We are what we eat, as the cliché goes. But that saying doesn’t hold true for infants — they are what Mom eats. And increasingly in the Western world, parents’ diets are often packed with cheap vegetable oils and other unhealthy ingredients from processed foods.

Now scientists are discovering that it isn’t just our own bodies we put at risk with our dietary choices. The food we eat, even before having kids, can also play a role in the health of our offspring. (Dads don’t get a pass here, either. There’s strong evidence that a father’s diet matters, too – more on that later.)

The latest evidence comes from a study in Communications Biology, a journal from the prestigious journal Nature. Researchers found that when moms have an unhealthy balance of fatty acids, it can make their children more likely to end up obese (Sakayori et al., 2020).

Fatty acids in foods come in four basic types: saturated, monounsaturated, polyunsaturated, and trans fats. In adults, some are thought to increase the risk for certain health conditions, like heart disease.

Not all fats are bad though. Polyunsaturated omega-3s are vital for the health of many living things. They’re a basic component of our cells, propping up many of our body’s functions and promoting good health (NIH ODS, 2005). However, our bodies can’t make omega-3s on their own. Instead, we have to get them in our diets, mainly from seafood. Wild-caught salmon, mackerel, and sardines are all excellent sources of omega-3s.

There’s also another important kind of polyunsaturated fat called omega-6s. In the American diet, most of these fatty acids come from seed oils. Commonly, these are “vegetable oil” (which is nearly always soybean oil) and canola, sunflower, and safflower oils.

However, unlike with omega-3s, eating too many omega-6s can lead to negative health consequences. And studies have sounded the alarm in recent years about how the processed foods popular in Western diets are skewing the ratio of omega-6 to omega-3 fatty acids (NIH ODS, 2005). Research suggests that the risk of cardiovascular disease and other health issues goes up as your omega-6 to omega-3 ratio increases (Simopoulos 2008).

Omega-6 to Omega-3 Ratio

Based on that connection, scientists in this latest study fed pregnant mice a diet high in omega-6 fatty acids and low in omega-3s, then watched how their offspring fared. Compared to control mice who got fed a normal diet, the offspring of omega-6-rich rodents were more likely to be overweight (Sakayori et al., 2020).

The researchers say that the weight problems likely stemmed from fetal changes in dopamine systems, which respond positively to food. As a result, the young mice got a stronger “high” from eating sugary, fatty foods, which led them to overeat. Meanwhile, the offspring of the control mice did not gorge on unhealthy foods, even when the scientists offered them.

Of course, these mice were given omega-6 fatty acids in levels no human would ordinarily experience in their diet. Instead, the idea was to lay a foundation for future studies in humans (Hiroshima University, 2020).

If this trend holds up in people, it might offer a new strategy for preventing childhood obesity. Instead of focusing on treating children once there’s a problem, parents could try to avoid obesity problems before they appear. Physicians could simply recommend that pregnant mothers avoid foods high in omega-6 fatty acids the way expectant parents are already encouraged to avoid alcohol today.

What We Eat, Children Inherit

The finding also conforms to recent studies suggesting that foods parents consume and are exposed to during pregnancy, or even before, can have a lasting impact on the child.

In recent years, researchers have discovered that Mom’s diet can alter a child’s genes and even play a role in whether or not her child ends up a picky eater. But it’s not just Mom’s choices. For decades, studies have been finding hints that dad’s lifestyle also plays a role in their baby’s health, even before a child is born (Wallock et al., 2001). Scientists have shown that exercise, proper vitamin levels, and even a man’s body temperature can impact his child’s well-being. If Dad isn’t eating healthy, it can increase the chances of a miscarriage and birth defects, or even alter the child’s long-term health (Lambrot et al., 2013).

For example, in another study in mice, scientists from the University of Nottingham in England fed rodent fathers-to-be a poor-quality diet low in protein and watched to see if it affected their progeny (Watkins et al., 2018). The offspring were more likely to be overweight and suffer symptoms of type 2 diabetes, the researchers found. By analyzing the rodent’s DNA, they discovered that the lack of protein led to changes in the DNA in the males’ sperm and altered how genes are expressed in their offspring.

And even if you’re not expecting to have children soon, there are other good reasons to avoid excess omega-6 fatty acids and consume enough omega-3s. A 2017 study found evidence that exposure to omega-3s early in life can help reduce the risk of allergies (Miles and Calder, 2017). In contrast, the same researchers showed that eating too many omega-6s might make allergies worse. The relationship seems to stem from the way these fatty acids help mediate inflammation and immunity in the body.

So it’s no surprise that the researchers in this latest study showed that Mom’s diet can help or harm a baby’s long-term health. And these results only reinforce how important it is to pay attention to what we’re putting in our bodies.

Eat Fish, Avoid Processed Foods

Across human history, our ancestors ate a diet with a ratio of about one to three parts omega-6 fatty acids to one part omega-3s (Simopoulos 2002). But today, modern diets have shifted away from regular seafood consumption and include growing levels of processed foods. The average American diet now includes at least 10 times more omega-6s than omega-3s, according to the National Institutes of Health (NIH ODS, 2005). And while the NIH also says the issue needs more study, it does recommend that people “should consume more omega-3 and fewer omega-6 fatty acids for good health."

Even fish aren’t created equal when it comes to omega-6s. Increasingly, when Americans eat fish, it comes from a fish farm. All Atlantic salmon on the market are now raised in captivity, for example. And as it’s gotten harder for farmers to source the feeder fish for their salmon food, they too have turned to cheap vegetable oils as an alternative source of fat (Khan et al., 2017). In 2016, the BBC reported that omega-3 levels in farmed salmon had dropped by as much as half over the previous five years. At the same time, farmed fish have seen increases in their already-high omega-6 levels.

Boosting your omega-3 levels isn’t hard. These fatty acids are found in many different kinds of seafood, and are especially abundant in wild-caught salmon. They’re also commonly available in omega-3 supplements.

On the other end, an easy way to avoid over-consuming omega-6s is to simply steer clear of processed foods, especially deep-fried versions such as fast-food chicken, fries or potato chips, whenever possible. It’s challenging to avoid seed oils when eating out, so cook for yourself whenever possible using butter, or olive or coconut oil. Meal prep might take a bit longer, but the results will be tastier and healthier.


Sakayori, N., Katakura, M., Hamazaki, K. et al. Maternal dietary imbalance between omega-6 and omega-3 fatty acids triggers the offspring’s overeating in mice. Commun Biol 3, 473 (2020). https://doi.org/10.1038/s42003-020-01209-4

National Institutes of Health - Office of Dietary Supplements, Omega-3 Fatty Acids and Health: Factsheet for Professionals. 2005

Simopoulos A. The omega-6/omega-3 fatty acid ratio, genetic variation, and cardiovascular disease. Asia Pac J Clin Nutr. 2008;17(S1):131-134. doi: 10.1684/ocl.2010.0325

Calder PC. n-3 polyunsaturated fatty acids, inflammation, and inflammatory diseases. Am J Clin Nutr. 2006 Jun;83(6 Suppl):1505S-1519S. doi: 10.1093/ajcn/83.6.1505S. PMID: 16841861.

Hiroshima University. "Offspring of mice fed imbalanced diets shown to be neurologically 'programmed' for obesity." ScienceDaily. ScienceDaily, 4 September 2020.

Wallock LM, Tamura T, Mayr CA, Johnston KE, Ames BN, Jacob RA. Low seminal plasma folate concentrations are associated with low sperm density and count in male smokers and nonsmokers. Fertility and Sterility. 2001;75(2):252-259.

Lambrot, R., Xu, C., Saint-Phar, S. et al. Low paternal dietary folate alters the mouse sperm epigenome and is associated with negative pregnancy outcomes. Nat Commun 4, 2889 (2013). https://doi.org/10.1038/ncomms3889

Adam J. Watkins, Irundika Dias, Heather Tsuro, Danielle Allen, Richard D. Emes, Joanna Moreton, Ray Wilson, Richard J. M. Ingram, Kevin D. Sinclair. Paternal diet programs offspring health through sperm- and seminal plasma-specific pathways in mice. Proceedings of the National Academy of Sciences, 2018; 201806333 DOI: 10.1073/pnas.1806333115

Miles, Elizabeth A, and Philip C Calder. “Can Early Omega-3 Fatty Acid Exposure Reduce Risk of Childhood Allergic Disease?.” Nutrients vol. 9,7 784. 21 Jul. 2017, doi:10.3390/nu9070784

A.P Simopoulos, The importance of the ratio of omega-6/omega-3 essential fatty acids, Biomedicine & Pharmacotherapy, Volume 56, Issue 8, 2002, Pages 365-379, ISSN 0753-3322, https://doi.org/10.1016/S0753-3322(02)00253-6.

Khan KU, Zuberi A, Fernandes JBK, Ullah I, Sarwar H. An overview of the ongoing insights in selenium research and its role in fish nutrition and fish health. Fish Physiology and Biochemistry. 2017;43(6):1689-1705. doi:10.1007/s10695-017-0402-z