Are High-Fat Diets Healthy? New Study Reveals New Truths

by Amanda Oliver
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Are High-Fat Diets Healthy? New Study Reveals New Truths

Key takeaways:

  • The keto diet has become popular, but high fat diets may not be as good for you as they claim.
  • A recent study with mice* found that diets high in fat can lead to obesity, diabetes, and other health issues.
  • Particularly, soybean oil—compared to coconut oil and commonly found in processed foods—may have a negative impact on health.
  • Moderating fat intake and focusing on whole foods like fruits, vegetables, and lean protein is important for staying healthy.
  • While fat is necessary, it should be consumed in moderation from healthy sources like avocados, nuts, and seeds.
  • Unhealthy fat consumption can impact the immune system and brain function, and exercise alone may not offset its effects.

Keto this, keto that. Grocery store aisles are filled with “keto-friendly” alternatives to their carb-filled counterparts and every other Instagram health guru seems to be touting the benefits of going low carb. The keto diet has become one of the most popular out there, with some 23 million Americans following it in 2022, according to Harvard. But are high fat diets actually as good for you as they claim to be?

A recent study conducted by the University of California, Riverside revealed some surprising new truths about consuming a diet high in fat — and it’s not great news for the keto evangelists.

TL;DR: Even if you aren’t eating steak and eggs for every meal or blending butter into your morning coffee, you could be eating too much fat.

Here’s what that could mean for your well-being.

What the study found

Researchers fed mice diets of more than 40 percent fat—which sounds like a lot, but is closer to the standard American diet than you might think.

“Most Americans consume about 40% of their calories from fat sources when the recommendation is 25-35%,” Stephanie Tarnacki, RD, says, adding that most of that comes from processed foods and animal products, which can be very high in saturated and trans fats.

In this study, the mice were given either conventional soybean oil (polyunsaturated fat), modified soybean oil similar to olive oil (monounsaturated fat), or coconut oil (saturated fat).

After 24 weeks, the researchers extracted intestinal tissue to examine the gut microbiome and used a method called RNA sequencing to determine any genetic changes. They found that:

  • Soybean oil induces obesity, diabetes, insulin resistance and fatty liver disease.
  • Soybean oil also negatively impacted gut health and affected genes related to autism, Alzheimer’s disease, depression, and more.

It’s not a surprise given that science has long proven that high fat diets can increase the risk of cardiovascular disease and hypertension, along with a slew of other health issues.

“This study indicates that a high fat diet—regardless of animal or plant source—may also put you at risk of colon cancer, dysbiosis of your microbiome, decreased immunity and increased risk of obesity, Type 2 diabetes and fatty liver disease,” Tarnacki explains.

Not all fat is created equal

While the study concluded that a diet high in fat—no matter the type or source—can have detrimental health effects, some sources of fat are worse than others. In the context of this research, soybean oil proved to be more harmful than coconut oil.

Also Read >> MyFitnessPal’s Essential Guide to Fat

And, according to the USDA, soybean oil is the most commonly produced and consumed edible oil in the United States. It’s found in everything from salad dressing to frozen foods.

“When it comes to type of fat, soybean oil had the greatest negative impact on gut health, and the largest impact on risk factors for obesity, insulin resistance and risk for Type 2 diabetes,” Tarnacki cautioned.

What this means for how we eat

While it’s true that no diet is one-size-fits-all, moderating your fat intake is crucial in staying healthy, according to the research.

Tarnacki recommends eating a primarily whole food plant-based diet full of fruits, vegetables, whole grains, and lean protein (like fish, turkey, and chicken). Limit the amount of processed food you consume, as packaged snacks and foods are often high in saturated fat.

Also Read >> How to Build a Healthier Plate

That said, fat is still a necessary macronutrient with all sorts of benefits — it helps your body absorb vitamins and nutrients, keeps your hormones healthy, and so much more. But moderation is key, Tarnacki says. She suggests incorporating healthy sources of fats from whole foods like avocados, nuts, seeds and olives.

Bottom Line: Health Starts With What You Eat
If you think you can just run an extra mile on the treadmill to offset over-consumption of unhealthy fat, you may want to reconsider.

“Regularly eating this way could be impacting your immune system and how your brain functions,” Poonamjot Deol, UCR microbiologist and co-first author of the study, said. “You may not be able to just exercise away these effects.”

*Mice and other animal studies are not always credible predictors of human reactions to the same exposure.

Unsure how much fat you’re consuming daily? Start tracking with MyFitnessPal (for free)!

About the Author

Amanda Oliver
Amanda has more than a decade of experience in commerce and media, specifically in product testing and service journalism in the lifestyle, health and wellness, and outdoor space. Amanda is currently the Executive Editor of Commerce at Field & Stream. She is also an RYT-200 yoga teacher and NASM CPT personal trainer when she’s not at her desk. Both a foodie and fitness junkie, Amanda currently writes for a number of outlets like People, Real Simple, Taste of Home, Milk-Drunk, and Mind Body Green.


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