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Experts recommend a diet of fruits, vegetables, and whole grains as opposed to processed foods. AUSTIN LORD/Stocksy
  • Researchers say eating more like prehistoric people did can lower your risk of heart disease and diabetes.
  • Scientists studied Turkana people who live in northwest Kenya. They found that those who have moved to the city have lower health scores than those who maintain their traditional lifestyle.
  • Experts say our bodies have adapted over time to human diets but haven’t changed to match today’s diet of processed foods and sugars.

In the United States, almost 40 percent of adults have obesity.

More than 30 million adults have been diagnosed with heart disease, and about 1 in 10 have diabetes.

However, rising rates of obesity, heart disease, and diabetes — largely driven by diet — are not solely an American phenomenon, but a global issue on the rise for decades.

The World Health Organization estimates that in 2016, almost 2 billion adults worldwide were overweight or obese.

One theory behind why obesity rates have grown so significantly is the “mismatch theory,” which argues that what humans eat has evolved over millennia to process a certain diet that no longer matches the diets that people have been eating over the past 50 years.

Testing that theory is the aim of a new study in the journal Science Advances.

The research looked at the Turkana people, a population from northwest Kenya that has seen a split in its population from those who still follow a traditional subsistence lifestyle and those moving to the city and adopting a more modern diet.

That gave scientists a unique insight into the direct effects of switching to a diet close to what many human ancestors ate — a native diet, so to speak — and the kinds of foods much of the world eats today.

Looking at 1,226 adult Turkana in 44 locations, the researchers found that those Turkana still living their traditional pastoral lifestyles scored high on all 10 biomarkers for health, including cardiometabolic health.

Those living in cities, however, had poorer health biomarkers, including higher rates of obesity, heart disease, diabetes, and high blood pressure.

The differences also showed a correlation between how long various Turkana had been living in cities and an increase in these lower health scores.

“Humans evolved in a very different environment than the one we’re currently living in,” Amanda Lea, a lead author of the study and a postdoctoral research fellow in the Lewis-Sigler Institute for Integrative Genomics at Princeton, said in a press release.

“No one diet is universally bad,” Lea continued. “It’s about the mismatch between your evolutionary history and what you’re currently eating.”

“Tragically, the modern diet exploits the body’s natural tendency to ‘plan for the future,’” said Benjamin J. Bikman, PhD, a metabolic research scientist and associate professor of physiology and developmental biology at Brigham Young University in Utah.

“When following a traditional style of living, including the traditional diet, food isn’t abundant. Thus, the body is built to store energy when it can to prepare for a future time where food may be scarce,” Bikman said. “In our modern environment, the abundance and consistent access to processed foods mean that our bodies are saving energy for a period of scarcity that never arrives.”

The Turkana’s original diet is just one among many possible diets that ancestral people might have followed, so we shouldn’t extrapolate too widely from this one study, said Dr. Dexter Shurney, president of the American College of Lifestyle Medicine and chief medical officer at Foodsmart, a telenutrition and healthy eating company.

But there are pieces we can take away to help inform our understanding of what a less mismatched diet might look like.

“Most ancestral diets were likely more plant-based than the Turkana tribe. Asians have eaten diets where the stable has been rice for centuries, the Incas potatoes, the Mayans and Aztecs corn, the ancient Egyptians wheat,” Shurney told Healthline. “The major difference is the amount of processed foods we now consume.”

He noted a study from Northwestern University in 2019 that estimated that 71 percent of the U.S. diet was “ultra-processed.”

“Processed food is typically higher in salt, calories, fat, and has less fiber and other nutrients necessary for optimal health,” Shurney said. “Additionally, it tends to wreak havoc on our gut microbiome. Our ancestors certainly ate diets that were unprocessed.”

Sara Patton, RDN, a registered dietitian at the Deborah Heart and Lung Center in New Jersey, agreed.

“The evolutionary mismatch theory has some validity to it. We as humans had evolved so quickly with developing technology to produce and save food beyond anything our ancestors could have done,” she told Healthline.

“This rapid change did not give our bodies time to adapt to the new eating style, or the different chemicals and additives that are now used in everyday food products,” she said. “If anything can be taken away from the study in Turkana, it is that the modern diet should be shifted closer back to the ‘ancestral’ diet.”

Ultimately, that means following the advice that health professionals have been making for a long time, she said.

Consume more whole grains, organic fruits and vegetables, grass-fed wild animals, and healthy natural fats such as olive oil and avocado oils.

Eating more whole grains, fruits and vegetables, and healthy fats is already the bedrock of many healthy diets that experts already recommend.

Among them are the low carb, whole-food diet, the Mediterranean diet, and the Paleo diet, to name a few.

In other words, we know what people should do as individuals, but that knowledge isn’t being translated to lowering global obesity, diabetes, and cardiovascular disease rates.

Commentary within the study itself points to this.

“Indigenous populations that have recently transitioned to market-based economies show higher rates of obesity and metabolic syndrome compared to subsistence-level groups,” the authors write. “Extreme mismatches between the recent evolutionary history of a population and lifestyle are needed to produce the chronic diseases now prevalent worldwide; in the Turkana, this situation appears to manifest in urban, industrialized areas but not in rural areas with changing livelihoods but limited access to the market economy.”

“Our modern food environment is not conducive to health,” said Nicole Avena-Blanchard, PhD, an assistant professor at Mount Sinai Medical School in New York and a visiting professor of health psychology at Princeton University in New Jersey.

“Sure, we live longer than our ancestors did, but that is partly due to the fact that we have medicine to keep us alive when we develop diet-induced health conditions (like cholesterol medications, or diabetes medications),” she said.

“I think we are better off championing for a systemic change in how we approach our diets in general,” she told Healthline. “Part of the problem is that the health consequences of a processed food diet often take a while to manifest, so people don’t always attribute their medical problems to their diet.”