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Atkins vs Keto: A Complete Comparison Of The Two

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Although there are certainly similarities between Atkins vs keto diets, there are also differences to take note of. 

So, what is the difference between keto and Atkins diets? What are the foods that you can eat on Atkins vs Keto diets? Is keto vs Atkins better for weight loss or health, or do people lose more weight on the Atkins diet than on the keto diet?

In this guide, we will discuss the differences between the keto diet and Atkins diet, including Atkins vs Keto diet principles, foods, and general pros and cons of each one.

We will look at: 

  • What Is the Atkins Diet?
  • What Is the Keto Diet?
  • Atkins Vs Keto: Similarities
  • Atkins Vs Keto: Differences

Let’s get started!

A sign that says low carbs surrounded by foods such as fish, cheese, oil and vegetables.

What Is the Atkins Diet?

Before we compare the primary differences between the Atkins diet and keto diet, it’s helpful to briefly discuss what each diet entails.

So, what is the Atkins diet?

The Atkins diet has been one of the most popular low-carb diets since it was first introduced in 1972 by a cardiologist named Dr. Robert Atkins.

Since the original inception of the Atkins diet, various iterations and modifications have evolved, and the Atkins diet has come in and out of prominence several times over the past 50 years.

The original Atkins diet is now called Atkins 20, and it has four phases.

The first phase of the Atkins 20 diet is the introductory phase, and it is particularly restrictive to help jumpstart weight loss.

Blocks that spell out Atkins Diet.

During the introductory phase of Atkins 20, you can only eat a total of 20 to 25 g of net carbohydrates per day.

The Atkins diet centers around this concept of “net carbs,“ which essentially refers to the total number of carbohydrates minus the number of grams of fiber.

Note that 20 to 25 g of net carbs per day is quite low, so many people find the first phase of the Atkins diet to be quite challenging, but the goal is to bring the body into a state of ketosis, as is the case with the keto diet.

The carbs in the introductory phase of the Atkins 20 diet are supposed to come from cheese, nuts, seeds, and non-starchy vegetables like leafy greens, broccoli, cauliflower, and asparagus.

There is no universally defined number of weeks that you are to do the Atkins diet introductory phase; rather, you have to remain in this phase until you are within 15 pounds of your goal weight.

Thus, depending on how much weight you want to lose on the Atkins diet, you may remain in this highly restrictive phase for several weeks to many months.

Phase 2 of the Atkins 20 diet is similar to the introductory phase except that the net carbs get bumped up to 50 grams per day.

High fats foods like fish and nuts.

You’re also allowed to expand your list of carbs to include foods like yogurt, cottage cheese, and blueberries.

You have to stay in the second phase of the Atkins diet until you are within 10 pounds of your goal weight.

The third Atkins diet phase increases the daily net carb intake to 80 g per day.

You are supposed to stay in this phase until you have reached your goal weight and maintained that weight for at least one month.

You also should not move onto the fourth phase once you have determined the proper balance of carbs that you can eat without hitting a weight loss plateau. 

In other words, you have to determine how many net grams of carbs per day you can have before your weight loss stalls.

Finally, the fourth phase of the Atkins diet is your lifetime maintenance phase. 

This is the indefinite phase where you should be following the general Atkins diet meal plan with a maximum daily allotment of 100 grams of carbs per day unless your own biochemistry and physical activity needs determine that you need to consume fewer carbs per day to maintain your goal weight without your weight creeping up again.

A notebook page that says Keto Diet.

What Is the Keto Diet?

The keto diet, or ketogenic diet, is a high-fat, very low-carb diet initially developed in the 1920s to help treat epilepsy. However, it is now a popular weight loss diet and is used to help manage blood sugar and reduce inflammation.

The keto diet puts the body in a state of metabolic ketosis, in which ketones are burned for fuel due to a lack of available carbohydrates.

Keto experts suggest that the keto diet should involve consuming 70–75% of your calories from fat, 20-25% of your calories from protein, and 5% of your calories from carbohydrates. 

Atkins Vs Keto: Similarities

Both Atkins and keto fall under the umbrella of “low-carb diets “ because they limit carbohydrate intake quite significantly.

The greatest similarity between keto vs Atkins occurs during the introductory phase of the Atkins diet, where carbohydrate intake is limited to only 20 to 25 g per day. This is similar to the number of grams of carbs permitted on the keto diet for most dieters.

A burger with avocado instead of bread as buns.

The physiological result of such a low-carbohydrate intake is, therefore, similar to phase 1 of Atkins vs keto: a state of ketosis.

Furthermore, whether you start the keto diet or the Atkins diet, you will likely drop a significant amount of weight right off the bat due to the release of body water once you burn through your glycogen stores.

Another similarity between the keto and Atkins diets is that neither diet requires you to count calories, which differentiates these diets from any other popular weight loss diet in which counting calories is an integral part of losing weight on the diet.

However, you do need to count your macros, at least in terms of the number of carbs you are eating on the keto diet and Atkins diet, in order to stick within the parameters of each low-carb diet.

Finally, although subjective, one other similarity between the ketogenic diet and Atkins diet is that both diets are quite restrictive in terms of the foods you are able to eat and the daily macros you have to stick within.

Fried eggs and vegetables.

Atkins Vs Keto: Differences

Despite sharing some similarities, there are also some notable differences between keto vs Atkins diet plans.

Here are some of the main differences between keto and Atkins diets:

Atkins vs Keto: Protein Intake

One primary difference between keto and Atkins is the amount of protein you can eat.

Although both diets are thought to be high-protein diets, the truth is that the keto diet is actually a high-fat diet, and you are supposed to limit your protein to about 20% of your daily caloric intake. 

On the other hand, there is no limit to how much protein you can eat on the Atkins diet in terms of grams of protein per day or percentage of total daily calories from proteins.

A cutting board with different foods and the percentages of macro nutrients for the Keto diet.

Atkins vs Keto: Ketosis

Another major difference between the Atkins and keto diets is the necessity to be in ketosis.

By definition, the ketogenic diet is designed to induce ketosis and keep you in a state of metabolic ketosis throughout the duration of the diet by limiting not only the carbs but also the protein you can eat per day.

While phase 1 of the Atkins diet generally puts you in a state of ketosis because of the very low net carb intake, because there is no cap on the amount of protein that you can eat, and the concept of net carbs is more lax than absolute grams of carbs, not everyone will remain in a state of ketosis even during the introductory phase of Atkins.

Furthermore, as you progress through the other phases of the Atkins diet, the more generous net carb allowance will pull you out of sustained ketosis.

You may be in ketosis during certain portions of the day depending on the timing of your meals and your carb intake, but you will not be in prolonged ketosis as you should be with keto vs Atkins.

A salad with seeds.

Atkins vs Keto: Foods

In general, the Atkins diet is less restrictive than the keto diet, especially as you progress through the phases. 

This may potentially improve adherence to Atkins vs keto. In fact, some studies have found that the dropout rate for the keto diet may be as high as 84%. 

If you aren’t able to stick with the diet, you won’t reap the health and weight loss benefits of keto.

Plus, the higher carb intake on the Atkins diet vs keto diet gives dieters on Atkins the opportunity to incorporate some healthy foods that are eliminated on the keto diet such as more fruits, vegetables, legumes, and small amounts of healthy whole grains like quinoa and oatmeal.

For this reason, it is often also easier to get more fiber on Atkins vs keto.

Interested in how the keto diet stacks up to another popular diet? Check out our comparison of keto vs paleo here.

Colorful post it notes with different diet names written on then.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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