Here's what's wrong with Paleo diet

A recent theory has underpinned the Paleo diet, a high-protein, low-carbohydrate diet that has grown in popularity.

How exactly our brains, which take up about 2 percent of our body mass, but consume 25 percent of our energy, got so big is not known but one theory holds that with the invention of stone tools, we began scavenging for animals and started digesting their protein-rich meat easily and all of those calories gave our brain the surplus energy needed to grow larger, PRI reports.

Refuting the idea that we should eat as our Paleolithic ancestors did, the new paper says meat doesn't hold the key to our large brains. It was the glucose in starches, like potatoes and tubers, cooked over a fire that allowed our brains to grow.

Glucose is the best most readily processed form of energy in our diet, says co-author Mark Thomas of University College London. "So that's what our Paleolithic ancestors would've wanted because without it, they're going to die."

Thomas argues that we started cooking with fire about 800,000 years ago, earlier than many scientists believed in the past. Cooking is very important as it has a profound effect on the ability to access the energy density in starch-rich foods, Thomas says, adding that it also helped in evolving enzymes in our saliva that broke down cooked starches.

Disagreeing with the paper, the creators of the Paleo diet argue that carbohydrates (like starches) weren't necessary for the evolution of our brains.

But Thomas draws a distinction between the Paleo diet, which he calls a "trademarked dietary regime," and academic research into how our ancestors ate, by saying that the Paleolithic period, which really means the period in which we made stone tools before farming, is a very long period and encompasses many periods and environments and ecologies, thus there was never one single Paleolithic diet.

He agrees with one of the central tenets of the Paleo diet though - that we eat more carbohydrates than we need, but says the dietary issues of our Paleolithic ancestors were quite different, adding that people are still not clear exactly what they ate.

The study is published in The Quarterly Review of Biology.