July 1, 2008 Mothers who eat an unhealthy diet during pregnancy may be putting their children at risk of developing long term, irreversible health issues including obesity, raised levels of cholesterol and blood sugar, according to new research(1). The study, carried out in rats and funded by the Wellcome Trust, suggests that the effect is even more pronounced in female offspring.
A study published last year carried out by the same team at the Royal Veterinary College, London, showed that rodents which ate a diet rich in fat, sugar and salt whilst pregnant were more likely to give birth to offspring that overate and had a preference for junk food when compared to the offspring of rats given regular feed.
Now, in a follow-up study published in The Journal of Physiology, the researchers have shown that a mother's diet has an effect lasting beyond adolescence in the rats, even when the offspring were weaned off the junk food, affecting how their bodies metabolise the food and suggesting a long term health impact.
Dr Stephanie Bayol and her colleague Professor Neil Stickland compared the offspring of rats fed a diet of processed junk food such as doughnuts, muffins, biscuits, crisps and sweets during pregnancy and lactation, and compared their offspring with those fed a healthy diet of regular feed.
The offspring of the mothers fed junk food diets had raised levels of cholesterol as well as higher levels of triglycerides, a type of fat found in the bloodstream. Both are known to increase the risk of developing heart disease. Similarly, the offspring had higher levels of glucose and insulin, both of which increase the likelihood of developing type 2 diabetes.
The researchers studied the rats beyond adolescence through to adulthood and observed that the rats were still fatter than those whose mothers had eaten a healthier diet whilst pregnant and breastfeeding. Crucially, this partly manifested itself as increased fat mass surrounding the kidneys relative to body mass; this so-called perirenal fat is also involved in the development of insulin resistance and type 2 diabetes.
"It seems that a mother's diet whilst pregnant and breastfeeding is very important for the long term health of her child," says Dr Bayol. "We always say 'you are what you eat'. In fact, it may also be true that 'you are what your mother ate.' This does not mean that obesity and poor health is inevitable and it is important that we take care of ourselves and live a healthy lifestyle. But it does mean that mothers must eat responsibly whilst pregnant."
Although the study was only carried out in rats, Professor Stickland believes the findings are likely to be applicable to humans. A 2007 US study published in the American Journal of Obstetrics & Gynecology(2) showed that the more weight that pregnant women put on, the higher the risk that the child would be obese children. A 2005 British Medical Journal(3) study also showed a correlation between parental and child weight.
"Humans share a number of fundamental biological systems with rats, so there is good reason to assume the effects we see in rats may be repeated in humans," he says. "Our research certainly tallies with epidemiological studies linking children's weight to that of their parents."
One surprising find from the study was how the maternal diet disrupted the offspring's metabolism: male offspring whose mothers had gorged on junk food had higher levels of insulin and normal levels of glucose, whilst the opposite was true for female offspring, who also tended to be fatter.
In addition, female offspring showed higher levels of leptin, a hormone related to appetite. It is already known that female appetite is more sensitive to leptin and male appetite to insulin, both of which the body can become resistant to. This suggests that metabolism is different for the two sexes and that the offspring's bodies will have a tendency towards over-eating.
"Obesity has increased dramatically over the last few years and needs to be tackled urgently," says Dr Pat Goodwin, Head of Pathogens, Immunology and Population Health at the Wellcome Trust. "This study supports the idea that there are many different risk factors that can lead to someone being overweight and developing related health problems. Pregnancy can be a difficult time for many mothers, but it is important that they are aware that what they eat may affect their offspring."
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- Bayol et al. Offspring from mothers fed a "junk food" diet in pregnancy and lactation exhibit exacerbated adiposity which is more pronounced in females. The Journal of Physiology, 2008; DOI: 10.1113/jphysiol.2008.153817
- OKEN et al. Gestational weight gain and child adiposity at age 3 years. American Journal of Obstetrics and Gynecology, 2007; 196 (4): 322.e1 DOI: 10.1016/j.ajog.2006.11.027
- Reilly et al. Early life risk factors for obesity in childhood: cohort study. BMJ, 2005; 330 (7504): 1357 DOI: 10.1136/bmj.38470.670903.E0
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