What’s the Difference Between Keto and Atkins?

The two popular diets drastically reduce carb intake, but here’s how they stack up in terms of difficulty, safety, and results.

A keto plate can look like this.

If the most popular low-carb diets were ranked, the ketogenic diet and the Atkins diet would be neck and neck. “They both follow carbohydrate restriction,” says Erin Dolinski, RD, a clinical dietitian specialist at Beaumont Hospital in Royal Oak, Michigan.

We’re not just talking about cutting back on the bad-for-you carbs — the donuts, cupcakes, and cookies — but even things like fruit and some veggies. Limiting carbs as much as these diets require puts the body into ketosis, which means the body turns to fat for fuel once its glucose stores are depleted. Ketosis plays a role in each of the diets but in different ways, which could affect how sustainable the diet is in the long run.

An Overview of How the Atkins Diet Works

The Atkins diet was introduced in 1972 by a cardiologist named Robert Atkins, and it’s been popular on and off since, Dolinski says. The original version of the diet (now called Atkins 20) has four phases. The introductory phase of the diet kicks it off with by far the most restrictive rules.

Protein and fat are fair game on Atkins, but carbs are strictly limited to between 20 and 25 grams (g) of net carbs (total carbs minus fiber) during the introductory phase. Those carbs come from nuts, seeds, veggies, and cheese. “Having only that amount of carbohydrates can result in your body going into ketosis,” Dolinski says. You’ll stay in this phase until you’re about 15 pounds (lb) away from your goal weight.

RELATED: What’s the Difference Between Ketosis and Diabetic Ketoacidosis?

Phase two increases the carb allotment to 25 to 50 g, adding in foods like blueberries, cottage cheese, and yogurt. You’ll stay here until you’re about 10 lb away from your goal.

During the third phase, you’ll increase to between 50 and 80 g of net carbs as you try to find that perfect balance — how many carbs can you eat before the weight loss stalls? “It is done slowly, realistically, with some trial and error to see what amount of carbohydrates can be consumed again without causing any weight gain,” says Michelle Jaelin, RD, a Hamilton, Ontario–based blogger at NutritionArtist.com.

Once you figure that out and maintain it for one month, it’s on to phase four: Lifetime Maintenance. This part of the diet focuses on continuing the habits developed during phase three. Carbs are allowed (up to 100 g per day), as long as the weight doesn’t creep back on.

RELATED: How Do You Tell the Difference Between Good and Bad Carbohydrates?

An Overview of How the Ketogenic Diet Works

There are a lot of moving parts with Atkins and its four phases. The ketogenic, or “keto,” diet, on the other hand, promotes one way of eating for the entirety of the diet. You’ll cut your carbs down to about 5 percent of your daily intake. Seventy-five percent of your remaining calories will come from fat and 20 percent from protein. As a result of eating this way for a few days, you will enter ketosis, which you can monitor with keto urine strips if you choose.

The keto diet was first developed in the 1920s as a way to treat children with epilepsy, Dolinski says. Since then, research has linked the diet to weight loss, hence the many people without a history of seizures who have hopped on the bandwagon. A study published in November 2017 in Diabetes & Metabolic Syndrome: Clinical Research & Reviews found that subjects who followed the keto diet for 10 weeks had significant changes in weight, body fat percentage, body mass index (BMI), and HgA1c levels.

Still, Dolinski recommends the diet only for children with epilepsy, because cutting out entire food groups and drastically changing the way you eat poses a fair amount of risk. “The buildup of ketones can cause a lot of side effects, such as nausea, headaches, mental fatigue, and bad breath,” she says. It can also lead to deficiencies in essential vitamins and minerals and increase your risk of kidney stones and potentially heart disease, depending on the types of fats people choose.

RELATED: What to Eat and Avoid on the Ketogenic Diet

Similarities Between the Ketogenic Diet and the Atkins Diet

Will you lose weight on either of these low-carb diets? Most likely you will, if you follow them strictly.

Dolinski suspects you’ll mainly lose water weight in the beginning because carbs retain water. She suspects you’ll gain a lot of that back once you start eating normally again. A study published in November 2014 in Circulation: Cardiovascular Quality and Outcomes found that after one year, people who followed Atkins lost a modest amount of weight (4.6 to 10.3 lb), though some of the weight was regained by the end of year two.

You don’t have to count your calories on Atkins or keto. But you do need to track the number of carbs you take in. On keto, you also need to make sure you’re hitting the right percentages of calories coming from fat and protein.

As for which diet is easier to follow, Jaelin says it depends on the person and his or her eating habits before starting the diet. Neither one will be easy, though, because low-carb diets can lead to dizziness, nutritional deficiencies, and mental and physical fatigue, Dolinski says. U.S. News & World Report puts the Atkins diet’s “easy to follow” score at 1.8 out of 5 and keto’s at 1.4.

RELATED: Here’s What to Expect if You Try the Ketogenic Diet

A Look at the Differences Between Keto and Atkins

One key difference between the keto diet and Atkins is the amount of protein you’re allowed to take in. There’s no cap on Atkins, while keto limits protein to about 20 percent of your daily calories.

The other big difference is that keto centers on the body being in ketosis during the entire period of the diet, while ketosis plays a role only during phase one and possibly two of Atkins. On Atkins, you eventually reintroduce carbs, but on keto, carbs are always limited.

That means Atkins may be more sustainable in the long run because it’s not quite as restrictive and doesn’t require you to make sure your body remains in ketosis. Plus, on Atkins, you can eventually add back nutritious foods like quinoa, oatmeal, and fruit, the Atkins website notes.

RELATED: 8 Veggies That Make Great Low-Calorie Bread Substitutes

Which Low-Carb Diet Is Safer, According to Dietitians?

Jaelin says neither of these diets is recommended for people with diabetes, heart disease, or kidney disease. But without any of those chronic conditions, the diets can be safe if done short term, Jaelin says. A study published in American Family Physician found that low-carb diets are more effective than low-fat diets at lowering levels of triglycerides and A1C and raising levels of “good” HDL cholesterol.

The long-term safety of low-carb diets is a little iffy. Jaelin suspects that’s because dropout rates for studies involving low-carb diets are high. A study published in February 2017 in BMJ Open Diabetes Research and Care looked at 10 low-carb studies and found dropout rates ranged from 2 percent to 60 percent.

Considering giving one of these diets a try? Both Jaelin and Dolinski recommend speaking to a doctor or dietitian first.