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Keto Vs. South Beach: Which Diet Is Better?


If you want to improve your health, look first to nutrition. The right diet can help you lose weight, boost your energy, improve your appearance, and lower your risk of chronic disease.

What’s the right diet for you? That depends on your health goals and food proclivities.

Today you’ll be learning about two popular weight loss diets: the keto diet and the South Beach Diet. By the end of the article, you should have enough info to make up your mind about them.

What Is the Keto Diet?

The ketogenic (or “keto) diet is a low-carb high-fat diet that has you consuming about 60% of your calories from fat, 30% from protein, and 10% from carbohydrates. Keeping fat, protein and carbs in these ratios eases you into a unique metabolic state called ketosis.

When you’re in ketosis, your cells burn (or beta-oxidize) fat to produce molecules called ketones. In turn, these ketones provide energy to power your cells, especially your brain cells[*].

Normally, your cells rely on sugar (glucose) for energy. But in a state of ketosis, your body gets off the blood sugar roller coaster and boards the smooth and steady fat train.

Carb restriction is the key to this fat-burning state. That’s because when you keep carb intake low, your blood sugar stays low. And low blood sugar means less insulin (your blood sugar boss hormone) gets released[*].

Think of low insulin as the ketosis bat signal. Less insulin, more fat burning.

To confirm you’re on track with keto, you can measure ketone levels using blood or urine test strips. This ability to measure progress with a specific biomarker is unique to the keto diet.

Research has shown that the keto diet can help with weight loss, diabetes, cravings, brain health, inflammation, and more[*][*][*][*][*].

Keto-Friendly Foods To Eat:

  • Healthy fats like butter, lard, olive oil, coconut oil, avocado oil, heavy cream, and macadamia nut oil
  • Nuts like almonds, pistachios, walnuts, cashews, and macadamia nuts
  • Proteins like animal protein, fatty fish, whey protein, and vegan protein powder
  • Non starchy vegetables that are high in fiber and low in carbs
  • A limited amount of low-carb fruits like berries, lemons, and limes

Foods To Avoid On Keto:

  • High-carb foods like grains, starchy vegetables, and most fruits
  • Anything with added sugar
  • Refined foods, including industrial seed oils

For a full list of keto-friendly foods, see this comprehensive ketogenic diet food list.

What Is The South Beach Diet?

In 2003, cardiologist Arthur Agatston authored “The South Beach Diet: The Delicious, Doctor-Designed, Foolproof Plan for Fast and Healthy Weight Loss.” In the book, Agatston sketched the rules of the South Beach Diet, making a number of health claims (mostly to do with weight loss) along the way.

The South Beach Diet plan restricts processed carbs (sugar, for instance), but it’s not technically a low-carb diet. The overall focus is on lean protein, monounsaturated and polyunsaturated fats, and low-glycemic, or “good,” carbs.

Low-glycemic, in case you were wondering, refers to the glycemic index — a measure of how much a given food spikes blood sugar. Sugar and processed carbs tend to have a high glycemic index, while fibrous vegetables and grains tend to be lower on the scale.

But here’s the thing. Different people have different blood sugar responses to the same food, which makes the glycemic index measure difficult to trust[*].

South Beach Diet Phases

There are three phases of the South Beach Diet, each less restrictive than the next.

  • Phase 1: Eat lean protein, monounsaturated and polyunsaturated (but not saturated) fats, nuts, avocados, and low-carb vegetables. Nearly all carbs are eliminated, including fruit juice, alcohol, whole grains, and fruit. Phase 1 lasts two weeks.
  • Phase 2: Continue with foods from Phase 1 and reintroduce whole grains, starchy vegetables, and fruits. Stay in Phase 2 until you hit your weight loss target.
  • Phase 3: This “maintenance phase” allows all foods in moderation. You’re advised, however, to stick with the basic Phase 2 setup.

What Do Keto and South Beach Have In Common?

Both keto and South Beach are weight loss diets, and have at least two common strategies to get you there. Read on.

#1: No sugar

High sugar consumption is a big cause of obesity in America. All those sugary sodas, sports drinks, and fruit juices are making people fat[*].

Added sugar, you’ll want to know, is forbidden on both keto and for phases 1 and 2 of the South Beach Diet. Phase 3 is more liberal, and allows the occasional sugar hit.

#2: Moderate protein

Protein is not an optional nutrient. You need protein to maintain muscle, create neurotransmitters, and much more.

Low-protein diets, it’s been shown, are linked to the age-related muscle decline known as sarcopenia[*]. Sarcopenia is bad news. Lower quality of life, less functional strength, frailty, and so on.

Both keto and South Beach are fairly high-protein diets. On keto, for instance, you eat about 30% of your daily calories from protein. On a 2,000 calorie diet, that’s about 150 grams.

What’s the Difference Between Keto and South Beach?

You just learned the common features of keto and South Beach. Now you’ll discover how these diets differ.

#1: South beach isn’t truly low-carb

On the keto plan, you limit carbs to under 10% of calories. This prevents blood sugar and insulin from rising, and keeps you in ketosis.

The South Beach diet, on the other hand, doesn’t have clear boundaries on carbs. The first phase is fairly low-carb, but as you progress later in the diet, more carbs are reintroduced.

For instance, South Beach allows whole grains, root vegetables, legumes, and fruits for most of the program. Some of these foods, like sweet potatoes, are nutrient dense. Others, like pasta, bread and rice are not.

#2: South Beach sanctions grains

Whole grains are controversial. Some say they’re healthy because they contain fiber. Others argue that grains don’t belong in a nutritious diet.

The anti-grain camp makes a strong case. Whole wheat, for instance, contains:

  • Gluten: A wheat protein that provokes intestinal damage. This is true even in those without celiac disease, a condition marked by gluten autoimmunity[*].
  • Wheat germ agglutinin (WGA): Another wheat protein linked to gut disorders[*].
  • Lectins: Plant proteins that can damage the intestines and create autoimmune issues[*].
  • Phytic acid: A plant-based compound that prevents nutrients from being absorbed.

Ancestral approaches like keto and paleo, however, don’t allow grains.

#3: Quality of evidence

Both keto and South Beach are presented as weight loss diets. What does the published evidence say?

For South Beach, not much. One trial found that 20 overweight and obese people lost about 11 pounds after 12 weeks of South Beach dieting, but there was no control group, so the results are on shaky ground[*].

Another review found that 67% of the nutrition facts from the South Beach book “may not be supported by the peer-reviewed literature”[*]. That’s most of the book!

The keto diet, conversely, is not based on a bestselling book—but rather on published data that’s been accumulating since the 1920s. Scores of randomized controlled trials suggest keto can help with weight loss, hunger management, cognitive enhancement, diabetes reversal, and much more[*][*][*][*].

#4: Keto allows saturated fat

Keto allows saturated fats like coconut oil and butter, but limits polyunsaturated vegetable oils like soybean and peanut oil. The South Beach meal plan takes the opposite stance: Sat fat bad, veggie oils good.

Saturated fat, to start there, has been vilified as a risk factor for heart disease, but the data suggest otherwise. In fact, two recent reviews analyzed dozens of studies and found no link between saturated fat consumption and heart disease[*][*].

High omega 6 vegetable oils, consumed in excess, are a different story. In fact, researchers believe the inflammatory effects of vegetable oil consumption are partly responsible for the American obesity problem[*][*].

Cooking with veggie oils is even worse. When heated, these fats form oxidized lipids—nasty compounds that accelerate the progression of heart disease[*]. Saturated fat, however, is safe for cooking[*].

Choosing Between Keto and South Beach

Both keto and South Beach improve on the Standard American Diet. Cutting out sugar and processed foods goes a long way towards boosting your health.

The main difference between the keto and South Beach? Carbs and fats.

While South Beach has you cutting carbs for two weeks, it’s not low-carb like keto. You won’t be entering ketosis — the metabolic state linked to all those health benefits — on South Beach.

South Beach also favors vegetable oils over saturated fats. This is troubling because veggie oils are linked to inflammation, obesity, and heart disease.

Keto works great for many folks, but not everyone. Here’s a suggestion: If you want carbs in your life, skip the South Beach Diet and consider a Paleo or Medittaranean diet — both whole foods approaches compatible with healthy eating.

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