When it comes to paleo vs. keto, you may be wondering which one will help you lose the most weight while staying healthy.
Paleo (short for the “paleolithic era”) mimics the diet of early humans, and it 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 processed food.
Both paleo and keto are compatible with good health, but they aren’t the same diet. They don’t have the same health effects or requirements. Depending on how you practice each one, they could have dramatically different outcomes when it comes to healthy 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 — it means eating more like cavemen, in a hunter-gatherer sort of way.
These early humans evolved to flourish on certain foods: meat, fish, animal fat, wild berries, tubers, etc. Paleo advocates believe that consuming these evolutionarily-preferred foods promotes optimal health.
These foods are the main staples of paleo, which is sometimes called the caveman diet — it’s a pre-agriculture approach to eating — no grains, no beans, nothing farmed or grown on purpose.
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 meal plan, your food choices include:
- Pastured or grass-fed meat, fish, eggs, and organ meats
- Fresh fruits and veggies (as much as you like, especially leafy greens)
- Healthy fats like coconut oil, olive oil, avocados (and avocado oil), butter, ghee, and palm oil
- Nuts (all kinds)
- Starchy roots and tubers (sweet potatoes, cassava, sunchokes, rutabaga, etc.)
- Naturally derived sweets like honey, maple syrup, and coconut sugar (these are technically allowed, but many trying to lose weight leave them out or use them sparingly)
On paleo, foods to avoid include:
- Industrial vegetable oils like soybean oil, safflower oil, and canola oil
- Refined sugar
- Grains (including whole grains)
- Anything processed
Because paleo bans grains, sugar, and beans, this diet is 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?
It depends on who you ask. Legumes, for instance, contain high levels of 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 same goes for whole grains.
The paleo argument against dairy is less clear. The claim is that hunter-gatherers didn’t drink milk, so neither should you. But here’s the thing. Many people, especially those of Northern European descent, have evolved to tolerate dairy. These people have more lactase, a special enzyme that digests milk sugar (lactose)[*].
Not all paleo sources shirk dairy, though. For those who can tolerate it, dairy has healthy nutrients and not necessarily counter to human evolution.
For better or worse, a strict paleo diet means eating exactly like ancient homo sapiens ate, which can be challenging at a modern-day supermarket or restaurant.
Like the paleo diet, the ketogenic diet leaves out sugar, grains, legumes, and industrial seed oils. Unlike paleo, the goal of keto is to promote a unique metabolic state called ketosis.
When you eat a very low-carb, high-fat diet like keto, your blood sugar and insulin levels stay low. This tells your body that carbs are scarce, so it’s 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 the keto diet plan — you start burning your fat stores instead of glucose to power your body. This can lead 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 in the 1920s: epilepsy.
Researchers had just discovered that fasting had anti-seizure properties. They surmised that if fasting worked so well for seizures, why not create a fasting-mimicking diet for children with incurable epilepsy[*]?
Keto was that fasting-mimicking diet. On a keto-style fast, you’re eating high-fat. You burn fat to fuel your energy needs rather than the glucose you’d be getting from carbs. Counterintuitively, a fast is a high-fat diet.
Among epileptic children, a keto diet reduced not only the frequency but also the intensity of their seizures. The more ketones a child produced, the fewer seizures the 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.
If your goal is weight loss, you probably want to know if paleo or keto is the way to go. It’s not a super-complicated question. The science should answer the debate on paleo vs. keto for you.
Keto for Weight Loss
The ketogenic diet is all about calculating your macronutrient ratios. On keto, you eat about 60% fat (high-fat), 30% protein (moderate protein), and 10% carbs (low-carb) by calories. You can give or take on fat or protein a bit, but carbs must stay under 10% to enter the ketone zone on this eating plan.
The main benefit of keto is metabolic. Fewer carbs, lower blood sugar, contained insulin, more fat burned, more weight loss. Pretty straightforward.
In addition to the metabolic benefit, the state of 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, fewer cravings.
Keto is like killing two birds with one stone for weight loss: You burn more fat, and 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 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[*].
- 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.
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 that’s the case.
Some researchers believe people lose weight on the paleo diet, not because ancestral dieting has special metabolic effects, but because people end up eating fewer calories on paleo[*].
This is also true of intermittent fasting (IF). IF means eating within a four- to 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. (It’s also possible to practice IF with keto.)
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[*][*].
It makes you wonder: Since paleo diets are often low-carb, could this explain weight loss on paleo?
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, but it’s harder to carb-binge on carrots than on, say, pasta. Also, removing processed foods on the paleo diet helps keep carbs low.
Low-carb eating can be an effective strategy to reduce body fat. But there’s nuance here. It’s possible to be low-carb, but not low-carb enough to reach a state of ketosis. In this case, your body will be in sugar-burn-mode, but there won’t be much sugar 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[*]. 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.
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.
When it comes to paleo vs. keto, much of it 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 offers 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 prefer paleo. These foods have too many carbs for a standard keto diet, but they’re fine by paleo standards.
If you 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 treat childhood epilepsy successfully[*].
The verdict: Both paleo and keto have restrictions, so compliance depends on your tastes, goals, and personality.
If you find you’re adding pounds rather than losing them on the paleo diet, here are some possible explanations.
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? 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
As it turns out, even healthy carbs can be unhealthy if you eat too many of them.
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 carb 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.
Eating Fat With Carbs
If you decided to write a book on the paleo diet, you might put sweet potato on the cover. Inside that sweet potato — open, orange, steaming — would be sizable pat of butter.
But here’s the issue. Combining fat and carbs (such as adding butter to your potato) can make weight loss more difficult.
Why? Because this combo is hyper-palatable. Together, carbs and fat taste so good that your dietary judgment flies out the window. Once you start, you can’t stop. They might be healthy foods, but even healthy foods can pack on the pounds if you overeat them.
In a recent study, researchers showed that a mixed meal of fat and carbohydrates triggered reward circuits of the brain — circuits that govern eating habits[*]. Participants loved these mixed meals so much 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 means lots of fat storage.
The takeaway: Carbs and fat together are hyper-palatable, insulinogenic, and could lead to weight gain.
Paleo vs. Keto: One 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 while favoring 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 on 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. To learn more about how to start a keto diet, check out this beginner’s guide to a keto lifestyle.