Grandparents' diet could be a weighty issue for grandkids

Male mice can pass on a heightened obesity risk to their sons and grandsons
Aug 31, 2016 — 7:15 am EST

Unhealthy eating today could heighten obesity risks for future generations, a new study finds.


Here’s some bad news for health conscious people. If their parents and grandparents gorged on unhealthy food, they may face an exaggerated risk of weight gain. That’s the finding of a new mouse study. It’s not yet been confirmed that  the same is true in people. But it was a concern over human risks that prompted the new study.

Too little exercise and eating too many calories are root causes of obesity. However, in the past few years, scientists have begun to explore the role of our DNA. Some genes may play a role in making people fat. For instance, studies have shown that some genes can make a person’s body burn calories less efficiently. People with these “fat” genes could find it hard to lose weight.

The latest study, conducted in Australia, adds to those depressing data. It shows that the tendency of some people to become overweight may trace to what their parents or even grandparents ate long before they were born.

That new experiment was conducted in two parts. First, the researchers bred a group of obese male mice with lean females. They also bred a control group with each other. Here, both males and females had a healthy weight.

When male mice that had an obese father were given junk food to eat, they developed a lot of problems. They had higher-than-normal levels of blood sugar, or glucose. They also had an excess of the hormone insulin in their blood. Perhaps worst of all, their livers accumulated too much fat. All of these conditions are generally found in people who are obese, have metabolic syndrome or have diabetes.

Female mice born to obese fathers were not affected. The male mice that had a lean father also showed no problems.

The DNA in the two sets of offspring were the same. This meant that the genes of those obese fathers were not the problem, says Jennifer Cropley. She works at the Victor Chang Cardiac Research Institute in Darlinghurst, Australia. The animals’ genes had not been directly to blame, her team found. Their symptoms of metabolic syndrome instead traced to how or when certain genes were allowed to operate.

Cropley studies epigenetics. It’s the branch of science that looks at how things in the environment, including diet, can affect little “tags” on genes. These tags work like switches to turn genes on and off. And it was those external switches that were somehow altered, Cropley’s group discovered.

What’s more, it wasn’t just the sons of the obese dads that showed this metabolic problem. The grandsons, too, developed the same problems after they ate junk food for a while. And this held even for mice whose fathers had eaten well and maintained a healthy weight.

These findings will be published soon in the journal Molecular Metabolism.

Why was this just a male thing?

When the scientists realized it wasn’t genes themselves that were making the next generation of mice fat, they wondered what was going on. What might be happening during mating that made sons and the grandsons of obese male mice so vulnerable?

They decided to look at the sperm of the male mice. RNA is a type of genetic material. It acts like a watchdog, deciding whether or not its gene gets turned on. The RNA in sperm was different in the sons with obese fathers than in sons with lean dads. “It was always thought that sperm just have DNA,” says Cropley. “But in fact, they have RNA molecules,” she says.

This study will change people’s attitudes toward pregnant women, Cropley predicts. “If you’re pregnant, you’re told you should eat well and not drink or smoke,” says Cropley. “Our results prove that contributions of dads might be just as important.”

Laura Dearden is a researcher at the University of Cambridge in England. There, she studies how early-life factors can affect someone’s appetite. Dearden says the study sends out a warning message: “If you are aware of a history of obesity in your family tree, even if your parents aren't obese, you should be careful what you eat.”

Michelle Holland is a researcher at Blizard Institute in London, England. Like Cropley, she studies epigenetics. Holland says scientists always thought this kind of “non-genetic inheritance” did not occur in mammals. But studies such as this have begun to prove that the previous “assumption was wrong.”

Power Words

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cardiac     arrhythmia An irregular heartbeat. There are several types of arrhythmias; the heart can beat too fast, too slow or in a pattern that’s not normal. Some arrhythmias are mild and have little if any effect; others can be life-threatening.






epigenetic changes    Molecular switches that can turn a gene on or off. Methyl groups — chemical clusters each made of one carbon and three hydrogen atoms — latch onto DNA near a gene. It’s these methyl groups that can alter the programmed activity of a gene, turning it on or off. Individuals can acquire an epigenetic change at any time during their lives

fat     A natural oily or greasy substance occurring in animal bodies, especially when deposited as a layer under the skin or around certain organs. Fat’s primary role is as an energy reserve. Fat is also a vital nutrient, though it can be harmful to one’s health if consumed in excess amounts.

fatty liver disease    A condition that results when too much fat builds up inside the liver. People who are obese or drink too much alcohol risk developing this condition. Left untreated and allowed to worsen, it can eventually lead to life-threatening liver failure.



generation   A group of individuals born about the same time or that are regarded as a single group. Your parents belong to one generation of your family, for example, and your grandparents to another. Similarly, you and everyone within a few years of your age across the planet -are referred to as belonging to a particular generation of humans. The term is sometimes extended to inanimate objects, such as electronics or automobiles.




liver  An organ of the body of animals with backbones that performs a number of important functions. It can store fat and sugar as energy, breakdown harmful substances for excretion by the body, and secrete bile, a greenish fluid released into the gut, where it helps digest fats and neutralize acids.







RNA  (short for ribonucleic acid) A single-stranded molecule inside most of cells that performs a number of functions, including producing protein. RNA molecules can also play a role in the expression of some genes.




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JOURNAL: J. Cropley et al. Male-lineage transmission of an acquired metabolic phenotype induced by grand-paternal obesity. Molecular Metabolism. Accepted June 16, 2016. doi: 10.1016/j.molmet.2016.06.008.