How much weight should I lose before conceiving?

What does the evidence say about weight loss amount before trying to conceive while trying to conceive?

1. A 16-week NIH-funded trial in women with obesity and unexplained infertility, whose intervention group lost an average of 6.6 percent of body weight through diet and exercise, found no significant difference in live birth rates compared with a group that did exercise alone, leading the lead researcher to say the evidence does not support recommending preconception weight loss for this specific outcome. 1
2. A review of randomized controlled trials on lifestyle interventions for women with overweight or obesity notes that other research has linked a 2 to 5 percent reduction in body weight with restored ovulation, and found the clearest improvement in pregnancy-related outcomes among women with a starting body mass index of 35 or higher rather than those at a lower starting weight. 2
3. A pilot randomized trial set a preconception goal of losing about 5 percent of starting body weight in women with overweight or obesity, and a structured meal-replacement program helped participants reach an average of 5.3 percent loss over 10 weeks, compared with 2.8 percent in the group that received conventional dietary advice. 3
4. In a randomized trial of women with a starting BMI of 27 or higher, those in a prepregnancy weight-management program were 73 percent less likely to have gestational diabetes at early pregnancy screening than a usual-care comparison group, though the gap between groups narrowed by the standard 24 to 28 week screening point. 4
5. Weight matters for both partners: a systematic review found men with obesity had markedly fewer normal motile sperm than men at a healthy weight in one study, plus lower testosterone and higher sperm DNA fragmentation, about 20 percent in men at a healthy weight versus roughly 27 percent in men with obesity. The review uses the standard adult categories of 18.5 to 24.9 as a healthy BMI, 25 to 29.9 as overweight, and 30 or above as obesity. 5

What to know about weight loss amount before trying to conceive while trying to conceive

• Early planning is the lowest-pressure window for gradual change. Structured programs that pair a modest calorie reduction with regular activity have helped women with overweight or obesity reach roughly a 5 percent body-weight loss over several months, a steadier pace than a rapid diet. Loop in your provider before starting, especially with a BMI of 30 or higher.
• Once you are actively trying, know that a specific number on the scale is not a guarantee of a faster pregnancy. A large NIH-funded trial found that women with obesity and unexplained infertility who lost an average of 6.6 percent of body weight through diet and exercise did not have higher live birth rates than a group that did exercise alone. Ask your provider what still makes sense for your plan at this stage.
• Later in the process, the same individualized approach still applies. Some research ties preconception weight loss to a lower chance of gestational diabetes once pregnancy begins, but there is no single pound or percentage figure that fits everyone. Once a pregnancy is confirmed, the goal shifts from weight loss to the weight-gain guidance your provider gives you.