What is a Paleo Diet?

A few people recently have asked me questions about my diet, mainly because I refuse things like cakes, sandwiches and pies when offered them. The diet I eat is most commonly known as a paleo diet, but also goes by its full name, Paleolithic diet, and also Stone Age, caveman or hunter-gatherer diet.

Wikipedia has a page on the subject called Paleolithic diet, but I wanted to summarise things from my perspective. I’ve been eating this way with fairly strict adherence for 7, nearly 8 years, so I’ve got quite a bit of “practical experience”, and I’ve done enough research in that time to satisfy myself that my choices makes sense.

I’m not going to be especially detailed here, I’m not going to be comprehensive (I don’t say much about mental illness or cancer), and I’m certainly not going to reference every claim I make. I’m no biologist, and everything I know about nutrition is from casual part-time research. Treat this entirely as my opinion, as I will state as fact things that many people contest. Assume confirmation bias by default, but read with on open mind.

Why should you care?

I believe that the vast majority of disease we consider mysterious and incurable is caused by a mismatch between the environment we evolved to live in, and the one we have created for ourselves, and that the biggest (although by no means the only) difference is the food we eat. I count among these: heart disease, cancer, diabetes, multiple sclerosis, scizophrenia, Alzheimer’s, even short-sightedness. But this post is an attempt to explain what a paleo diet is, not why I believe it causes all these things, and many more. I will not justify everything here, as that would turn a blog post into a book, and there are already many better ones on the subject.

Other reasons you may care include: you met me in real life and repeatedly tried to offer me pie so I directed you here, or you stumbled across my blog/Twitter bio, saw “paleo” and thought I might be some sort of crazy hippy.

What is a paleo diet?

The principle behind the paleo diet is fundamentally that all biological life thrives best in the environment it evolved in. This is the environment it is best adapted to cope with, even if it could survive in others. For this reason, polar bears survive best in the arctic, camels in the desert, and an exchange of the two will see neither animal survive for long. As well as climate and physical terrain, the kinds of food available to an animal is a major part of what it is adapted to. Again, this is is why rabbits do well eating leaves, lions do well eating meat, and an exchange would be equally disastrous for both.

However, as a civilisation, as a species that has effectively domesticated itself, we humans are remarkably blind to the idea that we evolved to eat certain foods. While I’m fairly sure nobody I’ve ever met would be surprised if a monkey fed on cornflakes, beans on toast, lasagne and ice cream would get sick, my experience is that the thought this could apply to us is met with anything from disbelief to outright hostility.

What food did humans evolve to eat?

Humans are primates, and are omnivorous like many (or most) other primates. As far as I’m aware, we eat comparatively more meat than other primates. We are evolved to eat a wide range of foods, including meat, vegetables, fruits and nuts. The usual paleo rule of thumb is if you could you eat it “naked and armed only with a sharp stick”, although we should probably add “and a big heavy stone” to that, since that helps with eating nuts. Fire has been around long enough that has probably had an influence on our dietary evolution: I consider the ritual of the barbecue fairly strong evidence of that. So my broad definition of paleo is:

Paleo foods are ones you could eat if you were in the wild, naked and armed only with a sharp stick and a big stone, ideally enhanced by cooking

It rolls slightly less easily off the tongue than the original, but it’s more complete.

What foods did humans not evolve to eat?

This part is much more complex, as to understand what we didn’t eat, you have to understand how the foods available to us have changed during the agricultural revolution. What we did not evolve to eat is the foods introduced into our diets in the last 10,000 years, which require agriculture and machinery to process. The main groups here are grains, dairy products (anything derived from milk), legumes (pulses), refined sugars and vegetable oils.


Grains in their natural state are inedible to humans, as they are to most animals. They are physically inedible, being encased in a hard protective husk. They contain many toxins and anti-nutrients, which make eating any quantity of them dangerous. The effect of grains to leech calcium from bones is why they are used by biologists to induce rickets in rats when they wish to study the disease – why it has never occurred to these same scientists that they are staring at the cause of the problem exasperates me.

The proteins in grains, especially gluten, are dangerous to humans, and to people with high sensitivity to them can be fatal.

The other main problem with grains is the high starch (carbohydrate) content. Now, listen very carefully, for I shall say this next bit only once: eating fat does not make you fat, high insulin levels make you fat, and high insulin levels are caused by eating excess carbohydrate, not eating fat. The idea that we need to balance our calories in and calories out to avoid becoming overweight is complete nonsense. The human body is not a combustion engine, and does not work on such a primitive mechanism. All animals are programmed to overeat, to feast in times of plenty to compensate for times of famine. If the calorie theory of weight gain was correct, we would all be morbidly obese, every single one of us, except for the few too poor to afford even an excessive amount of bread.

Dairy products

Dairy products are also a recent introduction to the diet. Most mammals stop producing the lactase enzyme necessary to digest milk around the time their adult teeth have grown; humans are the only one to continue drinking milk into adulthood. And even then, humans don’t drink the milk of their own species into adulthood, they drink the milk of other species. It should come as no great surprise that human milk is best suited to the needs of baby humans, and cow’s milk to the needs of baby cows. Indeed, the protein and fat content of each is considerably different. (Human milk is higher in fat, for a start.)

It is actually cow’s milk that got me on to studying about paleo nutrition, as I have a strong milk intolerance that left me with crippling fatigue until the age of about 22. I gave up milk first, and within 3 days I felt like I’d slept for the first time in over a decade. Sadly neither doctors nor certain family members wanted to believe the connection, but I’ve learnt to ignore people who put their own agendas over the actual real life experience of people affected by degenerative disease. Or as I usually put it: “People who believe something impossible should not interrupt those who are doing it”.

Most of the world’s population is actually lactose-intolerant, and westerners are the exception here. I’m constantly bemused by lactose-free milk and similar products – surely it should be apparent that if so many people can’t digest milk, then it can’t be an essential part of the human diet. I’ve had no milk since I switched to eating paleo, and my bones have yet to start crumbling. (If we needed to drink milk for calcium, the human species would have been wiped out from bone disease literally ages ago. We would simply not be here.) There’s more than enough calcium in vegetables and nuts, and (of course), bones: sardines are an excellent source of calcium as the small soft bones are easily digested. But you can give a lamb chop or chicken leg to a small child and get very little back except a bit of gristle.

Cheese on toast

The combination of grain and dairy is so common that I’ve come to call some places “cheese on toast restaurants”, for aside from the shape of the food, that’s all they serve. Pizza, lasagne, cheese sandwiches, quiche and cheesecake are all fundamentally the same food. Since starting to eat paleo, I’ve introduced many new things into my diet I didn’t eat before, for example: spinach, olives, sardines, avocado, pecan nuts and redcurrants. These are all different foods, and so it’s ironic that since apparently restricting the foods I eat (by about 5 things), I eat a much greater variety than I used to.


Legumes range from soy beans, castor beans and kidney beans to lentils, chickpeas, peas and runner beans, but the group also include peanuts (a fact not as widely known as it should be).

Castor beans are the source of ricin: a handful of raw beans will kill a human.

Soy beans are also toxic raw, which is why I find it somewhat ironic that the Wikipedia page for the subject has a section titled “Health benefits”. Soy has an oestrogen-mimicking effect: drinking soy “milk” is like drinking contraceptive pills, a fact apparently lost on the stream of health-conscious women I see ordering soy lattes in Starbucks. Mercifully, I haven’t yet heard of any parents feeding a soy “milk” to an infant, but I daren’t Google anything along those lines. Phyto-oestrogens (plant oestrogens) are also harmful to males, as they disrupt the normal hormone balance even more.

I’m very fond of Chinese food (which is very easily adapted to paleo eating), and many dishes are made with soy sauce. However, it’s in small enough quantities that I make an exception here. Beancurd (aka tofu), is something I steer wide clear of. This has been one of my guiding principles to make eating paleo practical, I’ll eat “contaminated” food (eg a sauce thickened with a small amount of flour), but not a food made substantially from a non-paleo food, eg bread. How far you can get away with this depends on your tolerance to certain foods.

The prevalence of peanut allergy compared to other “nut” allergies is entirely in line with what the paleo theory predicts.


I don’t have a strong opinion on potatoes compared to some paleo eaters. They’re the root of a nightshade plant, and related to tomatoes, peppers, aubergines, chillis (and tobacco). Some hardcore paleo eaters avoid all these as they fail the “New World” test: they were imported from the Americas a few hundred years ago, and are therefore technically more recent introductions to the western diet than grains and milk.

Nightshade plants, include potatoes, include toxins called glycoalkaloids. Wild potatoes are dangerous to humans, but they’ve been bred to be safer. On this basis, and the observation that they are not as widely allergenic as many other non-paleo foods (although by no means not a health risk), I tend to consider them a low-quality food rather than something to strictly avoid. The mistake I see with potatoes is that people treat them as a staple rather than as any other vegetable: I’ve never seen anyone eat, say, turnips in the same dietary proportion as most people eat potato.

Hunter-gatherer diets often include poor-quality or even poisonous plants if they can be prepared to be safe enough to eat, but these are foods of a last resort. The anomaly in the west is that we’ve taken starvation foods and made them 75% of our diet.

Vegetable oils

This is something off most people’s radars, yet it’s actually an important topic. Over the last few decades there has been a shift from cooking with natural animal fats to mechanically and chemically processed vegetable oils. These are no more a part of the human diet than grains or cow’s milk.

There’s a misconception that saturated animal fats are bad for you (they “clog your arteries”, allegedly), and unsaturated vegetable oils are good for you (they “lower your colesterol”, if you believe the Flora marketing spiel). This is a huge topic, and possibly the most contested point in medicine today. If you want an authoritative opinion, see the work of the medical professionals who joined The International Network of Cholesterol Skeptics. Don’t think of animal fats as thick, artery-clogging materials: at body temperature they are liquid. But do think what happens to vegetable oil around the neck of a bottle: as it oxidises, it goes hard and rigid (which is why linseed oil makes good varnish).

The fat/cholesterol-heart-diseases hypothesis makes no sense according to paleo theory. Meat is a natural part of the human diet, and fat is the predominant source of energy in meat. The clearest counterexample is the Inuit people of the arctic circle, who were discovered in the 19th and early 20th century to be completely absent of heart disease and cancer, despite living on a diet of almost pure meat. The most famous explorer to study them was Vilhjalmur Stefansson, who subsequently ate a diet of pure meat for a whole year under medical supervision, to prove that it is possible.

I can corroborate Vilhjalmur Stefansson’s experience. In August 2010, as an experiment, I ate nothing but meat for the whole month. It is perfectly sustainable, and the only downside is it can get boring after a while (in part due to the lack of sudden, spectacular death or other side-effects that most people predict). On the plus side, after a couple of weeks to adjust, I had by far the best digestion I’ve ever had – my stomach has never been happier. Nowadays I rarely eat a diet of pure meat for prolonged periods, but I happily go several days in a row eating only meat when I’m travelling, as I find it convenient. I don’t actively recommend this to others, but it suits me fine.

Fat and carbohydrate

Many people, when I tell them that I don’t eat grains and potatoes, draw the false conclusion that paleo is a “low carb” diet. The naked-with-a-sharp-stick-and-a-big-stone(-and-maybe-a-fire) test says nothing about the carbohydrate content, fat content, or even the shape or colour of the food. But paleo diets tend to be relatively lower-carb than western diets simply because of the physical impracticality of eating typical western carb-levels on a diet of meat, fruit and veg.

This incidental reduction in carbohydrate leads, however, to a very important fact: it is vital on a paleo diet to eat enough fat. The human body can only extract so much energy from protein; we’re not designed to live off lean meat. Attempting to do so leads to what the american colonialists named “rabbit starvation”: death from starvation even despite eating huge quantities of lean meat. Unfortunately, the fat aversion we’ve been indoctrinated with makes it psychologically difficult for many people to go from a diet of trimmed steak and skinless chicken breast to untrimmed belly pork and duck.

The other important point to remember when reducing carbohydrate intake is that if you’ve lived your entire life predominantly off carbohydrate, your fat metabolism will be lazy. The first time involves a few unpleasant days of headaches at best, and it can take many weeks for some people to acclimatise to living off fat. After that, it’s easy to switch from burning fat to carbohydrate. Humans run much smoothly off fat, as we carry a plentiful supply. We store relatively little carbohydrate, and our bodies prefer to conserve it for intense exercise.

I remember quite early on being faced with the contradiction that logically, it must have been safe for the Inuit to survive off a diet of animal fat, yet I’d been scared into believing that animal fat was bad for me. Eventually I chose the logical consistency and documented evidence of the former over the contested commercial interests of the latter, and have never once since been concerned about the consequences of the amount of animal fat I eat.

Life expectancy

A common question I hear goes something like “didn’t cavemen lead short, brutish lives?”. There are two separate concepts here: quantity of life, and quality of life. All domesticated animals have longer life expectancies than wild ones, simply being safer from injury and death from predators, accidents, competition and starvation. Also, life expectancy figures include infant deaths, the most common age of death in the wild (and in civilisation, until recently).

The concern of a paleo diet is not life expectancy, but quality. In fact, the effect of civilisation to increase life expectancy has only exaggerated the detrimental effects of an agricultural diet. People weakened from diabetes, cancer, heart disease, dementia, and uncountable other diseases of civilisation, suffer far longer than anyone in a hunter-gatherer society would have, from disease that did not used to exist, and not merely because they “didn’t live long enough”.

There is no reason to believe someone living on a paleolithic diet today would not achieve the same or longer life expectancy than someone on a western diet, but they would do so with a far better quality of life. A good example is in Michael Eade’s comparison of Jack LaLanne vs Ancel Keys. Jack LaLanne was warning about the dangers of sugar, and our population of Sugarholics back in the 1950s; Ancel Keys was the original vocal proponent of the idea that animal fat and cholesterol causes heart disease. Look how they both ended up.

What does a paleo diet look like?

Basically, take everything you see in a western diet, subtract the things I’ve listed above as being non-paleo, and you have a paleo diet. Paleo is exclusionary, not inclusionary. There are no “paleo supplements”, no foods that weren’t otherwise eaten.

My own diet is basically meat and vegetables. I eat some fruit, but not a lot, and some nuts, but again, not a lot. I go for fatty meat over lean meat, for reasons explained above, and I’m especially fond of belly pork. Most of my meals look like a Sunday roast dinner. It’s generally only when I refuse something such as cake or ice cream than anyone asks me any questions.

I eat less frequently than most people, generally only eating in the evening, with a light snack (eg a piece of fruit) at most during the day. To some, this is a form of intermittent fasting, a subject I’ve largely glossed over here. I’ve found my appetite sufficiently reduced eating a paleo diet that I don’t need to eat more often. Initially I suffered from the indoctrinated fear that if I didn’t eat three times a day, and certainly, if I didn’t eat every day, I’d drop dead from weakness. Fortunately, common paleo sense is in line with reality here, and there are no such deadly consequences.


Most of the exercise I’ve done has been weightlifting for strength training. I eat relatively little carbohydrate, sometimes none, which has baffled people I’ve trained with in the gym, as they assume I should have no energy. I never eat before training, which led one person to wonder why I don’t just collapse during a workout.

I’ve also trained on a more extensive intermittent fasting schedule, eating only in an 8 hour window every two days (ie, 40 hours fasting, 8 hours eating). I’ve regularly trained twice in one of these cycles period, ie at some point lifting weighs after over 24 hours of not eating. And I’ve done all this while gaining around 1kg of muscle per month. All of this should put to rest any nonsense about needing to “carb up” for anything but the most extreme endurance exercise. I have no interest in being an Ironman contestant.

As with the times I eat zero carbohydrate (when I’m eating only meat), intermittent fasting is not something I active recommend to people. But it’s possible, and it completely disproves many of the false claims about what a “healthy” diet must look like.

Further reading

There are some excellent books on paleo and some not so. These are the ones I recommend. The only one I don’t recommend is Loren Cordain’s The Paleo Diet, solely on the basis of the absurd recommendation to eat lean meat. This is something I know from personal experience to be wrong, and it’s such a fundamental mistake I refer people to more consistent authors. This is not to dismiss Cordain’s otherwise extensive knowledge of the subject, but I can’t recommend this one book.

The simplest introduction is Ray Audette’s Neanderthin. It’s very much a layman’s book, which is why I like it. It also contains a lot of recipes, if you like that sort of thing. It’s an excellent starting point.

An excellent hidden treasure is Richard Mackarnass’s Not All in the Mind, written by a doctor practising mainly in the 1970s. I first found a copy of this for 60p in a second-hand bookshop on the Isle of Wight. It’s a more technical, but still accessible book, nominally about “food allergy and mental health”. The diet he prescribes is almost entirely paleo. The story I find most memorable was a woman who’s schizophrenia was cured, and, through excruciatingly stringent blind trials, demonstrated to be caused by food (including potatoes in this case).

The most thorough book I’ve read, and it’s almost encyclopaedic in nature, is Barry Groves' Trick and Treat. This book is the result of some twenty years of painstaking research into “healthy eating”, and is meticulously well-referenced. It’s hard work to read cover-to-cover, simply due to its length, but it’s worth having a copy just to be able to look up specific topics.

I’ll end with a mention of Gary Taubes' The Diet Delusion. I own a copy of this, but due to its size have not got round to reading it. It’s highly regarded in paleo circles though, so I’ve listed it to avoid looking like I was avoiding it like Cordain’s The Paleo Diet. It’s certainly one I’m keeping on my shelf.


I’ve eaten a paleo diet happily for nearly 8 years now, starting in early 2004. I haven’t fully recovered from the effects of the milk intolerance I suffered, but my health is in a different league now to what it used to be. I’m almost completely withdrawn from the addictive, harmful foods that make up the majority of most western diets. I have absolutely no desire to eat cakes, biscuits, cheese, pasta, pies or anything else of the sort.

I’m doing what many dieters believe impossible, so please be considerate enough to not interrupt me while I’m at it.

But if you have any questions, I’ll be happy to answer them in the comments.

5 responses
I have a question about your blog. Please email me!
Hi David

Sorry for the delay. If the question is not suitable for the comments for some reason, could you leave me an email address to contact you?


Great article Ash! But what about alcohol -- surely fermentation is yeast farming, and therefore non-paleo?
Hi Kevin

Fermentation is actually a perfectly natural process, and many animals get drunk near the end of fruit seasons. For example: "Sozzled elks hound old folks home[1]". Monkeys and elephants are just as fond of fermented fruit.

So whether alcohol is paleo or not depends on what it's made from. This means fruit-based alcohol (eg wine, cider, perry) is broadly paleo, but grain-based alcohol (eg beer, whisky) is not. Other factors that make alcohol less paleo include the addition of sugar and artificial preservatives, or indeed anything else that would not otherwise be considered paleo.

There's also a quantity issue: in most parts of the world, alcohol is only available in late summer, so we can't make any assumptions about how much our bodies can process safely over a prolonged period.

As an interesting aside, there's reason to believe that alcoholic liver cirrhosis can only form in the presence of unsaturated vegetable oil, and that saturated fat protects against it[2,3,4]. Those are not human studies though. I believe there is more about this in Barry Groves' Trick and Treat[5], but I won't have my copy to hand until tomorrow.

Hope that all clears this one up, at least a bit.


[1]: http://news.bbc.co.uk/1/hi/world/europe/4419876.stm
[2]: http://www.ncbi.nlm.nih.gov/pubmed/16108051?dopt=AbstractPlus
[3]: http://www.ncbi.nlm.nih.gov/pubmed/15051845?dopt=AbstractPlus
[4]: http://www.sciencedirect.com/science/article/pii/0024320594004048
[5]: http://www.amazon.co.uk/Trick-Treat-Healthy-Eating-Making/dp/1905140223/

If animal fats are liquid at body temperature, why doesn't my fat slosh around inside me right now...?