THERE'S NO shortage of trendy fad diets out there.

There's Whole30 and Noom. There's something called the Coffee Diet and another thing called the Sirtfood Diet. There are soup-based diets and cabbage-based diets and so many diets that it can feel like the world needs a way to lose a lot of these excess diets: a diet for diets.

So let us, for the purposes of popularity, look at just two of the most of-the-moment diets right now: the Keto diet and the Paleo diet.

These two diets, despite the divisiveness between the camps who claim that each of these diets are the most effective, actually have a lot of things in common.

They focus on three macronutrients: fat, protein, and carbohydrates. They involve closely tracking those three macronutrients. They can, at least in the short-term, provide some pretty powerful weight-loss results.

All that said, both diets are also highly restrictive, and will eliminate or drastically reduce some of your favorite foods (say goodbye to deep-dish pizza). And they are—just leveling with you here—pretty difficult diets to maintain long-term, both in terms of general enjoyment and food-related sanity.

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If you're interested in either of these diets (and you are aware that you don't need to go on a diet to have a healthy diet), it's important to know the basics of each, and how they compare to one another.

To help you sort out the nuances between Keto and Paleo, we talked with registered dietitian Kristen Kizer, of Houston Methodist Hospital in Texas.

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What is the Paleo Diet?

THE PALEO DIET focuses on foods that are high in protein and rich with fiber.


There's a strong emphasis on meat, fruits, and vegetables—basically, anything our ancestors would have consumed more than 10,000 years ago during the Paleolithic era.

(There's actually some truth to this: in July 2018, when researchers identified the stomach contents of the 5,300-year-old mummy Otzi, they found that his last meal was high-fat and contained "animal and plant remains," making it pretty Paleo-friendly.)

Because hunter-gatherers like Otzi had limited technology, obviously things like frozen pizza aren't allowed on the diet. But many foods that are considered healthy, like whole grains and legumes, are also not allowed.

Although Paleo is not strictly low-carb, eliminating processed foods makes it lower in carbohydrates than the average American diet. Most of your carbs will come from fruits and vegetables on this plan.

What is the Ketogenic Diet?

LIKE THE PALEO Diet, the Keto Diet restricts grains, rice, and other high-carb foods.

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But the primary goal of the Keto Diet is to put your body into a state of ketosis, which is when your body uses fat instead of carbohydrates as its primary energy source. When your body enters ketosis, fat travels to the liver and makes an acid called ketones, which enter your bloodstream and are converted into energy.

Unlike Paleo, Keto severely limits carbs and eliminates fruit and some starchy vegetables. For your body to enter ketosis, a good percentage of your calories (generally, somewhere between 60 to 80 percent, according to keto experts) needs to come from fats (this is why people frequently associate the Keto Diet with foods like bacon, even though most nutritionists say it's better to eat healthier items like avocados, nuts and seeds, eggs, and lean meats).

The idea is that all of that fat-burning will help you lose weight, says Kizer.

Is Paleo or Keto stricter?

ESSENTIALLY ALL legumes, dairy, refined sugar, potatoes, processed foods, refined vegetable oils, and salt (yes, you read that right), are off-limits on the Paleo Diet.

So what's left?

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Men's Health Plant-Based Eating: (The Diet That Can Include Meat)

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Grass-fed meat, seafood, fresh fruits and vegetables, eggs, nuts and seeds, and certain oils like coconut, avocado, and olive oils.

A paleo-friendly dinner might include grilled chicken with steamed vegetables, avocado and fruit.

If you think paleo is rigid, keto is even less flexible. Because only about 10 percent of your daily diet can come from carbs, that means you can only eat very limited amounts of even healthy foods that have natural sugars, such as certain fruits and vegetables,

Generally speaking, dieters are advised to eat between 20 to 30 grams of carbohydrates per day in order to maintain ketosis. To put this into perspective, a quarter cup of steel cut oats has 29 grams of carbs and a banana has roughly 27 grams of carbs.

So if you have a few bites of oatmeal or a small piece of fruit, whoops. That's your carb intake for the day.

"Paleo definitely gives people more flexibility," says Kizer. People are free to eat starchy vegetables and fruit, as well as foods rich in healthy fats like avocados.

Is Paleo or Keto better long-term?

WHAT DIFFERENTIATES a fad diet from a healthy one is whether you can maintain your health and keep the weight off in the long run. So where do Paleo and Keto stack up?

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The Paleo Diet: Because this diet doesn't require you to maintain ketosis, there's no need to weigh your food, as some do on the Keto Diet; nor do you have to closely monitor your carbohydrate intake. Plus, most people think of Paleo as a lifestyle rather than a diet, according to Kizer, so it's easier to stick to in the long run.

The Keto Diet: Eating a banana or too many nuts could knock you out of ketosis, which makes tracking your food intake necessary to stay on track for your weight loss goals. "Keto caters to people who are diligent," says Kizer.

For this reason, most people go in and out of ketosis because they have a hard time sticking with the diet. "Sometimes people try and teeter into it and they won’t lower their carbohydrates enough," registered dietitian Melanie Boehmer of Lenox Hill Hospital previously told

Plus, Kizer says, people usually jump on the keto bandwagon to lose weight, so they rarely attempt to stay in ketosis forever.

The winner: Paleo. Bacon or no bacon, Paleo is a less labor-intensive diet, which makes it easier to stick to in the long run.

Does Paleo or Keto have worse side effects?

It's common to feel lethargic as your body adjusts to the low-carb Paleo Diet. However, your energy levels will typically be restored within a few weeks.

Additionally, “while the paleo diet has plenty of protein and fiber, it is sorely lacking in calcium and vitamin D, mainly because of the omission of dairy products,” Roger Adams, Ph.D., founder of Eat Right Fitness, previously explained to Men's Health.

Over time, this could weaken your bones and immune system, which makes it important to eat plenty of calcium-rich (and paleo-friendly) foods like broccoli and dark leafy greens.

The extremely low level of carbs on the Keto Diet can cause what's known as the keto flu, which causes headaches, nausea, muscle cramping, and fatigue. Like the Paleo Diet, these unpleasant side effects generally subside after a few weeks. Drinking plenty of water and getting a full night's sleep should help.

As with paleo, doing keto for more than a few weeks could lead to nutrient deficiencies according to Andy Yurechko, MS, RD, of Augusta University Medical Center in Georgia .

He says lack of fiber is the biggest concern for keto fanatics, who may experience constipation. But it's possible to get fiber by eating lower-carb vegetables like broccoli and chia seeds.

Both diets come with some unpleasant side effects, but Yurechko doesn't advise sacrificing fiber to try keto in the long run.

Will Paleo or Keto help you lose more weight?

ON PALEO, eating like your ancestors doesn't guarantee you'll lose weight.

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While the diet emphasizes plenty of foods that are good for weight loss, such as lean protein and fruits and vegetables, you would still need to eat fewer calories to drop a few pounds. So if you're binging on nuts and fruit, you could actually gain weight on the Paleo Diet.

While ketosis isn't a magic recipe for weight loss, Konstantinos Spaniolas, Associate Director of the Stony Brook Metabolic and Bariatric Weight Loss Center in New York, says that people successfully lose weight on keto because they tend to eat less.

"They can stick to a relatively lower caloric intake because of the reduced cravings," he explained to Some online transformation stories even suggest you can lose as much as 200 pounds on the Keto Diet.

The winner: The Keto Diet. With an important caveat: These results are often short-lived, says Kizer. "When people come off ketosis, they gain weight," she says.

Is Paleo or Keto the better diet?

BOTH KIZER and Yurechko agree that Paleo is the better option in terms of overall health, simply because it's less restrictive and includes plenty of fruits, vegetables, and lean protein.

"Paleo is a little bit easier to have that balanced, moderate approach. Someone doesn’t have to become afraid of carbohydrates," Kizer says.

What's more, she believes keto could cause people to obsess over their carb intake and develop an unhealthy relationship with food. "When did we start worrying about the carbohydrates in nuts?" she says.

Of course, most dietitians say the best diets are sustainable and include options from every food group.

"This is the problem I have with all of these fad diets," Yurechko says. "A healthier type of diet is something you can do every day of your life."

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Melissa Matthews
Health Writer
Melissa Matthews is the Health Writer at Men's Health, covering the latest in food, nutrition, and health.
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Paul is the Food & Nutrition Editor of Men’s Health. He’s also the author of two cookbooks: Guy Gourmet and A Man, A Pan, A Plan.