Dr. David L. Katz, director of the Yale University Prevention Research Center, was on the 22-person panel. While he did not personally rank the Paleo diet last in the overall weight-loss category, he did raise several issues about what the diet actually means. He noted that our Stone Age ancestors gathered more than hunted by most accounts, and had a mostly plant-based diet.
"The meat our Stone Age ancestors ate is nothing like the meat we eat today," said Katz. "When's the last time you saw a mammoth? I rest my case."
While Katz said the idea behind it is indeed a good one, in this day and age, it could easily be misinterpreted.
"It is the dietary pattern to which we are adapted -- our native diet -- and as such, almost certainly informative about what's good for us," Katz said. "But ... it's easy to turn the concept of Stone Age-style eating into an excuse for hamburgers, and that certainly won't do your health any good."
While Keith Ayoob, associate professor of pediatrics at Albert Einstein College of Medicine in the Bronx, N.Y., said he has "no problem with people eating plenty of lean protein and fresh fruits and vegetables," he did have a problem with the lack of whole grains and low-fat dairy.
"I can't recommend a diet that advocates exclusion of whole foods groups, and foods like low-fat yogurt and milk and beans and whole grains," Ayoob said. "As for dairy, a lifetime of no dairy and you're really risking osteoporosis and low bone density. Paleo man didn't have to worry -- he'd be dead by age 40, but the rest of us would like to hang out for considerably longer and have strength while we do."
But Cordain argued that dairy is not a necessary diet staple, and said questioning its absence is a "kneejerk" response in the medical community. He said 65 percent of people are lactose intolerant, and it wasn't until relatively recent times that humans even began drinking mammals' milk.
"They lived outdoors so they had a lot more sun exposure," Cordain said. "Their blood concentration of vitamin D was likely higher, which enhanced the calcium absorption in their diets.
"We always are thinking more more more calcium, but it's just as much about the amount of calcium we absorb as how much we're putting in our bodies," he said. "This notion that all you have to do is put more into your system is incorrect."
Dr. Lynda Frassetto, professor of medicine at University of California at San Francisco, has conducted research on the Paleo diet. While she did not research the weight loss possibilities of the Paleo regimen, she did say that people on a strict Paleo diet lowered their cholesterol and lipids and their insulin improved.
Paleo diet advocates argue that obesity and diabetes didn't occur 10,000 years ago, so the eating habits and lifestyles are worth exploring for a modern-day approach to these epidemics.
While Ayoob argues that the Paleolithic man didn't live long enough for such problems to occur, as most died around 35 or so, they did eat locally and perform high amounts of physical labor, things Ayoob said he could get behind.
"Of course, if people did that much physical activity, they probably wouldn't be obese in the first place," Ayoob said.
"Physical activity is often a deciding factor for much of our chronic health problems," he said. "Much of type 2 diabetes is obesity related and instead of focusing only on diet, we need to focus on activity also, because physical activity can affect insulin resistance, body weight, cholesterol and triglyceride levels, joint health, and so on. Without that, there can be no balanced lifestyle."