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The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
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More than 26 percent of American adults were obese as of 2009—compared with less than 20 percent in 2000, according to a new report from the U.S. Centers for Disease Control and Prevention. And the number of U.S. states with more than 30 percent of their population topping a body mass index (BMI) of 30 tripled between 2007 and 2009. With this accelerating epidemic, researchers are looking for clues beyond daily diet and exercise to explain our propensity for extra poundage—and many are finding evidence in the very first stages of life.
A growing number of analyses have found a convincing link among a heavier mother-to-be, increases in her baby's birth weight, and the child's later risk of obesity. In many past observational studies, however, basic genetics or environmental factors could be blamed for this association.
A new study of 513,501 mothers and 1,164,750 of their children born across 15 years aimed to take genetics out of the equation by assessing maternal and infant weight only for those women who had more than one child. "By making comparisons of two or more infants born to the same mother, we were able to factor out the role of genetics," says David Ludwig, an associate professor of pediatrics, director of the Obesity Program at Children's Hospital Boston and co-author of the new study.
Women who gained more than 24 kilograms during a pregnancy (which occurred in about 12 percent of pregnancies) added an average of 147.4 additional grams to their baby's birth weight than those who gained about 7.5 to 10 kilograms. In other terms, pregnant women who gained 22.5 kilograms had double the risk of having an infant with a high birth weight compared with those who only gained about nine kilograms. And every kilogram gained during pregnancy increased a baby's weight by about 9.5 grams, according to the analysis, which published online August 4 in The Lancet.
Being heavier at birth increases the odds that an individual will be overweight or obese as a child—as well as an adult. And the excess weight has been linked to a range of chronic conditions, including asthma, diabetes and metabolic syndrome (a group of metabolic risk factors).
Although previous studies had correlated high BMI moms with heavier babies, "the direct effects of excessive weight gain on the fetus have never been conclusively demonstrated," notes Ludwig, who worked on the study with collaborator Janet Currie, a professor of economics at Columbia University.
The importance of grams
The ill effects of undernourishment on fetal development have been well documented. A pregnant woman who does not get ample calories for her and her fetus increases the risk the baby will have stunted physical growth, poor cognitive development, and be more susceptible to diseases. The health risks of too many calories, however, are just beginning to come to light.
To be sure, a heavier fetus will tilt the pregnant mother's scale slightly, and the amount of weight typically put on my moms gaining too much during pregnancy far exceeds the additional ounces their babies typically take on.
Nevertheless, although 0.2 kilogram of additional baby fat might not sound like much, in the context of a three- to 3.5-kilogram infant, every 0.03 kilogram changes the odds ratio, according to Ludwig.
Other research indicates that infant birth weight is also heavily determined by a woman's weight even before she becomes pregnant. A study published in June in the European Journal of Pediatrics reported that being overweight or obese before getting pregnant meant that a mother's future child was 1.4 times more likely to be overweight or obese by age four. "It means preconception health screening and intervention for overweight and obese [women] is extremely important," says Panagiota Kitsantas, an assistant professor of biostatistics and epidemiology at George Mason University's Department of Health Administration and Policy and lead author of the June paper.
Although her investigation did not specifically look at women with more than one child and thus could have been colored by other genetic and environmental factors, Kitsantas says that the results from her work and The Lancet report are complementary. "Both studies pointed to one direction: mothers' body weight affected their offspring's weight."
Underlying changes
Extra birth weight might not be the only change many of these infants face. Excessive maternal weight during pregnancy is also likely changing the metabolic and hormonal environment of the developing fetus, Ludwig says.
Even if an infant has a few extra ounces due to a mother's excessive gestational weight gain, "the infant developed in a metabolically abnormal intrauterine environment," Ludwig explains.
Excessive caloric intake by a pregnant woman can stimulate the overgrowth of fetal tissues, change hormonal balances, alter metabolic pathways, "and perhaps even structures in the brain that regulate appetite and metabolism," he says. And those changes might stay with an individual for life.
Many adults have a difficult time losing weight and keeping it off, and if the body is predisposed to putting on the pounds, fighting obesity on both individual and societal levels will be even more challenging.
Researchers are still working to understand just how some of these pathways and hormones can influence disease risk, primarily through animal studies in the lab. And until more chemical links are found, a direct cause-and-effect relationship cannot be established, Kitsantas notes.
She applauds the new work, noting that Ludwig and colleagues used apt statistical models to try to avoid confounding effects and excluded subjects with other risk factors such as gestational diabetes or extremely high birth weight. Kitsantas is not entirely convinced, however, that genetics can be erased from the picture, and asserts that more lab work remains to be done to parse out nature, nurture and nutrition.
Prepregnancy health
Not every baby born on the heavy side will battle obesity or related chronic diseases. But, Ludwig points out, "on a population basis, [increased birth weight] is shifting risk upward."
The amount of weight pregnant women are putting on has been growing—as has their prepregnancy weight in the past few decades, Ludwig notes. Alongside that trend are signs that average birth weight is also headed upward.
"If we don't stop the vicious cycle at some point, we'll just keep going and going," Kitsantas says. If female babies are born more prone to obesity, the likelihood of their gaining too much weight before or during pregnancy increases, thus putting their offspring at greater risk.
Even though the specific mechanisms at work remain poorly understood and there is still not enough evidence to draw a cause-and-effect conclusion between maternal weight and a child's risk for obesity, Kitsantas says that is not reason enough to delay action. "We really have to jump in based on the findings we have to create specific interventions to fix the problem."
Ludwig acknowledges that the challenge of getting Americans to stay fit is great but says that changing the habits of mothers-to-be might be a little easier. "Women tend to be especially motivated during pregnancy because it's not just their health [that is] at stake—it's their children's," he notes. "Almost every mother instinctively wants to give their children a healthy start in life."
And, along with physical activity, food quality is just as important as quantity, he says. "The higher quality of diet consumed, the easier it is to maintain a health body weight," says Ludwig, who has been working on a new study comparing the effects of two different diets on maternal and infant health. "The best time to begin obesity prevention efforts for the next generation is actually prior to birth," he says.
Kitsantas extends that recommendation, suggesting that all women of childbearing age establish healthy lifestyle habits and healthy weights: "The sooner the better," she says.
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10 Comments
Add CommentI'd even speculate that there's a strong correlation between obese mothers and obese children. That the mother was obese during pregnancy does not preclude childhood obesity due to household dietary influences, disregarding any potential causal effects during pregnancy or hereditary factors.
Reply | Report Abuse | Link to thisA statistical analysis of the surrogate mothers and their offspring would more definitively determine the causal relationship between obesity during pregnancy and childhood obesity. No, I'm not kidding!
It says 1.4 chance of having overweight or obese if parent is overweight before getting pregnant. I was underweight, and both my kids are overweight. I am now average for a 64 yr old, but my daughter is not obese, but without a doubt over weight.
Reply | Report Abuse | Link to thisHer doctor has not said a thing to her. So, who is responsible for the genetics of this? One brother and I were the only thin people in my immediate family. Most of our extended family were all overweight, not obese. Only 3 cousins were underweight, or average. The men did not have this problem.
I don't know what the problem is but no one has correlated the amount of Antidepressants used by the US population.
Esp. SRRI's which are notorious for adding 30 lbs to an average person. And it is weight that cannot be worked off.
I have tried. I just have to wonder how many drugs that we take are ONE of the reasons behind this current epidemic.
I have never seen so many obese/over weight people as I have been seeing in the past 10 yrs. It can't be JUST exercise, and diet.
The people doing experiments need to look at the amount of SRRI's taken by people who are obese/overweight. This pills are being given to all of us, and most are putting on an additional 10-30 lbs within 3 months. This weight is always a problem, and the dr's say: "either live with the weight or go back to depression"...........so is that a factor that has not been looked at in this period of extreme weight gain.??
Reply | Report Abuse | Link to thisMore preparatory propaganda to get you ready to accept the food police telling you what you can and cannot eat.
Reply | Report Abuse | Link to this@frgough: congratulations, that was one of the most ridiculously stupid comments I've ever read!
Reply | Report Abuse | Link to thisIs the REAL cause of obesity the TOXINS that are overburdening our bodies so that our organs, especially the kidneys, cannot eliminate them fast enough? The next line of defense for the body is to encapsulate those toxins in fatty tissue. Why isn't anyone studying this angle? Makes more sense than blaming it on mom's weight.
Reply | Report Abuse | Link to thisObesity occurs when the amount of food consumed exceeds the amount of energy expended. There are many reasons that encourage obesity the main being excess consumption of processed foods which have high fat or sugar content and low nutritional elements. Also less physical workout and activities lead to obesity. Not only these factors but some cannot be blamed as it is also generic and may be acquired due to heredity.
Reply | Report Abuse | Link to thishttp://www.fightobesity.net/obesity-in-children.html
Im not sure what SSRI you are taking but weight gain is not a major side effect of most SSRI medications. They are notorious for sexual side effects. They may cause gastrointestinal issues, or sleep disturbance, and weight gain can be a side effect. But as a physician, and a patient who takes an SSRI, weight gain is not a side effect I have read about occuring very frequently, nor have I seen it in my patients as a poblem with SSRIs very often. weight gain IS a notorious issue with antipsychotics which are often used in combination with SSRIs for severe or resistant depression.
Reply | Report Abuse | Link to thisAnd as for why our country is gaining weight so much. It is just about diet and exercise. However, that is not nearly as simple as it sounds. It involves our entire culrural lifestyle from being more sedentary, being more busy, larger portion sizes, etc. If you are interested in understanding this better I recommend the book the Weight of the Nation. It explains a lot about why it is so hard to lose weight, why we gain weight, and the various aspects of society and our daily lives that make it such a challenge for so many of us. It is a great book, (I believe they also did something on HBO, though I have not seen that. ) It is written in a very easy to understand way, and was for me at least very enlightening on just how complex the problem is.
please excuse my typos in the previous comment, I am typing this on a phone...
Reply | Report Abuse | Link to thisResearch has recently been suggesting that the amount of weight gain during pregnancy, as well as the pre pregnancy weight/health of the mother can effect the child's chances of becomeing obese later in life. I beleive this is what this article is getting at. We ar born with a certain number of fat cells. This number can grow, but it can not shrink. When a person looses weight they do not lose the number of fat cells they have, they simply shrink the fat cells they already have. The question that researchers are interested in is what impact the prenatal environment has on the amount of fat stores a baby is born with as well as any changes in gene expression that may occur in an overly nutrient rich prenatal environment that may make it more likely for them to become obese. This area of questioning is rather new, but so far there seems to be something to it. It appears that there may be a real connection between maternal obesity and childhood obesity besides basic genetic makeup and home eating environment. whether this is a real observation or an artifact of science is yet to be determined, but either way it is only one of many factors in the obesity epidemic. this issue was brought about due to a large variety of reasons/causes, and will only be improved by addressing a wide variety of aspects as well.
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