The low-carbohydrate Paleo diet has attracted star advocates, including professional golfer Phil Mickelson, actor Matthew McConaughey, and Republican presidential candidate Jeb Bush. But experts are now debating whether or not people in the Paleolithic Era did actually eat carbs.

A University of Chicago study published in August suggests that carbohydrate consumption, especially in the form of starch found in plant root tubers, like those found on potatoes, was vital for the acceleration of brain growth over the last 3 million years. And some nutritionists say this is more evidence that a modern low-carbohydrate version of the Paleo Diet may not be the healthiest alternative, even if it does help people lose weight.

The goal of the Paleo diet is to consume the same food groups as our hunter-gatherer ancestors, whose nutritional practices between 2.6 million and 10,000 years ago helped form our modern genetic makeup. These foods include fruits, vegetables, grass-fed meats, fish, seafood, free-range eggs, nuts and seeds. The diet discourages frequent consumption of dairy, starch and processed foods.

Despite the modern diet’s effectiveness at helping some people lose weight, the findings from the study suggest that these may not be the only foods our long-ago ancestors ate.

“Eating meat may have kick-started the evolution of bigger brains, but cooked starchy foods together with more salivary amylase genes made us smarter still,” the study concluded.

The study says that to truly eat Paleo, starch and higher levels of carbohydrates are necessary. It explains that the human brain uses about a quarter of the body’s energy budget and about 60% of blood glucose — energy needs that wouldn't have been met on a low-carbohydrate diet. Additional glucose was necessary for pregnancy and lactation. The study also found evidence that the genes that code for the enzymes needed to digest starch evolved about 1 million years ago, in the midst of the Paleolithic era, further suggesting a diet that included significant levels of starch.

Thus, the study concludes, the Paleo diet’s exclusion of starch doesn't take into account the role it played in the development of the modern genome.

“Up until now, there has been a heavy focus on the role of animal protein and cooking in the development of the human brain over the last 2 million years, and the importance of carbohydrate, particular in form of starch-rich plant foods, has been largely overlooked,” the study found. Researchers at the University of Chicago compiled archaeological, anthropological, genetic, physiological and anatomical data to study the prominence of carbohydrates in Paleolithic era humans for the study.

As obesity rates rise, the weight-loss market has become a growing industry. The commercial diet industry was a $2.5 billion market in 2014, and is expected to grow at an annual rate of 5.5% for the next five years, research firm IBISWorld estimates.

Interest in the Paleo diet concept, which reportedly originated in 1985 in a paper published in the “New England Journal of Medicine,” has also surged. Google searches for the term “Paleo diet” increased steadily between 2009 and 2012, and peaked in 2013 — dubbed the “year of the Paleo” due to the proliferation of books, blogs and online recipes. With advocates ranging from famous athletes to politicians, the diet has been able to sustain its popularity.

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Paleo diet experts, however, aren’t convinced by the study’s findings. “[Starch] is a poverty food and has little place in the modern diet meant to save you from the constant, huge stream of glucose and simple starches in our modern world,” Arthur De Vany, author of “The New Evolution Diet: What Our Paleolithic Ancestors Can Teach Us about Weight Loss, Fitness, and Aging,” writes in an email interview.

De Vany disagrees with the suggested role of starch and carbohydrates in the study, saying that nutrition from seafood and other prey was the key to rapid brain development, or encephalization.