While undoubtedly there are a number advantageous health aspects to the "Paleolithic diet" as it's portrayed in the popular media, there are also a number of dangerous nutritional fallacies and oversimplifications hidden within it. This isn't an indictment of dust's writeup, but rather an attempt on my part to amplify the beneficial aspects of the diet and provide some careful warning concerning the hidden dangers.
1) "Hunter-Gatherers ate lots and lots of meat"
a) Actually, hunter-gatherers probably ate less meat, significantly less, than the usual American "commuter diet" (fast food). Current surveys of American eating habits show that most people are eating fast food 4-5 times a week. This is almost inevitably beef, the fattiest, most cardio-deleterious meat out there. The profile of fats in beef is heavily slanted towards the "bad" artery clogging type. This is particularly true of factory farmed beef, given the livestock's own intake and lack of exercise. Attempting to emulate the diet of early man by eating a wagonload of factory-farmed beef, without calorie counting, until satiation, would be nutritional disaster.
b) The meat early man ate was game, and they ate many different species and cuts of meat. When physical anthropologists call homo sapiens an omnivore, they mean it. Arboreal mammals like squirrel and small monkeys were likely fare, along with dog, wild pig, deer and other ungulates. This was food of the fly, lean and wild. Very little saturated fats, and typically yielding only a small serving of edible meat per "takedown". Early man would have eaten the organs, like kidneys, brain, liver, and tongue, which most Americans are not in the habit of eating. Early man ate these tissues for the micronutrients - Vitamin C, E, etc. In northern climes, these meats are often the only way to avoid deficiency diseases like scurvy. Also, any riparian or coastal H-G's were probably eating large quantities of fish. Fish is fantastically good for you, most types containing the much-touted omega-6 fatty acids. These "good" fats actually scour harmful cholesterol from the bloodstream. The native Americans of the Pacific Northwest, and tribes of the Ohio River Valley consumed massive quantities of fish. Archeologists have recovered paleolith landfills, a short walk from old village sites. These fills contain tons, literally tons, of fish bones. Red meat was recovered in quantities that lead anthropologists to speculate that it was mostly a "feasting" food.
c) Early man may have eaten his share of meat, but most of his calories still probably came from carbohydrate foods gathered by the women of the tribe. One groundbreaking study of the !Kung by Richard Lee, an anthropologist, discovered that 2/3rds of calories consumed by the tribe came from nuts gathered by women. The Ache of Ecuador get the bulk of their calories from wild tubers and root vegetables, like carrots. The remainder was meat and other wild vegetables gathered by the men and women. This comes close to the 30/30/40 Diet eaten by triathletes, cyclists and other athletes. That's 30% of your daily calories from fat, 30% from protein, 40% from carbohydrates - a profile somewhat distant from the one outlined as the "paleolithic diet". It's also supported by holistic medicine practitioners such as Dr. Andrew Weil. More on the kind of vegetable intake (carbohydrates) probably eaten by Paleolithic man in a moment.
2) The diet is pointless without the exercise
It isn't just that early man ate different quantities of meat. It was a lot of exercising bringing in that meat, gathering those nuts, berries, and root vegetables. For just a quick comparison, consider bowhunters and gun hunters. There is no shortage of fat hunters that use modern long rifles to bring down deer (my experience is specific to the eastern US). That's because when you put a 30.06 soft point through a buck at 2000 feet per second, they drop dead. Walk over an pick up your new dead deer.
Now consider bowhunters. You won't see as many of the generously proportioned here. Why? Bows usually kill through hemorrhage - massive blood loss. An instant kill is almost impossible. This translates down to hitting the deer, then tracking its blood trails until it dies. This can take miles, over rough terrain. This is serious exercise.
The situation is even more drastic for actual hunter-gatherers. Returning to the !Kung , the men could range as much as 30 to 40 miles a day, with a combination of running and walking. Groups indigenous to northern Mexico would hold tribal runs, where over a period of 48 hours, the men of the tribe would track entire heads of deer or buffalo until their prey would literally drop dead from exhaustion. These groups could cover more than 100 miles during these super-runs. The women and children would follow behind, gathering the dead and dressing them on the march. To say that this reflects a fitness level somewhat above the sedentary American lifestyle is something of an understatement. Pushing a "Paleolithic" diet, minus the very substantial exercise level that should attend it, is an absurdity.
3) Comments on glycemic index, privation and the Atkins diet.
Finally, the kinds of vegetables early man ate included wild grains. After all, what constituted the starter stock for our current-day domesticated crops? These wild grains were usually crushed and then cooked in an unleavened state - like a tortilla or hardtack. These coarse ground grains were loaded with complex carbohydrates that could take hours to metabolize - providing daylong energy, and in concert with proteins and good fats, generating high level of sustained energy by creating a steady blood sugar level.
A new way of looking at carbohydrate intake is glycemic index. Corn on the cob and white sugar are both carbohydrates, both complex and simple. Eat the white sugar and it's in your bloodstream in 15 minutes. Your body takes all that it can and warehouses the rest as fat. Eat the corn on the cob, and it takes your stomach all afternoon break down corn into usable sugar. The energy gets used, not offlined into fat. The speed with which a given carbohydrate food is converted into blood sugar is called the glycemic index. Low glycemic index foods, like traditional style oatmeal, "stick to your bones". Snickers bars and other such high sugar foods spike your blood sugar and then crash it. Placing the two classes of foods in the same forbidden category is not just fallacious, it invites the believer to turn her back on a great, healthy energy source, and a cornerstone of an intelligent diet. Carrots, corn, fruit, leafy greens, and complex carbohydrates like WHOLE grains and beans are all low glycemic index. Eat and enjoy them!
If you cut 15% off your caloric intake and ran/walked 90 minutes a day, you'd be lean as a rail in 6 months (ok, 12-18 months if you're really overweight). If you stuck to a natural foods 30/30/40 diet, you could cut that 15% overhead and windup feeling like you had more energy than you started with. The exercise would change your body composition, so that you could occasionally treat yourself to fun foods like ice cream. Super simple diets are oversimplified diets. Intelligent eating must be married to careful research, personal experimentation, and above all, exercise. There is a contrarian aspect to the salesmanship surrounding many of these radical diets that appeals to people looking for big changes in their life. Caveat Emptor
Enjoy what you eat, eat well, exercise, avoid "computer ass" and live!