a successful, healthy pregnancy is widespread, but without any rigorous evidence to back it up. So why do many experts, medical societies, public health programs, and treatment centers urge weight loss before beginning fertility treatments? The answer is a mix of weight bias and epidemiological research showing there is Association between “obesity” and infertility. But association is not the same as cause and effect.
“Healthcare providers know that obesity is associated with greater complications in pregnancy. Fertility providers are also aware of the link between obesity and lower fertility. The time to pregnancy can be twice as long as in women with an increased BMI [body mass index]said Angela Thyer, physician and founding partner of Seattle Reproductive Medicine. “Based on these historical studies, doctors hypothesized that if women could lose weight, they could improve their time to conception and fertility. They recommended weight loss without knowing if it really helped.”
A recent randomized controlled trial — the kind of study that can prove cause and effect — found that weight loss didn’t help. Results from the FIT-PLESE study, published in January in PLOS Medicine, found that 379 women with a BMI of 30 or more and unexplained infertility — unexplained because the women had normal ovulation — underwent a 16-week intensive weight-loss intervention A low-calorie diet, physical activity (increasing step count up to 10,000 per day), and medications that reduced fat intake were no better at improving fertility or birth outcomes than an intervention that simply increased physical activity. And that’s despite the fact that the women in the weight loss intervention lost about 7% of their starting weight. The authors concluded that there is no strong evidence to recommend weight loss before conception in women with a BMI in the “obese” range and unexplained infertility.
“It takes well-designed studies like this to change existing dogma,” Thyer said, adding that this study surprised many providers because it disproved long-held beliefs about weight loss and fertility. “Now we can say with confidence that there is no evidence that weight loss improves conception in women who are obese or overweight with ovulatory infertility.”
As surprising as the study may be, it has company. A 2016 randomized controlled trial published in the New England Journal of Medicine found that women with infertility — some who ovulate regularly and others who don’t — who underwent a similar low-calorie diet intervention had fewer healthy births than women who did not attempt weight loss.
“Reducing body fat can have a positive impact on reducing insulin resistance and inflammation, which can improve conception rates,” said registered dietitian Judy Simon, owner of Mind Body Nutrition. “But when a person chooses a severely restricted calorie diet, they are more likely to be missing out on key nutrients that optimize fertility and pregnancy. I am amazed that a woman can have an average or low BMI and be cleared for IVF [in vitro fertilization], yet she may have an eating disorder and be malnourished. In fact, women who present to a fertility clinic are more likely to have a past or current eating disorder. Weight does not equate to health, especially when diet and lifestyle choices are factored in.”
Thyer said that if weight loss could help a specific patient for a specific purpose, it must be approached with compassion and ideally with expert guidance. “When weight loss is recommended without direction, patients can leave medical treatment dejected and discouraged and disappear for years,” she said. “And we know that as women age, so does their fertility. Unfortunately, I have seen women in my practice where this has happened.”
For more than a decade, Simon and Thyer — who will be speaking at the Seattle Reproductive Symposium in May on Check Your Weight Bias at the Door: How to be a Body-Affirming Health Care Provider — have offered Food for Fertility classes with this focus about learning eating skills – including meal planning and cooking together – and lifestyle changes in a supportive group environment. “Many of our participants who were preparing for IVF actually got pregnant naturally after eating regularly and feeling more confident in their bodies,” Simon said. All without a focus on weight loss.
“We do not deny women fertility treatments based on BMI,” Thyer said. “We encourage all women to optimize their pre-conception lifestyle by eating a plant-based, wholesome and fertility-enhancing diet, exercising regularly every day, reducing use of substances such as alcohol, tobacco and cannabis, and aiming for restful, restful sleep, De-stressing and maintaining a loving and supportive network of friends and family throughout their journey to pregnancy.”
Some providers may still be recommending weight loss based on older information, Thyer said. “Fortunately, the tide is changing. Many providers are now aware that weight loss alone may not benefit fertility for most patients with a higher BMI. Many are also aware that restrictive dieting is not healthy, is likely to fail over time, and that weight cycling is worse than maintaining current weight.”
Simon said she’s had patients with a BMI over 55 who have been turned away from fertility clinics. “Luckily they found other help,” she said, adding that dealing with infertility is already stressful and when women feel guilt and shame about their size, it can affect their mental health. “I’ve had great success working with women with fat bodies who support themselves during pre-conception and post-partum pregnancy. I support them to stand up for themselves and their greatness.”