PDA

View Full Version : Too thin or too fat ...Body weight extremes may affect fertility: study


Welcome to the Active Low-Carber Forums

Support for Atkins diet, Protein Power, Neanderthin (Paleo Diet), CAD/CALP, Dr. Bernstein Diabetes Solution and any other healthy low-carb diet or plan, all are welcome in our lowcarb community. Forget starvation and fad diets -- join the healthy eating crowd! You may register by clicking here, it's free!



doreen T
Wed, Apr-23-03, 21:11
Last Updated: 2003-04-23 15:36:31 -0400 (Reuters Health)

By Jesse J. Logan

NEW YORK (Reuters Health) - Extremes of body weight -- being either very thin or obese -- may decrease a woman's chance of getting pregnant through in vitro fertilization (IVF), according to new research.

In a study of 372 women undergoing IVF at a South Carolina hospital, researchers found that those who were underweight and overweight had lower pregnancy rates than normal-weight women.

While normal-weight women became pregnant about half of the time, underweight and overweight women conceived about 35 percent of the time.

"I think those are the real key points to our study," study co-author Dr. William R. Boone told Reuters Health. "Women really need to pay attention to their body weight if they want to get pregnant," said Boone, who is at the Greenville Hospital System.

The researchers looked at the women's body mass index (BMI), a measure of weight in relation to height used to gauge underweight and obesity. They took into account known factors that affect IVF success, such as age and hormone levels.

During IVF, a woman's eggs are harvested and then fertilized with a man's sperm in the laboratory. The resulting embryos are then transferred into the uterus.

In the study, the researchers gave various doses of hormones to stimulate the uterus. Then, they transferred the embryos -- usually about three at a time.

Embryos were more likely to take hold in the uterus in normal-weight women than in underweight or overweight women, the researchers report. Referring to the lining of the uterus, Boone said that if an embryo doesn't "stick in there, you don't get pregnant."

Underweight women had a BMI of less than 20, which would be a weight of about 120 pounds for someone who is 5'6" tall. Overweight women were those with a BMI of 28 or more, which would be a weight of about 175 pounds for a woman who is 5'6" tall.

Overall, underweight and overweight women were about half as likely to get pregnant as normal-weight women.

"Even in a very controlled environment, when it comes times to implant, these embryos don't do quite as well in these thinner women," Dr. Paul B. Miller, co-author of the study, told Reuters Health. "Likewise, with the heavier women."

The researchers conclude that underweight and overweight women might suffer from hormonal imbalances or dysfunction during ovulation that could affect IVF. But the jury is still out. They point out that "controversy still exists concerning the effect of extremes of BMI and IVF success."

Some studies have found no effect of body weight on IVF pregnancy rates, while others have found a negative effect only when women were overweight.

One theory, the researchers note, is that in very thin women, low levels of the chemical leptin, a natural regulator of body weight released by fat cells, may affect the discharge of eggs from the ovaries.

"So if you have low fat stores, you'll have low levels of leptin, which won't allow for normal communication between brain and pituitary and will cause problems for ovulation," Miller said.

In overweight women, one possibility is that "metabolic derangements" or problems associated with obesity, such as high cholesterol, heart disease and diabetes, affect fertility. "So one would think that pregnancy would be an additional demand on them and be more prone to failure," Miller said.

Or, Boone said, "Maybe it's just simply too much estrogen. Your fat is directly related to your estradiols," which are a form of estrogen.

While the researchers noted that future studies are "in order," they said underweight and overweight women can take steps to increase their chances of IVF success.

Miller suggested that very thin women may want to cut back on their fitness regimes and try to increase their body weight, while overweight women could experience "marked impact if they can lose 10 to 15 percent of their body weight in some circumstances" from dieting and exercise.

"All we know is that overweight and underweight, if you can try and find your way into that middle range, your pregnancy rates improve significantly," he said.

SOURCE: Fertility and Sterility 2003;79:645-646.


http://www.reutershealth.com/archive/2003/04/23/eline/links/20030423elin007.html