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One of my friends swears by the Paleo diet. Does this diet work? Should I try it? – JL, San Diego, CA

Thanks for the question. Let’s get right to it!

The so-called paleo diet is a modern fad diet in which people eat foods that were (supposedly) only available to cavemen during the paleolithic period of human evolution. The idea here is that cave man & cave women were in great shape and didn’t suffer from modern diseases like diabetes and heart disease. Adherents hold that humans evolved to eat this way and the rapid change to a diet high in cereals and dairy, fueled by modern agriculture, has led to all the obesity and many of the health problems we have today. Most modern paleo diets are high in fruits, vegetables, meat, seafood, nuts and seeds, while being low (or containing no) cereals, grains, dairy, legumes (including peanuts), salt and potatoes.

So before we get to whether the diet “works”, let’s talk about the theory around it. Did humans evolve to eat like the hunter-gatherers of the paleolithic age? Was this diet preventing diabetes and heart disease while keeping them in great shape? Do we even know what people form the paleolithic age ate? The answer to all of these questions, I’m afraid, is a resounding no.

Let’s start with the paleolithic age itself. It was very different from our time, and things really weren’t as simple as a bunch of folks living in caves gathering food. The paleolithic age lasted about 2.5 million years, and only ended 12,000 years ago. It ended with the invention of modern agricultural practices (farming and raising livestock). During most of the paleolithic, there were no humans – at least no homo sapiens. Instead there were homo habilis, who were quickly replaced by homo errectus, who were in turn pushed aside by homo neanderthalensis (Neanderthals), who were then usurped by our crafty homo sapien (modern human) ancestors. Homo sapiens have only been around for 300,000 years, and the Neanderthals went extinct only about 40,000 years ago. These humanoids were well into the paleolithic age before they figured out how to cook anything with fire, and fishing using anything other than spears was only invented about 20,000 years ago. The modern continents were generally similar to today (give or take 50 miles), but they were alternatively covered in huge glaciers during successive ice ages. There weren’t many of these humanoids around (at most 1 per square mile), and they also didn’t live very long. Infant and child mortality was very high, such that the average person only lived to about 30 years old. However, if you made it to 15, you could expect to live about 50 years.

We don’t know much about what the humanoids ate back then, but you can be pretty sure there wasn’t much variety in most places. Remember there is no agriculture yet, and no trading or significant food storage. People ate what was around them. In some places that might have been mainly fish, in some places (particularly northern latitudes), it was mainly meat, while in others is was mainly fruits and berries. Many foods we take for granted now and some might consider “paleo” were very different from those of today (many wild nuts and tubers were poisonous), restricted to very small areas (squash and pumpkins were only in Mesoamerica, carrots only in the Middle East, watermelons in southern Africa), just weren’t eaten yet (most beans), or simply didn’t exist (broccoli, cabbage, and cauliflower). The same is true for the meat people ate – for almost all people of the paleolithic period, big game hunting was out of the question – it was simply too dangerous using only spears. Pork and beef were almost never eaten. Instead, meat probably came form small animals. To make things more complicated, there is evidence that some human paleolithic populations did in fact eat some legumes, and even dairy (definitely from reindeer, maybe other animals).

If you add it all up, there is no way a modern paleo diet is representative of an actual paleo diet – there is too much variety, and it includes too many things that true “caveman” would never have seen in his or her life, much less eaten. This effectively debunks the argument that humans evolved to eat this diet so it must be healthier, since the two diets have little in common. Plus, this assumes that humans haven’t evolved in the last 12,000 years (almost  500 generations), which is silly – that’s plenty of time for significant changes in the function of the human digestive tract to adapt to our new diets.

So is it true that this diet will prevent modern “diseases of affluence”? This is also almost certainly untrue. There are a host of reasons people didn’t get diabetes and heart disease back in the paleolithic age – mainly because they didn’t live long enough, but also because people were very active (hunting and gathering) and exercise is extremely beneficial in the prevention of these diseases. Also, who’s to say that some of the older paleo humans didn’t get diabetes and heart disease? Without modern medicine, they would have quickly died, and their death would have been indistinguishable from any other ailment of the time.

Will it help you lose weight? That all depends. As UYBFS often depressingly reminds you, there is one, and only one way to lose weight, and that is to eat fewer calories than you burn. If you cut your calories and/or increase your amount of exercise, you’ll lose weight on this diet and almost any other. If you eat 3,000 calories of meat and berries a day while sitting on your couch, you will gain weight just as fast as you would eating the same calories from McDonald’s.

Fear not, JL, it’s not all bad news! For the most part, the paleo diet is a healthy one. A diet high in fruits and vegetables with little to no processed food is a great idea, so as diets go, it’s not a bad one to try. Just keep in mind that you still have to watch your calories if you want to lose weight. As with all diets, you’ll do better if you add regular exercise. The only caution is that the strict paleo diets tend to be very low in calcium, which can be dangerous, particularly for women. This is easily remedied with by taking a calcium supplement. I know, I know, cavemen didn’t have calcium supplements, but there is a reason you don’t see a lot of cavemen around these days – we know a lot more about health an nutrition than they ever did.

So what’s the bottom line? The paleo diet can be a healthy alternative to diets high in processed foods and simple sugars, which are risk factors for metabolic disorders like obesity and diabetes. Add in some exercise and calcium supplements and it could help you lose weight and feel healthier. However, don’t buy into the “eat like a caveman” thing, and don’t let anyone tell you people evolved to eat a chicken stir fry with kale, zucchini, olive oil and lemon. This sounds healthy – and it is – but it would have been impossible for a paleolithic age human to eat. The modern chicken didn’t exist yet (if you lived in southeast Asia, you could have eaten it’s progenitor, the red junglefowl), kale didn’t exist yet, nor did zucchini (and it’s ancestors could be found only in Mesoamerica), and nowhere on earth could you have found both lemon and olives in the same place. You get the point.