What is the evidence in favor of paleo?

I'm very skeptical of reasoning like "it was like that in ancestral environment so it must be good". There are at least three reasons that makes me uncomfortable with the reasoning :

1. Even if we consider evolution to be a perfect optimizer (which it is not), there is a huge difference between "our digestion system is optimized to make the best possible use of food X" and "food X is best possible food for our digestion system". If you made an algorithm A optimized to transmit data on a noisy channel N, it doesn't mean the algorithm wouldn't run better on a less noisy channel C. There may be an algorithm B that work better on the clear channel C than A, but still, A can work better on C than on N.

2. Evolution doesn't optimize for the same purpose we do. Evolution doesn't optimize for us to live long, it has a very low pressure to make us live past ~60, for example.

3. We have completely different lifestyles and activities than we did during paleolithic. And the optimal diet very likely depends of lifestyle and activities.

That said, what would convince me to do a diet is not a plausible-sounding reasoning, but some evidence of short-term and long-term effects on a sane sample size, with a control group. Something which seems very rare in the diet field, saddly.

From casual observation, paleo and intermittent fasting are the only diets that some people seem to like being on, as distinct from being burdens that some people think are worth the trouble.

I don't have anywhere near enough domain knowledge about the human body to (correctly) evaluate the arguments for and against particular diets, so I figured I'd just run an experiment and see what happened.

This is what happened.

I think part of the problem is that the question being asked varies. It matters what your aims are, (weight loss, general health, etc.) and what you're comparing it to. People tend to conflate:

• For aim X, is Paleo better than the generic unstructured diet I've had up to this point? Probably yes.

• For aim X, Is paleo better than a calorie and nutrient controlled diet based on all the available evidence? Probably not.

And what you mean by supporting it.

• Is the paleo 'philosophy' that you should eat like in the ancestral environment always going to be best? No.

• Is "eat more meat and vegetables and less refinied carbohydrates" a useful guideline for most people? Yes.

It looks as though some people are healthier if they eat some grains. One of my friends has even found that his digestion doesn't work well unless he eats a good bit of wheat. He hasn't experimented with other grains that include gluten. He's got a couple of relatives who show the same pattern.

I believe it's important to do your own experiments.

When I ask this question I am usually referred to Gary Taubes. Also see Wikipedia. I don't have time to evaluate the evidence, but I'm pretty skeptical of nutrition science in general.

Edit: Eliezer has spent a few years doing the only thing you can do: try a bunch of diets on yourself and measure the results.

A search through the NIH site does not seem to show a single reliable study on the subject...

The most obvious, and significant, argument in favor of paleo is that it tends to make it more difficult to overeat or maintain a lot of weight (i.e., it's acts as a fail-safe against akrasia). Imagine if you only had nuts, fruits, and vegetables to snack on and for anything else you had to cook a meal.

A better diet would be to push your eating window to 2-3pm to 10pm (intermittent fasting), and only eat low calorie things which you've cooked (and make sure you don't buy anything that can be eaten without being cooked).

Basically, from the research I've read, akrasia is the most significant factor in maintaining a healthy weight; anything you can do to force or impel your future self to commit to your non-akrasiac desires is a good idea.

I have a related diet question on portion size; I guess I'll ask here rather than the open thread or "stupid questions" thread. Is spreading out your carb intake over the course of the day as good as eating fewer carbs?

If the problem comes from glycemic load (spikes in blood sugar & insulin levels), then it seems like it should be. Instead of eating a big slice of pie in the afternoon, I could have half of the slice then and half at night. Or, even better, a bite of pie every 20 minutes. Then my body wouldn't be overwhelmed by a huge burst of pie all at once; the constant snacking would mimic the slow-release pattern of low glycemic index foods.

Hunter-gatherers eating traditional diets had very low rates of the modern "diseases of civilization" including cancer, heart disease and diabetes. When, however, hunter-gatherers switch to eating modern diets they start getting these diseases at high rates. (Of course this correlation doesn't prove causation, but still...) Also, anthropological evidence from bones show that populations usually became less healthy after adopting agriculture.

Although hunter-gatherers had lower life expediencies than we do, this was mostly due to them dying of stuff (murder, infections, viruses) that doesn't significantly reduce the life expectancy of Americans. The paleo lifestyle tries to combine the health virtues of modern day and paleolithic man.

I look at paleo as providing Bayesian priors for the health value of different foods. If food X was eaten for a million years by my ancestors whereas food Y was eaten for less than 20,000 years then my prior belief is that food X is probably healthier than food Y. This seems to be the implicit approach taken in the Perfect Health Diet. The value of paleo priors is inversely proportional to the strength of nutrition science.

Forgive me for not having citations to backup these arguments. They are based on my readings of the secondary paleo literature.

I switched from vegetarian to paleo based on Food and Western Disease, which had the best recommendations I could find at the time. I will take Dr. Linderberg's recommendations as what "paleo" means. Oversimplifying:

Yay: Lean meat, fish, veggies, root vegetables, fruit, some nuts. Drink water.

Boo: Grains, dairy, refined fats, sugar, beans.

The primary argument in favor of the 'yay' foods is nutrient density: you get a lot of micronutrients (and protein) per calorie. For instance, you want to consume about 100mg of calcium per MJ of energy you consume. Spinach has 1517mg calcium per MJ of energy. In general, vegetable have lots of micronutrients and not very many calories, so they have lots and lots of micronutrients per calorie.

There are two main arguments levied against 'boo' foods. First is that they tend to have low nutrient density. Bread (whole grain) only has 60mg of calcium per MJ of energy. Second, they contain antinutrients, ie. chemicals that bind to micronutrients so we can't absorb them. Phytic acid is an example of an antinutrient. Nuts also contain phytic acid, which is why you'll notice a recommendation against eating a lot of them.

The second approach is to copy examine.com's answer, which deals specifically with weight loss, as opposed to general healthy eating.

> Many diets, both fad and more long-term diets, do work. This is mainly because they reduce calories. > When people switch to a paleo-lithic (hunter-gatherer diet), the foods they switch to are naturally more filling (higher protein, fiber, water content) or have less calories for the size of the food eaten (due to water content; a pound of broccoli has less calories than a pound of grains). > When people switch to a ketosis diet (very low carb), the higher fat and protein levels naturally provide satiety and fill people up. Also, there is some evidence that obese people have a maladapted response to serotonin (of which carbohydrates aid in the synthesis of) and thus omitting carbohydrates omits cravings. People lose weight on a ketosis diet because they eat less on a day to day basis, and avoid large binges caused from carbohydrate cravings. > Diets that manipulate fasting (Intermittent Fasting, Alternate Day Fasting) may have some benefits on the 'calories out' side of things as prolonged fasting might increase heat expenditure, but the most significant means for weight loss here is that you control eating. It is much harder to overeat in 8 hours than it is in 16.

These are the arguments that have convinced me--first to do paleo, and then to completely abandon it and eat soylent. There's also evidence that when populations switched from ancestral to western diets, their health declined. I think this is interesting evidence, and gives us a reason to test ancestral diets. I'm not aware of enough sufficiently good testing to make particularly good arguments for any diet.

I eat paleo whenever I can't have soylent. This means "whatever Lindeberg said," (outlined above). This is not antagonistic to carbohydrates. In fact, Lindeberg's best know for studying the Kitavans, an ancestral population that gets 69% of its calories from carbs. If paleo means "whatever Lindeberg said," then I've presented the strongest arguments from his book. This set of foods tends to be high in nutrients, low in energy, and devoid of antinutrients, so we get the nutrition we want in not too many calories.

However, if "paleo" means "replace carbohydrates with protein/fat," I can't help you. I no longer frequent the paleosphere and don't care which definitions you map to which diets. I've presented you with the strongest arguments I know for the diet I associate with "paleo". Sorry if that's not the diet you were looking for.

If paleo/primal advocates were strong rationalists, they would state the basic premise of the diet as follows:

"In the absence of evidence, the safest bet is to go with an ancestral diet."

And I think it is difficult to argue with that. When the evidence is mixed on a topic, it seems natural to default to tradition. In general I think paleo/primal dieters consider non-ancestral foods guilty until proven innocent...as in, you would have to present them evidence that a non-ancestral food was harmless and healthy before they started eating it. Most people are asking "Why shouldn't I eat X", but within the paleo/primal philosophy, the burden of proof rests on the advocates of novel foods, since they are the one who deviate from the ancestral default. If you want to debate what exactly the ancestral default was, that is an entirely different can of worms...but it is easy to say which foods are certainly not ancestral.

By the way, carbohydrates are not criticized by the paleo movement. You're thinking of Atkins. Fruits and tubers were part of our ancestral diet, and they are rich carbohydrate sources. They are encouraged in moderation.

The paleo criticism is that the modern diet's primary source of calories is now grain, which was scarce in the ancestral environment. More dedicated paleo folks will also attack milk, legumes, and nightshade vegetables (in that order) but really the majority of complaints are directed at grain. Before agriculture, no one really ever ate it. After agriculture, the population boomed and people didn't really have any better options other than grain. Now grain has been ingrained into our culture (pun intended) even though we have the resources to avoid it.

Anyway, there are three compelling pieces of evidence against grain: Lectin, Gluten, and Phytic Acid

1) Grain contains large amounts of phytic acid. Nuts contain more than wheat, but we don't typically eat that many nuts per day. Chemists would call it a chelator, something that binds with ions. Dietitians would call it an anti-nutrient...it essentially stops your body from absorbing Zn, Fe, Ca, and Mg. Ruminants and grain-eating animals have evolved mechanisms to break it down, but humans have not.

2) Lectin is a natural pesticide which irritates gut linings. Over time, it causes leptin resistance...which contributes to unhealthy fat storage patterns and other metabolic disorders like diabetes.

3) While the gluten free craze is a bit out of hand, there is increasing evidence for a gluten sensitivity spectrum. Not everyone is a celiac, but a substantial proportion of the population experiences some amount of gut inflammation via gluten.

Add to these three things the notion that grains make it easy to consume large numbers of calories and can cause sudden spikes in insulin, and I think you have a pretty good idea of why the paleo/primal diet discourages extensive grain consumption. It's really more about toxin and anti-nutrient avoidance than it is about carbohydrate vs fat as a calorie source - although it is generally agreed in these circles that modern diets are a bit carb heavy.

Here are some reasons why people might be better off eating less carbohydrates & more fat or protein:

*http://www.ncbi.nlm.nih.gov/pubmed/15148063

Compared with a low-fat diet, a low-carbohydrate diet program had better participant retention and greater weight loss. During active weight loss, serum triglyceride levels decreased more and high-density lipoprotein cholesterol level increased more with the low-carbohydrate diet than with the low-fat diet.

In addition, the low-carbohydrate group lost less lean body mass:

Patients in both groups lost substantially more fat mass (change, -9.4 kg with the low-carbohydrate diet vs. -4.8 kg with the low-fat diet) than fat-free mass (change, -3.3 kg vs. -2.4 kg, respectively).

*http://www.ncbi.nlm.nih.gov/pubmed/18635428

Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets. The more favorable effects on lipids (with the low-carbohydrate diet) and on glycemic control (with the Mediterranean diet) suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions.

The patients on the low-carb diet lost more weight & better improved HDL:

The mean weight loss was 2.9 kg for the low-fat group, 4.4 kg for the Mediterranean-diet group, and 4.7 kg for the low-carbohydrate group (P<0.001 for the interaction between diet group and time); among the 272 participants who completed the intervention, the mean weight losses were 3.3 kg, 4.6 kg, and 5.5 kg, respectively. The relative reduction in the ratio of total cholesterol to high-density lipoprotein cholesterol was 20% in the low-carbohydrate group and 12% in the low-fat group (P=0.01).

*http://www.ncbi.nlm.nih.gov/pubmed/20679559

CONCLUSION: Successful weight loss can be achieved with either a low-fat or low-carbohydrate diet when coupled with behavioral treatment. A low-carbohydrate diet is associated with favorable changes in cardiovascular disease risk factors at 2 years.

They also saw greater improvement in HDL ("good") cholesterol in the low-carb group:

Increases in HDL cholesterol levels were significantly greater in the low-carbohydrate than in the low-fat group at 3, 6, 12 and 24 months.

They also mention another reason that LDL increases in the low-carb group may not increase cardiovascular risk:

[...]assessment of LDL cholesterol concentration without information on LDL particle size has limitations as an indicator of coronary heart disease risk because small, dense LDL particles are more atherogenic than large LDL particles (24). Data from carefully controlled studies demonstrated that isocaloric replacement of dietary carbohydrate with fat increases plasma LDL cholesterol concentration but shifts LDL particle size from smaller to larger and less atherogenic LDL (25).

*http://www.ncbi.nlm.nih.gov/pubmed/12761365

CONCLUSIONS: The low-carbohydrate diet produced a greater weight loss (absolute difference, approximately 4 percent) than did the conventional diet for the first six months, but the differences were not significant at one year. The low-carbohydrate diet was associated with a greater improvement in some risk factors for coronary heart disease.

Again, the low-carb diet better increased HDL: +18.2 for the low-carb group, +3.1 for the conventional group (P=0.04).

It also better decreased Triglycerides: -28.1 for the low-carb group, +1.4 for the conventional group (P=0.04).

Note: This is a copy of a comment I posted months ago in another diet thread.

We may soon be getting some real data. From Gary Taubes' blog: http://garytaubes.com/2012/01/updates-for-2012/

"Among the projects we have in the works is a non-profit, the Nutrition Science Initiative (NuSI), to raise money for the kind of research we think is necessary to clarify the relationship between dietary nutrients, obesity. diabetes and their related chronic diseases. We have a specific plan of research to pursue (or rather to fund so that established, unbiased researchers can then do the studies) and have already recruited a world class scientific advisory board and executive board."

According to a later post: "We’ll say much more about this when we formally and publicly launch NuSI in early September. The ultimate goal is to create what would ideally become a kind of Manhattan Project of Nutrition: a concerted, directed, well-funded research effort composed of the best scientists in the field — all independent and suitably skeptical — working together to generate the evidence necessary to put to rest, one way or the other, all the major and many of the minor controversies in nutrition research."

Many of the diets that appear to "work" (meaning reducing fat and supporting lean muscle mass) restrict carbohydrates, especially forms of carbohydrates that are rapidly metabolized. In my view, this commonality is much more interesting than the theoretical arguments for one diet versus another.

Anecdata: I have lost over 30 pounds since switching to a vaguely paleo (but really more carb avoiding) styles of eating last december. I track my weight daily, and cheat on saturdays, except a couple weeks ago when I cheated for the whole of Gencon. Very reliably, I gain weight after Saturdays, and gained 9 pounds over the course of Gencon. I tend to lose weight after days that I do not eat carbs on, and my lowest weight for a given week is almost always on Saturday morning. I do not track calories at all.

Anecdotal: the weight lifters / body builders I know say less carbs and more protein is helpful to their goals, and they say that paleo and/or Atkins is something to cycle through and not adopt as a lifetime diet. Three months of less carbs and more protein, three months of something else, three months of etc.,then if needed or desired three months back to less carbs and more protein. That time limit is something I see lacking in most discussions on the topic, and if I hadn't been told directly I wouldn't have known either.

Anecdotal: met a guy once who said he'd lost a large amount of fat quickly and kept it off using Atkins. He had adopted it as a lifetime diet.

Anecdotal: if I eat somewhat less bready stuff, I've got more pep in my step.

These anecdotal facts are large-percentage true and small-percentage applicable to anyone else. Look ma, I'm learning to speak Bayesian!

Modern highly processed food is optimized to our sense of taste, to the extent that they can be called superstimuli. They are also correspondingly unhealthier, on many metrics. (I suppose this is the part in contention... I don't have any sources for this claim, sorry.)

The paleo diet, as well as the Atkins diet and other diets, inadvertently 'works' because highly processed foods tend to be carb-based (crackers, cookies, chips, sugary cereals, sugary yogurts, sugary soft drinks, sugary baked goods), and are thus excluded.

Right of the top of my head. Not all of them are scientific rigorous, just evidence that points against carbs.

• A high carb diet was only introduced around 10k years ago with the invention of agriculture. As hunter/gatherers the diet was mostly hunted animals(protein/fat) and some occasional carbs from gathered fruits. So the human body is mostly adapted to protein/fat.

• Methabolic pathways. Carbs once inside the body are broken down into sugar, which hasn't much nutritional value other than providing energy and the excess is converted into fat. Proteins can be used to make energy too, but obviously are much more nutritious. Fat and protein is digested with a different methabolic pathway that will also assist in burning body fat. But all fat burning stops once you ingested carbs and the blood sugar raises which makes it hard to lose body fat. There is evidence that your muscles can also function more efficiently in fat burning mode, but for this transition to occur you have to get rid of all the carbs first(including the glycogen stored in your muscles) and retrain your metabolism(may take weeks).

• you can survive on a diet without carbs but you can't survive without proteins and fat(there are essential fats that are needed by the body).

• Certain kinds of problems can be solved by a low carb diet(at least one kind of epilepsy), suggesting that certain adaptations are recent.

• Lots of people develop health problems(overweight, diabetes) that has to do with an excess of carbs. Also there is a general trend in these problems over the years as people are consuming more and more high carb diet(aka junk food).

• Carbs are appetite stimulants, causing overeating.

• It's easy to overeat in carb in general, they literally just melt inside your mouth, whereas with meat you have to do real work(chewing and digesting). Try eating just meat/fat for one week, I found this to be almost impossible.

From my personal experience it is very hard to keep a low carb diet because carbs are just so delicious, try staying off them for just one week and you will understand.

Just one link that I found right now: 60 Minutes explains the latest science behind the conclusion that excess sugar has measurable toxicity, the liver creates fats from excess sugar then linked to blood clots and heart disease, and cancer rates are linked to excess sugar, and reward regions make can sugar addictive