The ketogenic diet may be the “it” low-carb diet for weight loss right now, but its predecessor, the Atkins diet, is the original version of this restrictive eating approach. “Atkins and keto are both low-carb diets that may benefit weight loss, diabetes management, and heart health,” says Vanessa Rissetto, RD, a nutritionist based in Hoboken, New Jersey.
In addition to keto being much higher in fat than Atkins, a main difference between Atkins and keto is that you gradually increase your carb intake on Atkins, Rissetto says. Meanwhile, she adds, carbs “remain very low on the keto diet, allowing your body to stay in ketosis and burn ketones for energy.”
Today, the diet, also called the Atkins Nutritional Approach, comes in three versions. (1)
Atkins 20 is for people who:
Want to lose more than 40 pounds (lb)
Have a waist circumference of over 35 inches (women) or 40 inches (men)
Have prediabetes or type 2 diabetes
Atkins 40 is for people who:
Want to lose fewer than 40 lb
Are pregnant or breastfeeding
Require a diet with a wider variety of foods
Atkins 100 is for people who:
Want to maintain their current weight
Are pregnant
Are breastfeeding and trying to maintain their weight
Before trying any version of the Atkins diet — and especially if you are pregnant and considering any Atkins plan — check with your healthcare team.
An Overview of the 3 Atkins Diet Plans
All forms of the Atkins diet are focused on restricting what are called net carbs (including those in veggies) and emphasize eating protein and healthy types of fat. Select carbs are added back to your diet as you start approaching your weight loss goal.
Atkins defines net carbs as grams of carbs minus grams of fiber and grams of sugar alcohols. (Note that the U.S. Food and Drug Administration [FDA] does not recognize “net carbs” as an accepted nutritional term.) (2)
Atkins 20 and Atkins 40 involve various phases, while Atkins 100 is considered a lifestyle approach and calls for consuming no more than 100 net carbs per day. In Atkins 20, your initial, “induction” phase limits you to 20 grams (g) of net carbohydrates, while in Atkins 40, your induction phase limits you to 40 g of net carbohydrates, which gives you a little more flexibility in the foods you can eat in the beginning (including, for example, select fruits). (1) In Atkins 20, you add net carbs back to your diet in 5 g increments (20, 25, 30, and so on), while in Atkins 40, you add net carbs back to your diet in 10 g increments, explains Lauren Popeck, RD, of Orlando Health in Florida.
Atkins 20 Foods
To help jump-start your weight loss on the Atkins 20, you might consume some of the following foods:
Foundation veggies, such as broccoli, spinach, bok choy, and cucumbers
Protein, like eggs, chicken, and beef
All fish, including salmon, cod, flounder, and herring
Butter and olive oil
Some cheeses, such as cheddar, goat, Swiss, and Parmesan
You can find a full, comprehensive food list for phase one of the Atkins 20 on the Atkins website. (3)
Atkins 40 Foods
If you’re following the Atkins 40 plan, you can eat all of the above, as well as the following foods (so long as you keep net carbs under 40 g per day): (4)
Nuts and seeds
Legumes (beans)
Fruit
Starchy vegetables, like squash, potatoes, and beets
Whole grains, like barley, whole-grain rice, and whole-wheat pasta
Atkins 100 Foods
Atkins 100 followers can eat virtually all foods, so long as you do not exceed 100 g of net carbs per day. Carbs can add up fast if you’re eating sugar or refined carbs, so it’s best to limit or avoid those. (1)
The entire Atkins diet is available for free online.
The premise of the Atkins diet is that if you count and limit carbs — the body’s usual fuel — your body will be forced to burn your fat stores for energy, thereby promoting weight loss. As with many other fad diets, the main idea is to stop eating foods made with refined flour and sugar. But if you’re trying to follow the Atkins 20, even carb-dense whole-grain foods are on the don’t-eat list until you reach the maintenance phase.
“Cutting out carbs can contribute to weight loss initially. However, eliminating whole food groups, such as grains, milk, yogurt, and fruit, is likely unsustainable and inadequate in nutrients,” Popeck cautions. “Fiber will certainly be lacking, as well as calcium, potassium, and other vitamins and minerals.” (More on this in the cons section.)