Your Grandma's Diet Could Have Made You Obese, Mouse Study Suggests

The negative side effects of gorging on a high-fat diet could be passed on to great-grandchildren, a study involving mice has suggested.

Rodents who were fed a fat-heavy diet were more likely to have pups that were obese and insulin-resistant, even if they were not obese themselves, researchers found.

The mouse equivalent of addictive behaviors toward drugs also appeared to be inherited by offspring. Even great-grandchildren were affected, with females more prone to addictive behaviors and males experiencing obesity. Researchers noticed this trend in third-generation mice whose parents weren't given high-fat food.

The team conducted the study, published in the journal Translational Psychiatry, by splitting mice into two groups. One was fed a high-fat diet for nine weeks, including before, during and after pregnancy, while the second stuck with regular feed. Male offspring of high-fat mothers were mated with females who ate regular rat chow. This process was repeated to produce the great-grandchildren of the original mice.

To test whether the mother's high-fat diet affected her offspring's risks of overeating, obesity and addictive behaviors, as well as her grandchildren's risks, variables such as the animals' insulin and cholesterol levels, weight, insulin, sensitivity and metabolic rates were noted.

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While the paper has given a glimpse into the inner workings of mammals, the results don't translate directly to humans.

Study author Daria Peleg-Raibstein of the Laboratory of Translational Nutrition Biology at ETH Zurich told Newsweek: "It's quite a large step to apply conclusions from mouse studies to humans. However, studying effects of maternal overeating are almost impossible to do in people because there are so many confounding factors, such as socioeconomic background, parents' existing health conditions."

Peleg-Raibstein added, "Many people also have underlying genetic risks of obesity and addiction that have nothing to do with environmental factors that your forebears might have been exposed to. However, because this is a mouse study, we need to be careful about drawing conclusions for humans."

If evidence proving this link in humans can be produced, eating unhealthily during pregnancy could be regarded as damaging, just as smoking and drinking are.

"This study suggests that though it's completely normal to eat more, eating too much junk food might have consequences that may last for generations," she said.

Mascha Davis, a registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics, told Newsweek, "There are many other factors that can contribute to gene expression and predisposing factors to obesity and addiction."

The study is important, however, "because it shows us that what a mother eats before, during and after pregnancy can potentially play a huge role in her children's and grandchildren's health, specifically their weight and risk for addiction," she said. "Also, it tells us that what we eat can influence gene expression."

She was particularly interested to read that a high-fat diet predisposed the offspring to obesity, even when the mothers themselves weren't overweight.

Danielle Reed of Philadelphia's Monell Chemical Senses Center told Newsweek that past studies on the heritability of obesity have overlooked the idea that overeating could reshape the brain's reward pathways.

She said, "It is easy to think in narrow terms about personal responsibility—what we do affects only ourselves—but this study suggests that what parents do can have effects at least two generations hence."

As 9.3 million people in the U.S. are obese, understanding the genetic basis for the condition could be an important tool for tackling the epidemic and resulting conditions such as Type 2 diabetes, cardiovascular disease and mental health conditions.

Earlier this year, scientists wrote in The BMJthat being genetically predisposed to obesity is not a proven barrier to maintaining a healthy weight.