Mom’s Obesity During
Conception Phase May Set The Stage For Offspring’s Obesity Risk
New
data suggest that maternal body composition at or near conception has
important implications for offspring’s obesity
BETHESDA, MD – The number of overweight and
obese Americans continues to grow rapidly. Today, 50 percent of adults are
overweight and up to 20 percent are obese. While the number of
overweight/obese children is at an all time high, the steady increase of
overweight infants – individuals under 11 months old – is alarming.
Research studies have found that pregnant women who are
overweight/obese are more likely to give birth to heavier babies, and the
risk of overweight children becoming obese adults is nearly nine times
greater than for children who are not overweight. Studies also show that
greater body-weight at birth and weight gain early in life increases the
risk of becoming overweight or obese as an adult. Inheritance studies show
that a child’s body mass index (BMI) correlates more closely with the
mother’s BMI than with it’s father’s, suggesting that an interaction of both
genetic and intrauterine influences, may contribute to later-life obesity
risk in the offspring.
Armed with these and other data, a team of researchers
from the USDA-Arkansas Children’s Nutrition Center has examined whether the
subtle effects of fetal exposure to the mother’s obesity can have a latent
effect on the offspring. In a new report, investigators studied whether
fetal exposure to gestational obesity leads to a self-reinforcing viscious
cycle of excessive weight gain and body fat which passes from mother to
child. The results of the new study suggest they do.
The Study
The study is entitled, “Maternal Obesity at Conception
Programs Obesity in the Offspring.” It was conducted by the research team of
Kartik Shankar, Amanda Harrell, Xiaoli Liu, Janet M. Gilchrist, Martin J.J.
Ronis and Thomas M. Badger, all of the Arkansas Children’s Nutrition Center,
Little Rock, AR. Their findings appear in the online edition of the
American Journal of Physiology – Regulatory, Integrative and Comparative
Physiology (doi:10.1152/ajpregu.00316.2007). The journal is one of 11
published each month by the American Physiological Society (APS;
http://www.the-aps.org/).
To test the theory that obesity in adulthood may be
subject to programming during fetal development, the researchers developed
an overfeeding model which was used in rats. The model allowed the
investigators to replicate many of the metabolic and hormonal features of
overweight human individuals. They were also able to exclude parental
genetic influences, match gestational weight gain, limit the exposure of
maternal obesity in utero, and control lactation efficiency, all of
which can be difficult confounding variables in studies with human
subjects.
Summary of Methodology
Virgin female rats were fed liquid diets via enteral
nutrition at one of two caloric levels: (1) the caloric level recommended by
the National Research Council (187 kcal/kg3/4/day) or (2) a level
of 15 percent overfeeding (220 kcal/kg3/4/day).
In the preliminary experiments, the rats consuming the normal caloric intake
had weight gains similar to controls while those being fed the obesegenic
diet had become substantially overweight. Body weights were monitored three
times a week and body composition was analyzed non-invasively on a regular
basis.
To examine the long-term gestational effects of
maternal obesity on the offspring, lean (n=7) and obese (n=15) rats were
allowed to mate with normal (lean) male rats for a period of one week.
Following mating, all female rats (lean and obese) received respective diets
at 15 percent excess calories per day in order to ensure adequate caloric
intake for pregnancy. Maternal body weights were monitored three times a
week and all rats gave birth naturally. Offspring born to lean or obese
rats were raised by surrogates who were fed regular rodent diets to
ascertain the pups’ obesity exposure was limited only during gestation.
The male offspring from each group were weaned from the
surrogate mother at 21 days after birth and fed (by giving unlimited access
to) either a normal diet or a high-fat diet. The pups’ body weight, body
composition and other factors were analyzed for 130 days. At day 130
additional samples were taken and analyzed, to include organ weights,
glucose and triglyceride levels, fat cell size, body composition and
hormones.
Key Findings
The researchers found the following:
-
at birth, the weight of the offspring from both groups was
similar. The number and size of pups and the ratio of males to females
did not differ significantly.
-
the amount of calories the pups consumed (relative to
their body-weight) at the 60- and 120-day mark suggested that both
groups consumed the same amount of calories, indicating no effect of
maternal obesity on the offspring’s food intake.
-
when both the lean and obese offspring were fed a control
diet, their body weights remained similar. However, when both groups
were fed a high-fat diet, the obese offspring gained remarkably more
weight, suggesting that exposure to maternal obesity led to programming
of increased susceptibility to obesity in the offspring, which was
revealed following an obesegenic challenge despite a normal birth
weight.
-
when both groups were fed a control diet, obese offspring
had a ~ 1.6 times greater fat ratio compared to their lean offspring
counterparts. Further, obese offspring fed a high-fat diet had a 26
percent greater percent fat ratio and a 60 percent increase in
subcutaneous fat mass vs. lean offspring.
-
high fat feeding significantly increased serum glucose,
triglyceride, insulin and leptin levels in both groups. Strikingly, the
serum insulin and leptin levels increased by 2.2 and 2.3 fold in obese
offspring compared to lean offspring fed the same diet.
Conclusions
These findings add to the existing body of evidence
showing that both maternal obesity and genetic background influence
offspring’s susceptibility to obesity. It goes further, to highlight the
role of post-natal obesegenic diet as a determinant in revealing subtle
programming imposed by maternal obesity. The results also demonstrate that
high levels of adiposity (body fat) occur in the offspring of obese mothers
despite consuming similar calories as their lean-offspring counterparts and
that offspring obesity is associated with insulin resistance. The
“programming” of susceptibility to obesity occurs in the absence of changes
in birth weights and other fetal outcomes.
According to Dr. Kartik Shankar of the Arkansas
Children’s Nutrition Center, “The mother’s body composition at conception
has important implications for the metabolism and risk of obesity in the
offspring in later years. Not only do these findings help us appreciate the
reasons for the rapid rise in obesity, this novel model will allow us to
understand the underlying mechanisms and should provide fertile opportunity
for translational type research.”
# # #
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society (APS;
www.The-APS.org) has been an integral part of the scientific discovery
process since it was established in 1887.
***
NOTE TO EDITORS: To schedule an interview with
a member of the research team, please contact Donna Krupa at 301.634.7209
(direct dial) or
DKrupa@the-APS.org.
Key words: Obesity, pregnancy,
developmental programming, body composition, adipose tissue; American
Physiological Society
