Unless you’ve been living under a rock (or, ahem, in a cave), you’ve probably heard about the Paleo diet. One of the biggest food movements of the decade, it’s got everyone from clean eaters to CrossFitters and celebs eating like they’re a member of the Flintstones family.

According to Milk & Honey Nutrition founder Mary Ellen Phipps, MPH, RDN, Paleo’s philosophy reflects the way our (really distant) ancestors ate before agriculture, animal farming, and processed foods hit the scene. The diet’s devotees believe the human body runs best on things that can be hunted and gathered, and that more modern foods, like dairy products, legumes, and grains, aren’t genetically ideal for us. (The validity of this hypothesis, however, has been questioned by some researchers.)

In order to know exactly what our Paleolithic predecessors ate, you’d need a time-machine that sends you way back—like, back before HIIT was hot and spiralized vegetables passed as pasta. (From 12,000 to 2.6 million years ago, to be exact.) But since that’s not realistic, modern Paleo creator Loren Cordain, PhD, based the diet around the plants and animals that were found in the wild back in the day.

Intrigued by the prospect of getting ancestral with it? Consider this the beginner’s guide to all things Paleo: its benefits and pitfalls, the foods to eat (cookies included!) and avoid on the program, and how to experiment with Paleo living without diving all the way in. (Paleo-ish—it’s a thing!). See you when we return to the 21st century, whole grains…

Check out the video below to see what a registered dietitian thinks of the Paleo diet:

What can I eat on the Paleo diet?

In a nutshell—but not peanuts, those aren’t Paleo—the idea is to eat only what was available in the Paleolithic era. “The rules are simple: start eating meat, fish, fruits, veggies, nuts, eggs, seeds, healthy oils, and anything else our ancestors could have scoured from the earth,” says registered dietitian Bonnie Taub-Dix, RDN, creator of BetterThanDieting.com and author of Read it Before You Eat It—Taking You from Label to Table.

When it comes to eating meat the Paleo way, sourcing is important—after all, ancient animals weren’t eating industrialized food or being injected with hormones. “A super-strict Paleo lifestyle mandates choosing grass-fed, pasture-raised, and organic foods,” says Mary Shenouda, founder of The Paleo Chef and Phat Fudge, a Paleo-based performance food company. But if these options aren’t available to you, that’s okay. “The Paleo diet isn’t exclusive or just for people who can afford those higher-priced eats,” she says.

There are also a few modernized foods that are considered by many Paleo eaters to be okay—namely, ghee, honey, alcohol, bacon, salt, and coffee. “Coffee was definitely not consumed by our Paleolithic ancestors, but a lot of Paleo dieters do drink it black, without dairy or sugar,” says Maggie Michalczyk, RDN, founder of Once Upon A Pumpkin. The Paleo crowd’s not totally anti-booze, either. It’s recommended that if you’re going to drink, to do it in in moderation and choose distilled liquors like vodka, tequila, and brandy. Some also believe red wine is okay due to its high antioxidant levels.

Paleo-friendly foods include:

• Meat and poultry (beef, lamb, chicken, turkey, pork; choose grass-fed or organic if possible)
• Liver
• Seafood (choose wild-caught, if possible)
• Eggs (choose free-range or pastured if possible)
• Nuts (but not peanuts—they’re actually legumes)
• Seeds
• Fruit
• Vegetables
• Tubers (sweet potatoes, yams, turnips)
• Herbs
• Spices
• Coconut oil, avocado oil, extra-virgin olive oil

What can’t I eat on the Paleo diet?

This may come as no surprise, but you’ll have to nix a few foods when going Paleo—specifically, those that Stone Age folks wouldn’t have eaten. “You’re omitting gluten, both whole and refined grains, dairy, legumes, soy, sugars, processed foods, and things that can cause inflammation within your body,” says Shenouda.

The guidelines of Paleo eating may seem basic enough—eat this, not that—but successfully going cavewoman takes some savvy when it comes to processed foods. “I tell people if it looks like it was made in a factory or comes in a box, jar, or bag, it’s likely not Paleo,” says Taub-Dix.

Paleo no-go foods:

• Grains (whole grains, wheat, spelt, rye, barley, quinoa, oats, brown rice, and other gluten-free grains)
• Legumes (beans, peanuts, lentils, soy)
• Dairy (butter, cheese, yogurt, milk, ice cream)
• Some vegetable oils (soybean oil, grapeseed oil)
• Hydrogenated oils (margarine)
• Sugar and high-fructose corn syrup
• Artificial sweeteners
• Processed foods

Why are people so freaked by gluten, anyways? Learn more in our latest episode of You Versus Food: 

What’s a typical Paleo meal look like?

Okay, so you’re off to a good start. Your fridge looks like a farmers’ market and you’ve shed your pantry of all grains, peanut butter, and processed foods. What now?

Paleo meals actually don’t look all that different from what you might eat on a program like Whole30. “A typical breakfast for me might be a smoothie, eggs with turkey bacon, or lox,” says Shenouda.

Chicken salad, bunless burgers, salads, stir-fries, and grilled fish are all Paleo-approved lunch and dinner options, Michalczyk says. Just one caveat: When prepping for yourself, it’s important to remember that most sauces, marinades, and dressings are not Paleo-approved, as they often contain hidden sugars or not-so-healthy oils.

What about eating Paleo at a restaurant?

Sticking to a Paleo plan while eating out can be tricky, and that’s what Michalczyk considers its biggest downfall. “In general, very strict diets are harder to follow than more flexible ones, especially if you have a job or lifestyle that involves eating out frequently,” she says. Yes, it’s a possibility at your go-to fast casual chains—like Chipotle and even Olive Garden. You’ll just have to get a little specific—er, “creative”—with your order.

Shenouda says that you’ll get used to advance planning when you’re hitting up a restaurant. “Be patient. Think ahead. Call ahead of time to find out if the chef will be willing to work with you,” she advises. She’s had success using phrases such as, “I have these food requirements and restrictions. I will eat anything that the chef will prepare with those in mind.” When in doubt, she adds, some plain vegetables and a plain piece of meat are pretty safe bets. (And she brings Phat Fudge and an avocado with her wherever she goes, just in case.)

How should I work out on the Paleo diet?

You’ll often hear Paleo types referring to the program as a “way of life.” That’s because movement is another major part of the equation—after all, our ancestors used food primarily to fuel their constantly on-the-go lifestyles.

Paleo exercise is based on the same principle as Paleo eating: Move how you’re designed to move, and do it often. There’s no specific fitness regime recommended on the plan, but the goal is to be as active as possible. You may have heard that the plan is popular in CrossFit communities—and while functional fitness fans may have helped popularize the Paleo diet, you don’t have to go Paleo to try the popular workout, assures Phipps. (Or vice-versa.)

Okay, but is going Paleo actually good for you?

There are a few benefits of the Paleo diet that just about every wellness pro can get behind. “In general, removing processed foods from anyone’s diet will garner health benefits that are endless,” says Chenouda.  “Junk food isn’t the way to achieve optimal living and performance.”

It’s also super high in protein, which is great for athletes or anyone trying to put on muscle, Michalczyk says. Plus, since it’s dairy-free and grain-free, the Paleo diet is a good eating plan for people with those intolerances or allergies, she adds.

Phipps and Shenouda believe those suffering from chronic ailments associated with inflammation can benefit most from Paleo.  “As a registered dietitian, I recommend this plan as an anti-inflammatory protocol to help alleviate symptoms associated with lupus, MS, or arthritis,” says Phipps. Anecdotally, Shenouda has heard women say they’ve experienced relief from migraines, rashes, bloating, and IBS, among other issues.

Are there any reasons not to go Paleo?

As with any restrictive eating plan, there are a few drawbacks associated with the Paleo lifestyle. “When you’re saying bye to dairy, beans, and grains, you might miss out on some important nutrients, especially calcium, vitamin D, B vitamins, and fiber,” says Michalczyk. That’s why Phipps doesn’t recommend it for people who don’t need to eliminate dairy and grains for health reasons.

Other experts believe that you can still go Paleo and get all the nutrients you need, but you need to meal plan carefully. You’ll need to focus on getting vitamin D from foods like broccoli, mushrooms, and canned fish, and calcium from almond butter, chia seeds, greens, and cauliflower, Michalczyk says. Taub-Dix adds that eating enough liver, seafood, poultry, and vegetables can help combat the loss of B vitamins when you stop eating grains.

“The first few weeks, keep a food journal to track your Paleo food choices and how they are making you feel,” suggests Michalczyk. “Are you hungry? Are you hangry? Are you tired? Are you sad? Your body will help you figure out if this diet is making you feel good or not. If you’re feeling any of the above, it’s time to chat with a dietitian or doctor.” They’re the only ones who can tell you for sure whether you’re deficient in any nutrients.

Can I do Paleo halfway?

The short answer is yes—but it depends on why you’re trying Paleo. If you’re attempting to relieve specific symptoms, Phipps recommends following the diet strictly for at least six weeks, as that will give your body time to get used to it. (And if this is the case, you should also be doing it with the blessing and supervision of an expert.) But if your goal is to simply get away from processed foods, you’ve got some wiggle room. A paleo-vegan diet is a possibility, for example.

Shenouda recommends starting with a “PaleYOU” eating plan—basically, a Paleo diet tailored to meet your personal needs and goals, as opposed to the goals of the Paleo program. Michalczyk recommends going “Paleo-ish,” which involves eating Paleo five days a week, and not the other two.

You can also ease into it, says Taub-Dix—not a bad idea, considering that going from zero to 100 on meat and veggies can cause digestive distress in some people. “If you think the Paleo plan is for you but don’t want to go at it full-force, you can try just cutting some of your carbs,” she suggests.

When it comes to experimenting with different eating plans—whether it be Paleo, veganism, keto, or something else—what’s key, according to Michalczyk, is to do what’s sustainable over the long-term for you.

Originally published on August 22, 2018. Updated on December 26, 2019, with additional writing and reporting by Kells McPhillips.

If you’re ready to get started, try these pre- and post-workout Paleo eats. And learn how to whip up a batch of Stone Age-approved muffins.