Low-carb, paleo, keto…if it seems like everyone but you is off bread lately, it’s probably because they’re on one of these diets. And while the diets themselves aren’t exactly new, it certainly seems like a lot of people are suddenly cutting back, to some degree or another, on the macronutrient that has long been human beings’ primary source of energy.
While for some of us this idea is, tbh, flummoxing in and of itself (you can pry my bread and bananas from my cold, dead hands, thank you) it’s also confusing to even differentiate between all these popular diets. What is paleo vs keto? How low is low-carb?
We’ve got answers.
Before we get into the nitty gritty of paleo vs keto vs low-carb, though, it’s important to put this carb-slashing into the context of what the evidence tells us about diets in general. There is no best diet for everyone (or even most everyone), and while most diets can result in short-term weight loss, they also tend to fail in the long term. If weight loss is your goal, you should know that weight is determined by a multitude of factors beyond diet—many of which are out of your control—and it is not the only measure of health. For all of these reasons and more, it’s definitely advisable to first consult a doctor or work with an R.D. if you decide to begin a diet like low-carb, paleo, or keto. It’s especially important to check in with a health care provider before starting any diet if you have a history of disordered eating or any health conditions.
With all that said, if you’re just curious about what each one of these diets entails, we’ve got some helpful information. Here, we lay it all out: Where these diets come from, what they’re based on, how they’re similar to one another, and, most importantly, what you actually eat on them.
What eating “low-carb” actually means
“Low-carb” is a flexible, generic term that can describe any pattern of eating where you consume a fewer-than-average number of carbohydrates, New York-based dietitian Samantha Cassetty, M.S., R.D., tells SELF.
What’s average? It depends on who you ask. But as a baseline, we can work off the 2015-2020 Dietary Guidelines, which sets the Acceptable Macronutrient Distribution Range (AMDR) for each of the macros (carbs, fat, and protein). The AMDR represents the range of intake of a given macro that is associated with a decreased risk of chronic disease and sufficient intake of essential nutrients. Anything outside of the AMDR, and you may begin to potentially increase your risk of chronic disease or nutrient insufficiency, per the Dietary Guidelines.
For carbs, that target range is 45 to 65 percent of your total caloric intake. (So someone eating 2,000 calories a day would get 900 to 1,300 of their calories from carbs. Carbs contain 4 calories per gram, so that comes out to 225 to 325 grams.)
Then, “When you get less than 45 percent of your energy from carbohydrates, that’s where we generally start to classify diets as ‘low-carb,’” Jennifer Bruning, M.S., R.D.N., L.D.N., national spokesperson for the Academy of Nutrition & Dietetics (AND), tells SELF.
Beyond that, “low-carb” is not really a prescriptive diet. There’s a lot of leeway in how you reach that “under 45 percent” mark. “A low-carb diet can drastically reduce carbs and can be very restrictive, or it can be more moderate and inclusive of different foods,” Cassetty explains. Technically, a person getting 10 percent of their calories from carbs and a person getting 40 percent of their calories from carbs are both technically eating low-carb. There are also no foods expressly included or omitted, meaning you could stick to only low-carb foods or incorporate moderate portions of high-carb foods, like bread or potatoes. (Though, it is likely that your diet will naturally include more protein and fat to compensate for the reduction in carbs.) So ultimately, the degree to which you curb your carb intake and how you get there is up to you.
Under this umbrella are many specific diets that qualify as low-carb, each offering different roadmaps. For instance, the Atkins diet was one of the earliest branded low-carb diets to make its way into the mainstream back in the ‘90s. More recently, paleo and keto have become wildly popular. While they both are low-carb diets, that’s pretty much where their similarities end, Bruning says. Here’s the deal with each of them.
The idea behind paleo
“Paleo is meant to be a modern day approximation for the way our ancestors ate during the paleolithic area,” Bruning says, “roughly 10,000 years ago before the advent of agriculture when we were hunter-gatherers.”
The basic idea is that human beings are essentially genetically the same as our ancestors during that period. And, based on anthropological and scientific study of that era, the humans living then did not experience the prevalence of the chronic diseases that we do today, including heart disease, diabetes, and cancer, Jen explains. Paleo advocates believe that this lack of disease is in large part because of the vastly different way they lived, including the way they ate and exercised.
The origins of paleo
The idea of eating like our ancestors can’t be attributed to a single person. But Cassetty says the man largely credited with making paleo mainstream in the 21st century is Loren Cordain, Ph.D., a professor emeritus of the Department of Health and Exercise Science at Colorado State University. On his website, Cordain says he himself first encountered the paleo diet concept in a 1985 medical journal article.
Cordain laid out the principles of Paleo for the modern masses in his book The Paleo Diet in 2002, which went on to become a NY Times Bestseller. Although Cordain has trademarked The Paleo Diet® Movement, various iterations of the diet have emerged and “the paleo diet” (lowercase p) has been widely adopted by various food bloggers and influencers. (For simplicity’s sake, we’ll stick with Cordain’s original version.)
What you do and don’t eat on paleo
In paleo, the focus is more on what you eat than how much. “There is no counting or strict macronutrient breakdown to follow,” Bruning says, “only foods that are allowed or not.” In general, “The paleo diet promotes certain whole foods, but not others, and eliminates all refined foods,” Cassetty says.
The list of what you cannot eat on paleo is long, and includes pretty much anything that has to be cultivated or refined, as opposed to something that could theoretically have been scavenged by our ancestors. That includes a number of highly nutritious whole foods, like legumes (i.e. beans, lentils, peanuts), dairy, whole grains, and starchy vegetables like potatoes. It also covers added sugars, salt, and refined oils (like canola oil). And it cuts out any kind of packaged or processed foods. That includes both those generally lacking in nutrients (like candy, ice cream, and chips) as well as nutrient-packed packaged foods (like protein bars or fortified cereals).
Though eating paleo doesn’t necessarily mean you’ll be maintaining a low-carb diet, the wholesale elimination of several categories of carbs (both whole and refined), as well as the emphasis on protein and fat make low-carb eating a common outcome of following the paleo diet, Bruning explains. But people on paleo can still end up getting about 35 to 45 percent of their calories from the kinds of carbs that are allowed, according to Cordain’s site—namely fruits and vegetables, such as berries, citrus fruits, squash, and sweet potatoes. (So you get a hefty amount of fiber with your carbs, too.)
The list of what you can eat on paleo is relatively lengthy too, and includes a wide variety of whole foods: Fish and seafood, grass-fed meat, eggs, fruits, non-starchy veggies, nuts, seeds, and unrefined vegetable oils (like olive oil, coconut oil, and avocado oil). When it comes to animal products, there is an emphasis on the source, Cassetty says. For instance, beef should come from grass-fed cows, eggs should come from cage-free chickens, and fish should be wild-caught. And produce should be fresh whenever possible.
The idea behind keto
Keto is a more drastic low-carb diet because it requires significantly reducing (and carefully tracking) your carb intake. Unlike paleo, keto is all about the counting. The idea is to maintain a very precise balance of fat, carbs, and proteins in your diet in order to force your body to change the way it sources energy. “Having a firm understanding of the macronutrients in the foods you’re choosing is paramount in keto,” Bruning says.
Usually, glucose is the body and brain’s preferred form of fuel. We get glucose from carby foods, so when we severely restrict carbs, the body is deprived of fuel. So it turns to plan B and begins breaking down fat to produce a secondary energy source called ketones. This metabolic state, called ketosis, is the goal of the keto diet. However, it’s very difficult to stay in ketosis, Bruning says.
Keto is very different from your garden variety low-carb diet because it restricts carb intake to just 5 to 10 percent of your energy intake, Bruning says. Generally, that means consuming fewer than 20 to 50 grams of carbs a day. Most of the rest of your diet, about 70 to 80 percent, is fat, and 10 or 20 percent or so is protein. “Fat is the huge majority of the calories, carbs are very intentionally suppressed, and you get a moderate amount of protein,” Bruning says, adding that too much protein can interfere with ketosis.
The origins of keto
The keto diet has actually been around for about a century and has a surprising history. It was originally developed as a tool to help treat epilepsy that did not respond to other drugs, and has more recently been shown to be effective in doing so. (Scientists are still figuring out exactly why that is.) But in the past couple years, with the increasing popularity of low-carb diets of all sorts, keto has arrived as the ultimate anti-carb diet, with many of its advocates reporting weight loss as a result.
What you do and don’t eat on keto
Keto is all about fat-loading and carb-avoiding, so the bulk of the keto diet is foods that are high in fat and free of or very low in carbs. While there aren’t technically any specific foods you have to eat or avoid, Bruning says, there are only so many high-fat, low-to-no carb foods out there. So staples typically include full-fat dairy (like butter, cream, and cheese), eggs, oils, fattier meats (like bacon or fatty cuts of steak), fish, avocados, and low- or no-carb veggies like leafy greens, nuts, and seeds, Bruning says. You can also have low-sugar berries, like raspberries, in very small amounts. In addition to these fatty whole foods, you increasingly see “keto-friendly” snacks appearing on grocery store shelves. Unlike on the paleo diet, these processed foods are allowed on keto, as long as they remain within your macro limits.
What you cannot eat, obviously, is carbs. Technically, Bruning points out, no food is strictly off-limits—you could eat a few bites of cake and have zero carbs for the rest of the day and still hit the correct macro distribution. But in practice, most people don’t find that feasible and instead severely limit or eliminate all carb-rich foods—grains, fruits, legumes, sugar, and starchy vegetables. (This can also make it tricky to get a lot of fiber.)
But given that every carb matters when you’re striving to eat so few of them, even low-carb foods that are allowed on the diet, like nuts and veggies, have to be eaten sparingly, Cassetty says. “The carbs in non-starchy veggies and nuts count towards [your carb quota], so you can’t just eat all of those you want,” Cassetty says. “On keto, you really need to moderate everything that’s not pure fat.”
The bottom line
While all these diets go about limiting carbs in different ways and to varying extents, what they have in common is that they are, ultimately, pretty restrictive ways of eating. And that’s certainly not the right path for many people.
If you are interested in pursuing one of these diets, then it’s a good idea to consult a healthcare provider first. That may mean checking in with your primary care doctor or talking to any specialists you see about whether they have any concerns about how a certain diet could affect a medical condition. And ideally, you would work with a registered dietitian to help you incorporate as broad an array of nutrients into your diet as possible.