South Beach Diet vs. Keto Diet

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Written by Brenda Peralta, Registered Dietitian and medically reviewed by Abby Courtenay

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The South Beach diet and the ketogenic diet are two of the most popular diets people often do when looking to lose weight. Nowadays, people are more concerned about their health and weight management — no wonder why people often research which is the best diet for them.

The answer is simple. The best diet is the one that you can sustain for a long time. However, how do I know which one is the one for me?

In this article, you will learn the difference between the ketogenic diet and South Beach. Learn what they are, similarities and differences between them, and the benefits and side effects that you may get from each one. We’ll also take a look at the differences regarding food choices and which is the most expensive.


What is the South Beach diet?

So, let’s begin learning about South Beach. Cardiologist Dr. Arthur Agatson designed this diet to aid in patients’ weight loss and help decrease their cholesterol levels.

The diet is based on the Atkins diet. Dr. Agatson saw that people following the Atkins diet lost a lot of weight, but he was uncomfortable with the high amount of saturated fats they were consuming. Also, he didn’t want to restrict healthy carbs like whole grains and fruits.

Therefore, this diet doesn’t restrict carb intake entirely. It focuses on whole natural products, thus limiting the intake of sweets and highly processed carbs. Additionally, it focuses on eating healthy fats and lean protein.

This diet is divided into three phases.

  • Phase 1 (1-14 days). This is the strictest stage of the diet. Here you greatly limit your carb intake. You focus on eating lean protein, healthy fats, legumes, and non-starchy veggies.
  • Phase 2. After 15 days have passed, you go into phase 2. You stay in this stage until you reach your weight goal, so it can last months. Here you can include the same foods as Phase 1, plus small portions of fruits, grains, and alcohol.
  • Phase 3. Once you get to your desired weight, you enter phase 3. No foods are off-limits, as long as you eat them in moderation, but you apply the rules and portion sizes you learned in phase 2 to keep your weight off.


Similarities between both diets

Although it may not seem like it, South Beach and keto have several similarities.

1. Foods that you are NOT allowed to eat

Neither diet allows processed, refined foods like sugars, pastries, or cookies. In both of these diets, you need to limit the consumption of these types of carbs.

2. Average weight loss

The primary purpose of these diets is often weight loss. Thus, either one you decide to choose can be a great option if you want to shed those extra pounds off. On average, you can lose 1-2 lbs. each week.

3. Cardiovascular disease

Both have compelling evidence for heart disease. They may help lower bad cholesterol levels, improve good cholesterol, and reduce triglycerides. Hence, if you have a higher risk of heart disease, you may want to speak to your doctor about whether one of these eating plans could help reduce your risk.


Differences between keto and South Beach

There are also some differences that might help you decide which is the one for you.

1. Macros

One of the biggest differences is the macronutrient composition of these diets.

A ketogenic approach is a low-carb, moderate-protein, and high-fat diet. When it comes to South Beach, there is no specific recommended macronutrient composition. It mainly focuses on which types of food you should be including. You can make it low-carb, but it is not as restrictive as keto.

2. Food quality

Although most keto experts recommend limiting your intake of saturated fats, it is possible to stay in ketosis without doing so. On the contrary, South Beach focuses on reducing saturated fats to prevent developing heart disease.

3. South Beach has phases

Another difference is the distribution of phases. Keto doesn’t have phases for you to transition in and out of, while South Beach is composed of three phases for you to follow, starting with the most restrictive.


Benefits of South Beach and keto

Although South Beach doesn’t have as much of a carb restriction as the ketogenic diet, you still have a reduction in carbohydrates. This means that you can get similar benefits from both of them.

Here is a list of the most common benefits you might experience when following either one.

  • Weight loss
  • Reduced cravings
  • Improved blood work
  • Increased energy levels
  • Improved consumption of whole foods
  • Decreased consumption of ultra-processed and fast foods
  • Increased insulin sensitivity
  • Decrease in inflammation
  • Increased satiety levels


Side effects of the South Beach diet and keto

Since phase 1 and keto are the most similar when it comes to comparing these two diets, here are the most common side effects you can get when doing phase 1 of South Beach and keto.

  • Low-carb flu. During the first days, you might experience nausea, headache, and foggy brain during the first days.
  • Reduced performance. While your body adapts to ketones, you might experience decreased energy levels, affecting your performance.
  • Nutrient deficiency. Since you eliminate a significant food group, you might not get all the nutrients that you need. To prevent this from happening, focus on eating a variety of foods, not the same thing everyday.
  • Constipation. Fiber is mainly found in carbs. Thus, by reducing carbs you might experience constipation. Fruit and veggies are also a good source, add more veggies to your diet to help prevent this.

During the other phases of South Beach, you start adding more carbs, so you might not experience these side effects.


Keto vs. South Beach: what to eat and avoid

Keto and South Beach have similar foods that you can eat. However, it depends on the phase that you are in. Phase one has the most food restrictions, you can then add carbs in phase two, and in phase three you can add more variety.

The following table breaks down the foods you can add to each phase. Those allowed in phase 1 are allowed during the first 14 days and all later stages as well. In phase 2 you add more options (along with the ones in phase 1), and in phase 3 you can eat almost anything in moderation, while continuing portion control and other healthy habits.

Beans and legumes In moderation Phase 1
Condiments and sauces Allowed
Phase 1
Dairy Allowed
Phase 1 (low-fat)
Sugar-free drinks Allowed Phase 1
Sugar-sweetened beverages Not allowed Not allowed
Alcoholic drinks Allowed
Phase 2
Eggs Allowed Phase 1
Fish and seafood Allowed Phase 1
Fruits In moderation Phase 2
Grains and starches In moderation Phase 2
Herbs and spices Allowed Phase 1
Meat and poultry Allowed Phase 1 (low-fat)
Nuts and seeds Allowed Phase 1
Oils and fats Allowed Phase 1
Processed foods Not allowed Not allowed
Sugar-free sweeteners Allowed Phase 1
Natural sweeteners Allowed
Not allowed
White and brown sugars Not allowed Not allowed
Starchy vegetables In moderation Phase 2
Non-starchy vegetables Allowed Phase 1


As you can see, there are a lot of similarities between phase 1 and keto. You can also consume much of the same things from phase 2 in a keto diet as long as you keep your carb intake under control.

If you don’t know whether a food is keto-friendly or not, you can check this keto-approved food list to ensure you are on the right path.


How much does South Beach cost compared to keto?

The costs for each diet are very similar. It all depends on the type of food that you buy. For example, if you are getting organic or grain-free meat, then your grocery bill is going to be bigger.

Also, carb options tend to be cheaper than fats and protein, which makes both diets somewhat expensive compared to a more carb-based one.

However, you can lower your grocery bill by shopping locally and buying produce that's in season.


Which one is a better diet, keto or South Beach?

Both the keto and South Beach diets can be excellent healthy options for weight loss. There are just a couple of things to consider to follow the healthiest version.

When it comes to the ketogenic diet, remember to cut back on saturated fats (like butter, sausages, bacon, and cured meats) since they can be unhealthy for your heart. Focus more on healthy fats like avocado, nuts, seeds, and oils.

Additionally, to help provide your body with several nutrients, make sure to eat at least three different color veggies during the day.

Finally, the South Beach plan places a great emphasis on having lean protein. Although in keto you have a higher fat intake, try to maintain this philosophy as well. Rather make up your fats with the healthy fats we mentioned above.


Final thoughts

Both are great options when you want to lose weight. For those that don’t want to keep a carb count during the day, you might want to consider the South Beach approach.

On the other hand, if you prefer to have a more controlled carb intake but higher fat content, you might want to go with the ketogenic diet.