Paleo vs. Keto Diet: Similarities, Differences And Research

The United States has a weight problem.

In 1999, 30% of American adults were obese. By the late 2010s, the number had jumped to 42%, and the number of people with what the Centers for Disease Control calls “severe obesity” had doubled. (1) One report published in the British medical journal The Lancet predicts that 50% of American adults will be obese by the year 2030. (2)

Since obesity is known to be a major risk factor for many serious illnesses and diseases like type 2 diabetes, heart disease, stroke and cancer, the continuing increase in obesity is a grave concern for health professionals – and for the many people who badly need to lose weight.

That concern has driven interest in dieting to an all-time high in America. And two of the most popular diets over the last few years have been the keto diet and the paleo diet (sometimes called the “caveman diet”).

Both diets focus on high-quality, healthy foods. Both also promise quick weight loss, achieved primarily by dramatically reducing carb intake while boosting the amount of fat in meals.

But there are key differences between the keto and paleo diets, and research shows that one may be better for your overall health than the other.

What are the differences between the two diet plans, and which one should you choose? Before considering paleo vs. keto, we need to look a little more closely at each diet.

What is the Paleo Diet?

Modern paleo eating plans were first developed in the 1970s, and rapidly gained popularity some 30 years later when the fitness company CrossFit embraced the concept. However, the “real” paleo diet is about 10,000 years old.

In essence, paleo is based on the diet our ancestors ate back in the Paleolithic era.

Naturally, cavemen didn’t have today’s refrigerators, cooking equipment and food processing capabilities, so their ability to prepare and store food was quite limited. But the key elements of paleo eating go much further than that.

Early humans were hunter-gatherers. Their diets consisted primarily of protein and fat from the animals they were able to kill, and carbohydrates from the vegetables and fruits they were able to gather. They lived – and prospered – on whole foods providing lots of protein, fat, cholesterol and fiber, without the dairy products, grains and refined carbohydrates, farmed proteins and sodium prevalent in today’s diets. They also, by necessity, got much more exercise than humans do today.

Those facts, combined with something called the “evolutionary discordance hypothesis,” led to the concept of the modern paleo diet. (3)

Proponents believe the human body evolved to be able to thrive on the moderate-protein, high-fat, low-carb diets eaten by hunter-gatherers. (Vegetables and fruits do contain carbs, but in very small levels compared to the processed foods we eat now.) Proponents also believe that mankind has seen an enormous increase in obesity, illness and chronic disease because our we have become reliant on foods very different than what humans were “meant” to eat. 

Bottom line: the low-carbohydrate, high-fat paleo diet is based on a general medical and lifestyle philosophy (“they were healthier than us, so we should eat what they ate”), not rigorous biology and science. As you’ll read next, that’s quite different than the theory behind the keto diet.

What is the Keto Diet?

The ketogenic diet doesn’t have the same “history” as the paleo diet. It was first used in the 1920s as a treatment for stubborn cases of childhood epilepsy, and abandoned when more effective medical treatments were discovered. It made a comeback in the 21st century as a popular weight loss regimen. (4)

The early version of the keto diet was designed to mimic the biological effects of fasting, which had been used for centuries to effectively treat epilepsy. Keto eating plans were obviously not as drastic as fasting, but had the same effect: forcing the body to enter a metabolic state known as ketosis. Here’s why that’s important.

In the body’s normal state, dietary carbohydrates are turned into glucose (or blood sugar), which is the body’s primary energy source. When carbs aren’t available, though, the body enters the metabolic state known as ketosis, so it can generate molecules called ketone bodies (ketones for short) as an alternate source of energy.

What does that have to do with dieting? In a nutshell, ketones are produced when the body burns stored fat. So if you deprive the body of carbs, you force it to consume its fat stores in order to produce ketones. And burning stored fat is the fastest way to achieve significant weight loss.

The keto diet is not just a low-carb, moderate-protein, high-fat diet. It specifies optimal amounts of calories to be consumed from each macronutrient type. The recommended mix of approximately 5% carbohydrates, 20% protein and 75% fat has been found to put the body into a state of ketosis, usually within a week and often sooner. That’s when fat burning begins in earnest.

In summary, ketogenic eating is based on biology and science, rather than the paleo diet’s philosophical belief that our bodies were designed to eat just like our ancestors did.

Paleo vs. Keto: Which Works Better for Weight Loss?

Research on the effectiveness of each diet is limited. However, there’s some evidence showing indications that they each can help with weight loss.

Studies focusing on the paleo diet have involved very small groups of participants. But the results all show either weight loss of 5-10 pounds over a relatively short period of time, and/or significant decreases in important metabolic metrics related to weight and heart health like cholesterol, triglycerides and blood sugar levels. (6)(7)(8)(9)(10)

More expansive research has been done on the keto diet. It’s been shown to produce significant reductions in body weight and body mass, and lowered glucose, cholesterol and triglyceride levels. (11)(12) It was even able to reverse type 2 diabetes in some cases. (13) Some of the weight loss may be due to keto’s ability to reduce the appetite (14) and cause the loss of water weight. (15) But there’s little doubt that a ketogenic diet is effective over the short term. (16)

Research has shown that low-carb diets are better than low-fat diets for weight loss. (17) Unfortunately, there has been no rigorous scientific comparison between keto and paleo. That makes it impossible to definitively say that one is better than the other.

However, the characteristics of each diet may help you choose between the two.

Paleo vs. Keto: Pros and Cons

The paleo and keto diets each greatly restrict what you’re supposed to eat, making the diets a challenge and willpower a must. Beyond that, though, there are pros and cons (other than the obvious benefit of weight loss) to each eating plan.

Paleo Diet

Pros:

Cons:

Keto Diet

Pros:

Cons:

Each diet has only been studied for its short-term effects; there is no research showing that either keto or paleo is safe as a long-term dietary approach.

Finally, people with existing medical conditions may be affected negatively by the paleo and keto diets, and should consult their doctor and a nutritionist before beginning either one.

Paleo vs Keto: What You Can and Can’t Eat

Even though the reasoning behind the paleo and keto diets is very different, what you can eat on the two low-carb diets is quite similar. 

Generally speaking, keto is higher in fat and lower in carbs than a paleo diet. But food choices for both diets are based largely on whole (rather than processed) foods, and they each eliminate many of the same food options.

The easiest way to compare the two is by food groups.

Proteins

There’s virtually no difference between the two diets when it comes to proteins; almost every type of meat, poultry, fish and seafood is acceptable. Fatty proteins are better than lean meats, and pastured, grass-fed meat, free-range poultry or wild-caught fish are preferable. They’re of higher quality and don’t contain GMOs, pesticides or other potentially toxic chemicals.

The only exceptions:

One other type of protein, eggs, gets the green light on both keto and paleo diets.

Carbs

Most of the carbohydrates (starches and grains) we eat regularly are off-limits on both diets. That includes bread, pasta and rice, and even whole grains. There are some fine lines, though.

Interestingly, both diets frown on legumes (like beans) but for different reasons. For keto, it’s because they’re too high in carbs. For paleo, it’s because cavemen didn’t have access to legumes.

Fats

The paleo and keto diets are mostly in alignment when it comes to fat intake. Healthy, unprocessed fats like olive oil, coconut oil and avocado oil are good, trans fats and processed oils like soybean and canola are bad (on most keto meal plans, that is). Paleo’s reasoning is simple: our ancestors didn’t have processed oils on their cave’s shelves. In keto, it’s more a matter of unprocessed fats being healthier.

The major exception here is butter (preferably grass-fed butter). It’s not allowed on paleo because cavemen didn’t eat it. (Some paleo eaters make an exception for ghee, although it’s hard to understand why.) But if there were keto ratings for foods, butter would get four stars as a food that’s carb-free and apparently not risky to heart health, as it was once thought to be. (31) The only issue is that it contains a lot of calories, so butter consumption should be balanced with the use of other oils.

Dairy

This one’s easy for most paleo dieters: our ancestors didn’t milk cows. They didn’t make dairy alternatives like nut butter or almond milk, either. Conclusion: no dairy. (Some paleo dieters do make an exception, though, for fermented dairy products sourced from grass-fed cows because they contains so many vitamins.)

We’ve already mentioned butter. Keto also encourages moderate consumption of full-fat, low-carb dairy products like cream cheese, sour cream, heavy cream, Greek yogurt and of course, cheeses that are relatively low in carbohydrates. (Most popular cheeses fit into the category.) The exception is milk, which isn’t keto-friendly because it contains high levels of a sugar called lactose. Unsweetened nut milks are fine, though. Low-fat dairy products? Sorry, they’re out.

So, Is Keto or Paleo the Winner?

There’s not enough research to tell for sure. They each lead to short-term weight loss, and each have advantages and disadvantages. Perhaps most importantly, there’s more scientific evidence on the benefits of ketosis and ketogenic eating – so it appears that the keto diet is the safer choice.

(1) https://www.cdc.gov/obesity/data/adult.html

(2) https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(11)60814-3/fulltext

(3) https://pubmed.ncbi.nlm.nih.gov/21139123/

(4) https://pubmed.ncbi.nlm.nih.gov/19049574/

(5) https://pubmed.ncbi.nlm.nih.gov/26268692/

(6) https://www.nature.com/articles/1602790

(7) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2724493/

(8) https://link.springer.com/article/10.1007%2Fs00125-007-0716-y

(9) https://onlinelibrary.wiley.com/doi/full/10.1111/joim.12048

(10) https://www.nature.com/articles/ejcn20094

(11) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2716748/

(12) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6520897/

(13) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1323303/

(14) https://pubmed.ncbi.nlm.nih.gov/25402637/

(15) https://pubmed.ncbi.nlm.nih.gov/27754807/

(16) https://pubmed.ncbi.nlm.nih.gov/17332207/

(17) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3530364/

(18) https://pubmed.ncbi.nlm.nih.gov/26269362/

(19) https://pubmed.ncbi.nlm.nih.gov/27235022/

(20) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356951/

(21) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4337919/

(22) https://link.springer.com/article/10.1007%2Fs00394-019-02036-y

(23) https://pubmed.ncbi.nlm.nih.gov/18700873/

(24) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1325029/

(25) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1334192/

(26) https://pubmed.ncbi.nlm.nih.gov/20687386/

(27) https://pubmed.ncbi.nlm.nih.gov/17313687/

(28) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112040/

(29) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451242/

(30) https://bmcnephrol.biomedcentral.com/articles/10.1186/s12882-016-0283-x

(31) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4927102/