What is the Atkins diet? How the original low-carb diet meal plan works and if you should try it

• The Atkins diet is a low-carb diet divided into four phases and designed to help you lose weight.
• Unlike keto, the Atkins diet encourages you to incorporate carbohydrates back into your meals.
• However, some dietitians don't recommend Atkins as it may be too restrictive.

Robert C. Atkins developed the Atkins diet in the 1960s. In short, it's a low-carbohydrate diet with the idea that if you limit the number of carbohydrates you eat, you'll lose weight. Basically, it's an early version of the keto diet - but with some key differences.

The height of the diet's popularity was in the early 2000s when one out of 11 Americans said they were on some type of low-carb diet, of which Atkins was a popular choice.

Since then, the Atkins diet has fallen out of favor for other popular restrictive diets like intermittent fasting and the keto diet.

Here's what you need to know about the Atkins diet, if it works, and how to tell if it's the right option for you.

The three versions of the Atkins diet

Depending on your weight loss goals, the Atkins website recommends following one of their three eating plans:

• Atkins 20® where you start out by eating 20 grams of net carbs per day.
• Atkins 40® where you start out eating 40 grams of net carbs per day.
• Atkins 100™ where you start out eating 100 grams of net carbs per day diet plan.

The four phases of the Atkins diet

Once you've chosen an eating plan, you'll go through four phases of the Atkins diet that will gradually reintroduce carbohydrates into your diet over time. The last phase is designed to help you develop the Atkins diet as a lifetime way of eating.

The four phases are as follows:

Introduction: This is the most restrictive phase of the diet and is meant to kickstart weight loss. In this phase, you are limited to 20 grams of carbohydrates a day. This phase forces your body into ketogenic metabolism - meaning that the extreme lack of carbs forces your body to burn fat for energy. In this phase, you will eat mainly proteins, fats, and low-carb vegetables like leafy greens.

On-going weight loss: In this phase, you can begin to gradually introduce more carbs back into your diet. Your daily carbohydrate intake can go up by 5 grams a week (maxing out at an additional 40 grams per week) and you can begin to diversify your food options. In phase two, you can eat nuts, seeds, and berries. If your goal is to lose 14 pounds or less, you can start here and skip the restrictive first phase.

Pre-maintenance: During this phase, you can increase your carb intake by 10 grams a week (maxing out at an additional 100 grams per week) so that you can find your carb balance. This is the fine-tuning stage of the diet and it is important to make sure you are keeping an eye on your goal weight. If weight loss stalls, you should dial back your carb intake again. This phase has more relaxed dietary restrictions and you can start to eat beans, starchy vegetables, and grains.

Lifetime maintenance: Phase four should ideally last a lifetime and is all about having relatively few restrictions, but maintaining the tools to make healthy choices. If you begin to gain any weight, the company recommends reducing your carbohydrate intake by 10 grams at a time.

Atkins is unlikely to be any better than simple calorie restriction

Though some people are drawn to the discipline and guidance that the Atkins diet offers, there is little evidence that Atkins is the best way to lose weight.

"Research shows that weight loss is typically achieved with calorie restriction, not specifically carbohydrate restriction," says Tony Castillo, MS, RDN, LDN, nutrition consultant for RSP Nutrition.

Based on a review, published in 2019 in the journal Nutrients, of studies exploring low-carb and low-fat diets related to weight loss, researchers report that there's not enough evidence to conclude that low-carb or low-fat diets are any better at helping people lose weight and keep it off than restricting calories.

And while low-carb diets like Atkins have been shown to help people lose weight faster, that's not the case long-term.

"Some research shows an increase in weight loss when a low carbohydrate diet is followed, after six months," says Castillo. "However, after one year on a low-carbohydrate diet, there is no difference in weight loss when compared to other calorie-restricted diets."

How to tell if you should you try the Atkins diet

Castillo recommends proceeding with caution before trying to adopt a new diet like Atkins.

"Prior to starting any diet it is important to always consult with both a registered dietitian and your physician, as there may be certain instances where a low-carbohydrate diet may not be the right fit for you," he says.

For example, the diet would not work for, highly "active individuals since carbs are the main source of energy for the body," he says.

He adds that there are often unwelcome side effects. "Typically, low carbohydrate diets can cause you to feel weak, fatigued, constipated, dizzy or even cause headaches, which is why it is important to consult an expert prior."

According to Castillo, the most important factor to consider is that going on the Atkins diet may lead to a deficit in fiber and essential vitamins and minerals, so a comprehensive plan would ensure these nutritional needs are met.

Insider's takeaway

Castillo's final opinion on Atkins is, "I believe in the long term Atkins is too restrictive."

Instead, he recommends, "a diet that won't cause nutritional deficiencies would include all types of foods," he says. Meaning, fresh, whole foods that can give you your daily value of essential nutrients including vitamins, minerals, healthy fats, and protein that are important for good health.

Some diets that experts recommend for good health long-term include the Mediterranean diet and the DASH diet.

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