The "Paleo", or Paleolithic diet, is one of the trendiest modern diets. Also known as the "hunter-gatherer diet" or the "caveman diet", the Paleo diet attempts to approximate the diet of our human ancestors, millions of years ago. If you're just starting to hear about the Paleo diet, here's an overview of its main tenets.

The Pre-Agricultural Diet

The Paleo diet focuses on foods that our Stone Age ancestors would have eaten, before the Agricultural Revolution. This includes mainly foods that can be hunted, fished, or foraged, such as grass-fed meats, wild-caught fish, fresh vegetables, nuts, and seeds.

The theory is that our hunter-gatherer ancestors were free of what are commonly known as the "diseases of affluence" — cancers, cardiovascular disease, obesity, autoimmune diseases, dental caries, and diabetes. Therefore, products of the Agricultural Revolution are frowned upon on the Paleo Diet. As the Paleo philosophy goes, humans started experiencing negative health outcomes in the Neolithic period when they started consuming large amounts of:

• dairy
• grains such as wheat, corn, oats, and rice
• beans and legumes
• refined and processed oils
• refined sugars

These foods should therefore be excluded from the diet.

Paleo supporters point to modern hunter-gatherer societies — such as the Kitava people on Papua New Guinea, who typically have low rates of chronic disease — as evidence that the Paleo diet is healthier than the Western diet.

Using an evolutionary argument, proponents of the Paleo diet suggest that human genetics are best adapted to the hunter-gatherer diet, and have not yet evolved to thrive on more recent agricultural products.

A Low-Carb Diet

In practice, the Paleo diet does generally turn out to be a lower carbohydrate diet, primarily due to the reduction in grain consumption. It also tends to be a high protein diet, with plenty of grass-fed and organic meat and seafood. However, the Paleo diet should be distinguished from other low-carb diets, such as Atkins, in its emphasis on the quality and variety of the foods chosen. All refined and processed foods should be avoided (no diet shakes!), and followers of the Paleo diet should eat a wide variety of whole foods: fruits and vegetables, nuts, seeds, and healthy proteins.

A larger proportion of meats and nuts also means that the Paleo diet tends to be higher in fat than the US government-recommended diet. However, proponents of the Paleo diet say that those fats are healthier fats (from grass-fed meats, seafood, avocados, and nuts rather than from junk food and hydrogenated oils) with a higher proportion of heart-friendly omega-3 fats.

Results of the Paleo Diet

Preliminary studies and anecdotal evidence show that many people on a Paleo diet experience metabolic benefits such as weight loss, lower rates of triglycerides, lower blood pressure, and better glucose sensitivity. However, critics say that those benefits may be conferred simply because of lower caloric intake, and a lower consumption of refined sugar and processed foods.

Critics also say that the tiny number of studies done on the Paleo diet cannot foretell what the long-term health consequences of the Paleo diet will be, and whether or not it confers any unique health benefits.

The Paleo Diet in Practice

You can decide how "primal" to make your diet. If you're having trouble cutting out all grains, adding a little rice or quinoa back into your diet may make the transition easier. If you can't quite cut out all dairy, having a little yogurt or cheese may just ease the way. There are no hard and fast rules, though there are plenty of guidelines and recipes out on the web for Paleo or less-restrictive "primal" diets. You should also maintain at least a moderate level of exercise.

The Paleo diet can get expensive — after all, grass-fed meats and wild-caught seafood aren't cheap, especially when they have to fill the void left by grains and legumes. It can also be time-intensive, because you are supposed to cook all of the food yourself and there are few convenience foods that fit the guidelines. However, many people who follow the Paleo diet say that the added expense and effort pays off with better energy levels, weight loss, and better overall health.