One of the woes of our modern lifestyle and eating habits has been the development of the obesity epidemic. There are many medical conditions caused by or worsened by obesity, such as diabetes, heart disease, stroke and infertility. Recently there have been several studies demonstrating the negative impact of obesity on reproduction.
Pregnancy rates in obese women may be as much as 30% lower than those of non-obese women with otherwise similar characteristics.
We also know that obese women can be less responsive to fertility medications. For the same medication dose, obese women often produce less eggs than normal weight women.
What is obesity?
A standard medical definition of “normal” body weight is a body mass index (BMI) of 18.5 – 24.9
- A BMI under 18.5 indicates that the person is “underweight”
- A BMI of 25.0 – 29.9 indicates that the individual is “overweight”, but not obese
- A BMI over 30 indicates obesity
- A BMI over 40 indicates extreme obesity.
The BMI is calculated based on a person’s height and body weight. That being said, BMI calculation does not take into account percent body fat, so theoretically someone with lot of muscle mass could have a higher BMI but not have the same negative health consequences as someone with the same BMI but much higher percent body fat.
Why does obesity cause infertility?
The main culprit in the metabolic manifestations of obesity is the increased number of fat cells. The extra fat can cause insulin resistance, leading to type-2 diabetes and an increased production of male-like hormones which, in women, can lead to ovulation disorders. In obese women, there are increased inflammatory processes in the body that can contribute to infertility, increased risk of miscarriage, as well as other unrecognized metabolic abnormalities. Not only do women that are obese have a more difficult time getting pregnant, but once pregnant, they also have a higher risk of miscarriage and giving birth to babies with birth defects. While maintaining a healthy weight is important, one does not have to aim towards becoming a size 2 supermodel. Even just a 5%-10% weight loss can significantly improve the chances for successful conception.
How can I lose weight?
I always recommend a healthy, balanced diet and moderate exercise. Stay away from “Fad” diets as they are not sustainable. The goal is to lose the weight and keep it off, which may involve a complete change in the way one approaches food. Consider the advice of a professional dietician. Think about signing up for a program like “Weight Watchers”, “Jenny Craig” etc., since structured programs can often make the difficult task of losing weight a little easier, providing discipline and emotional support. A healthy rate of weight loss while trying to conceive is acceptable, but be sure to discuss the plan with your doctor and get the help and support you need. Weight loss can dramatically improve your chances of success, regardless of which infertility-treatment option is chosen.
When is bariatric surgery appropriate?
If a woman has been unsuccessful with diet and lifestyle modifications and still has a BMI greater than 35-40, bariatric surgery can be considered. Often, in people with a BMI over 45, bariatric surgery in conjunction with lifestyle modifications is needed to effectively lose an adequate amount of weight.
Can one undergo fertility treatments if obese?
The answer is yes, as long as the patient has realistic expectations and is aware of the lower success rates of any fertility treatment in obese patients. Since the age of the woman as well as the egg reserve have a more profound impact on fertility than anything else, it would not be prudent to expect a 40-year-old woman or a woman with a very low egg reserve to lose weight and then come back at a later time, because sometimes the window of opportunity may be lost. It is always my advice to patients to do the best they can to optimize their lifestyle and weight before they start attempting pregnancy or while undergoing treatment. Unless a pregnancy is unsafe for the patient, withholding treatment only based on weight may be an unfair thing to do, especially in older women.