Atkins and keto are both low-carb diets that may benefit weight loss, diabetes management, and heart health.
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. Meanwhile, remaining very low on the keto diet, allow your body to stay in ketosis and burn ketones for energy.
Today, the diet, also called the Atkins Nutritional Approach, comes in three versions.

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), or
• Have prediabetes or type 2 diabetes

Atkins 40 is for people who:
• Want to lose fewer than 40 lb
• Are pregnant or breastfeeding, and want to lose weight
• 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 Atkins 100 – check with your healthcare team.

What’s Involved in the 4 Phases of the Atkins Diet?
The Atkins 20 and Atkins 40 versions of the diet are divided into different phases.

Phase 1
The first phase, induction, can last from as little as two weeks to many months, depending on your goals.

Phase 2
The next phase, which focuses on ongoing weight loss, allows you to gradually increase your daily carb total.
Atkins 20 During phase 2 of Atkins 20, you’ll add more net carbs in 5 g increments and add variety to your diet with antioxidant-rich berries, some nuts and seeds, and more vegetables.
(In the Atkins 20 plan, there are technically two phases here: phase 2 and phase 3, with phase 3 starting once you’re within 10 lb of your goal weight. Both phases focus on adding carbs back into your diet while you continue to lose weight.) Atkins 40 During phase 2 of this plan, you add more carbs in 10 g increments primarily by increasing your portion sizes. The diet recommends moving into this phase when you are within 10 lb of your goal weight.
You can keep increasing carbs on both plans until you see weight loss slow or stop.

Phase 3
The final phase, which you start when you’ve reached your goal weight and have maintained it for at least a month, is a lifetime weight-maintenance plan, keeping daily net carbs to about 80 to 100 g.

The Top Foods to Eat and Avoid on the Atkins Diet
All plans recommend avoiding sugar and refined carbs, Popeck explains. In addition, here are some of the main foods you’ll be tasked with eating and avoiding on each plan.
Eat: foundation vegetables like spinach, cauliflower, broccoli, and more; healthy fats like olive oil and butter; nuts and seeds; and most cheeses.
Avoid: fruits like pineapples and mangoes; and starchy vegetables, like potatoes; and grains, at least initially.