The paleo diet, which mimics the diet of early humans, has much in common with a whole foods ketogenic diet. Both diets embrace vegetables, healthy fats, meat, and fish — and both forbid legumes, seed oils, refined sugar, and anything that comes in a package.
Both paleo and keto are compatible with good health, but they aren’t the same diet, and they don’t have the same health effects. Take weight loss. The question is: Which diet, paleo or keto, is more effective for weight loss?
Keep reading and find out what the science says.
The paleo (or paleolithic) diet hinges on a single principle: eat like your ancestors.
This doesn’t mean eating like your great grandparents. Rather, eating paleo means eating like ancient hunter-gatherers who roamed the Earth thousands of years ago.
These early humans evolved to flourish on certain foods: meat, fish, animal fat, berries, tubers, etc. Consuming these evolutionarily-preferred foods, paleo advocates believe, promotes optimal health. That’s paleo in a nutshell.
Paleo Diet Foods
There are many versions of the paleo diet, but below are the general guidelines.
On a paleo diet, you eat:
- Meat, fish, eggs, and organ meats
- Fresh fruits and veggies (as much as you like)
- Healthy fats like coconut oil, olive oil, avocados, butter, and palm oil
- Starchy roots and tubers
And you avoid:
- Industrial vegetable oils like soybean oil, safflower oil, etc.
- Grains (including whole grains)
- Anything processed
Probably because paleo bans grains, sugar, and beans — paleo diets are often low-carb. However, low-carb is the trend, not the rule of paleo. Since vegetables (including starchy veggies) are allowed, paleo ranges from low to high-carb, and everywhere in between.
You might be wondering: Why are legumes and dairy prohibited on paleo? Aren’t those ancestral foods?
Depends who you ask. Legumes, for instance, contain high levels anti-nutrients (lectins and phytates) that damage the gut and inhibit nutrient absorption from food[*]. Ancient cultures, however, would sprout and soak legumes before serving them, removing most of the harmful compounds in the process.
The paleo argument against dairy is less clear. The claim is that hunter-gatherers didn’t drink milk, so neither should we. But here’s the thing. Many people, especially those of Northern European descent, have evolved to tolerate dairy. These folks have more lactase, a special enzyme that digests milk sugar[*].
Not all paleo sources shirk dairy though. For those who can tolerate it, dairy is full of healthy nutrients, and not necessarily counter to human evolution.
The bottom line? For better or worse, a strict paleo diet means eating exactly like ancient homo sapiens ate.
Like the paleo diet, the ketogenic diet lacks sugar, grains, legumes, and industrial seeds oils. Unlike paleo, however, the goal of keto is to promote a unique metabolic state called ketosis.
Here’s how that works. When you eat a very low-carb, very high-fat diet (the keto diet), your blood sugar and insulin levels stay low. This tells your body: hey, carbs are scarce, time to burn fat and make ketones!
Ketones are special molecules, made in your liver, that can easily, cleanly, and efficiently convert to energy, or ATP. This energy goes on to power every cell in your body, including your neurons (brain cells)[*].
Once you’re fat-adapted (after four to six weeks of keto dieting), you start burning fat instead of glucose to power your body. This leads to fat loss, reduced cravings, lower inflammation, clearer cognition, and more stable energy[*][*][*]. These health benefits have made the keto diet extremely popular, but it’s not how keto got started.
The Original Purpose of Keto
The ketogenic diet was not created for weight loss, body composition, blood sugar, or any other such benefit. Rather, keto was created for a specific medical condition: epilepsy.
Take a little trip back to the 1920s[*]. Researchers had just discovered that fasting had antiseizure properties, and they thought: if fasting works so well for seizures, why not create a fasting-mimicking diet for children with incurable epilepsy?
Keto was that fasting-mimicking diet. Keto is high-fat because, on a fast: you burn fat to fuel your energy needs. In other words, a fast is a high-fat diet.
Back to the science now. Among epileptic children, a ketogenic diet reduced not only the frequency, but also the intensity of their seizures. The more ketones a child produced, the fewer seizures that child had. Later, the keto diet was also found to be effective for adult epilepsy[*].
The ketogenic diet has also been shown, in study after study, to be an effective diet for weight loss. What about paleo? Keep reading.
If your goal is weight loss, which diet is better: keto or paleo? It’s not a super-complicated question. The science should answer it.
Keto for Weight Loss
The ketogenic diet is all about macronutrient ratios. On keto, you eat about 60% fat, 30% protein, and 10% carbs by calories. You can give or take on fat or protein a bit, but carbs must stay under 10% to enter the ketone-zone.
The main benefit of keto is metabolic. Less carbs, less blood sugar, less insulin, more fat burned, more weight lost. Pretty straightforward.
In addition to the metabolic benefit, ketosis also affects hormones relevant to weight loss. For instance, a keto diet has been shown to lower circulating levels of ghrelin — your hunger hormone[*]. Less ghrelin, less cravings.
Keto is like a double-edged sword for weight loss. On one edge, you burn more fat. On the other, you crave (and eat) less food.
Add to these mechanisms the thousands of people reporting weight loss on keto, and you have a fairly compelling argument. But to be totally sure, what does the clinical evidence say? Here are some published examples:
- In healthy women, a keto diet caused more weight loss over six months than a calorie-restricted low-fat diet[*]. (You read correctly — keto beat out calorie restriction for weight loss!).
- Adolescents lost more weight on a low-carb diet than on a low-fat diet[*]
- In obese people, 24 weeks of keto dieting significantly improved body composition[*]
- In 164 adults, a low-carb diet improved energy burn during weight loss maintenance[*]
There are many more examples, but you get the picture: the ketogenic diet is a proven weight loss diet.
So. What about paleo?
Paleo for Weight Loss
Unfortunately, the research on paleo for weight loss is a bit thin. The evidence is more theoretical or anecdotal, and you don’t have stacks of science (as with keto) showing significant weight loss in controlled, clinical settings.
Nonetheless many folks have reported successful weight loss on the paleo diet. Here are some potential reasons why:
#1 Calorie Restriction
Some researchers believe people lose weight on the paleo diet, not because ancestral dieting has special metabolic effects, but because on paleo, people eat fewer calories[*].
This is also true of intermittent fasting (IF). IF means eating within an 4-12 hour window every day, and not eating (fasting) for the remaining hours. IF could also mean doing 24-hour fasts every other day, once a week, or once a month.
Many paleo folks practice intermittent fasting, which could explain the total decrease in calories on the paleo diet. Less food in, less weight gained.
#2 Metabolic Benefits
Several studies have shown that a paleo diet improves blood sugar and cardiovascular risk factors in those with type 2 diabetes[*]. This isn’t surprising, considering the standard diabetes diet is high-carb, and less focused on protein and fat than paleo. Researchers suspect it’s the high-protein intakes on paleo that may improve obese or diabetic metabolisms[*].
But when you look at the bulk of the science, it’s not high-protein diets per se, but very low-carb ketogenic diets that have proven most effective for treating and reversing type 2 diabetes. There’s no shortage of high-quality controlled trials supporting this point[*][*].
Which makes you wonder: since paleo diets are often low-carb, could this explain weight loss on paleo?
#3 Paleo and Low-Carb
Since the paleo diet prohibits grains and sugars, many paleo folks find themselves slipping into low-carb dieting. Tubers, roots, and other starchy vegetables are allowed — yes — but it’s harder to carb-binge on carrots than on, say, pasta.
Right. For reasons explained in the “Keto for Weight Loss” section, low-carb can be an effective strategy for reducing body fat. But there’s nuance here. It’s possible, in fact, to be low-carb, but not low-carb enough to start burning fat and producing ketones. In this case, your body will be in sugar-burn-mode, but there won’t be enough sugar around to burn.
This can be a problem. For instance, in the absence of ketones, your brain needs about 130 grams of sugar (glucose) per day to function[*]. And so if you’re eating 75 grams of carbs per day on paleo — that’s too high to get in ketosis, but perhaps too low to fuel your brain. This could cause brain fog, headaches, and cravings.
Bottom line? Depending on the situation, low-carb paleo diets may help with weight loss, but low-carb diets (that aren’t keto) may come with unwanted side effects.
Both paleo and keto are more or less restrictive. Depends on the dieter.
Dairy lovers will do better on the keto diet. Dairy fat was used to fuel the original ketogenic diet, and it’s chock-full of healthy nutrients. But for reasons that have little to do with science, dairy is typically forbidden on paleo.
Fruit and potato fans, on the other hand, may jive with paleo better. These foods have too many carbs for a standard ketogenic diet, but they’re perfectly okay by paleo lights.
If you really want to tighten the screws on your diet, you can combine paleo and keto. That means no fruits, no starchy veggies, no dairy, no grains, and of course, nothing refined. Maybe keep grass-fed or pasture-raised dairy products around if you can tolerate them.
There’s not much literature on the combined paleo-keto diet, but it has been shown, in a single case study, to successfully treat childhood epilepsy[*].
The verdict? Both paleo and keto have restrictions, so compliance depends on your tastes, goals, and personality.
If you find you’re adding pounds of fat mass on the paleo diet, here are some possible explanations:
#1 Too Many Carbs
Technically, you could eat mountains of sweet potato three meals a day and still be considered paleo. But what would all that sweet potato do to your metabolism? Well, high-carb (even high-carb paleo) diets can[*]:
- Raise your blood sugar levels (hyperglycemia)
- Raise your insulin levels (hyperinsulinemia)
- Increase cravings due to blood sugar spikes and crashes
- Put you in fat-storage mode (from high insulin) and promote weight gain
So yes, even healthy carbs can be unhealthy if you eat too many of them.
#2 Low-Carb, But Not Keto
Recall that low-carb diets are not necessarily keto. Many paleo dieters likely have carb intakes too low to fuel normal carbohydrate requirements, but too high to become ketogenic fat-burning machines.
This might, in theory, cause metabolic and hormonal issues that could interfere with weight loss efforts. It could also affect cognitive function, because your brain has high glucose needs when ketones aren’t around.
And the best evidence for weight loss on keto? In these studies, carbs were held under 10% of calories[*].
The lesson is: if you’re going to do low-carb, don’t do it halfway. Do it right.
#3 Eating Fat With Carbs
If you decided to write a book on the paleo diet, you might put a sweet potato on the cover. Inside that sweet potato — open, orange, steaming — would be sizable pat of butter. Definitely paleo-friendly.
But here’s the issue. Combining fat and carbs (simply adding butter to your potato) can make weight loss more difficult.
Why? Because this combo is hyperpalatable. Together, carbs and fat taste so good that all your sound dietary judgement flies out the window. Once you start, you can’t stop.
It’s true. In a very recent study, researchers showed that a mixed meal of fat + carbohydrate triggers reward circuits of the brain — circuits that govern eating habits[*]. Participants loved these mixed meals so much, in fact, that they were willing to shell out more money for them.
Eating carbs with fat also triggers a larger-than-normal insulin response[*]. Lots of insulin, unfortunately, means lots of fat storage.
The takeaway? Carbs and fat together are hyperpalatable, insulinogenic, and could lead to weight gain.
The Bottom Line: Which Diet Is Better For Weight Loss?
The fact is, there’s a lot to like about both the paleo and ketogenic diets. Both diets prohibit sugar, grains, legumes, and harmful vegetable oils and favor natural, whole foods. That’s over half the battle right there.
For weight loss, however, sometimes more is required than the removal of modern American industrial foods. Sometimes you need to jumpstart your metabolism.
While there’s evidence that the paleo diet can help with weight loss, there’s far more evidence supporting the ketogenic diet. And as you just learned, it’s possible that paleo could trigger weight gain, depending how the diet is formulated.
If the paleo diet is helping you lose weight, keep doing what you’re doing. If you’re struggling, however, hopefully this article has helped you understand why.