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Special Diets for Weight Loss: A Comprehensive Guide

Reviewed by: HU Medical Review Board | Last reviewed: May 2023

There are countless diets that can help with weight loss. Each has unique goals and guidelines. Some may be right for you, while others may not be. And some are healthier than others. Each person on a weight loss journey has different health goals, so finding the right diet that works for those goals is key.

Several diets have gained lots of attention in recent years. Here, we break down some of the more well-known diets to understand how they work and how well they can help you achieve and maintain weight loss.

Keto diet

The keto diet, short for the ketogenic diet, is a low-carbohydrate (carb), high-fat, and moderate-protein diet. Its main goal is to shift the body's metabolism into a state called ketosis. During ketosis, the body burns fat for fuel instead of carbs.1

A typical keto diet consists of:1

  • 70 to 80 percent fats
  • 20 percent proteins
  • 5 to 10 percent carbs

When you limit carbs to 5 to 10 percent of your diet – under 50 grams per day – your body produces ketones. It then uses the ketones as an alternative energy source.1

The keto diet prioritizes fat and protein. It restricts carbs like whole grains (bread, pasta, oats, cereal) and certain fruits and vegetables. The types of foods eaten on the keto diet are:1

  • Meat and fish
  • Eggs
  • Avocados
  • Nuts and seeds
  • Oils, such as olive oil
  • Olives
  • Cheese
  • Butter and cream

The keto diet has been shown to be effective for weight loss. It has also been shown to be helpful in treating the following:1

  • Epilepsy – The keto diet has been shown to reduce seizures in some people, especially in children.
  • Type 2 diabetes – Keto can help those with type 2 diabetes lose weight and also manage blood sugar levels.
  • Heart disease – Keto may help lower blood pressure and help improve HDL cholesterol (the “good” kind of cholesterol).
  • Inflammation – Keto can help reduce inflammation in the body.

While the keto diet can help people lose weight, it can be extremely hard to stick to. Also, it restricts many nutritious foods like certain fruits and vegetables because they are carbs. This is concerning because these foods provide essential vitamins and minerals that help keep your body healthy.1

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Low-carb diet

A low-carb diet involves reducing carbohydrate intake while maintaining a moderate protein and fat intake. While similar to the keto diet, it is not quite so strict.2

This diet includes mostly:2

  • Lean proteins
  • Healthy fats
  • Non-starchy vegetables like spinach and asparagus
  • Low-carb fruits like berries

The diet limits grains, legumes (beans, peas, lentils), and starchy vegetables like corn and potatoes.2

Low-carb diets can help people lose weight while also helping to:2

  • Control blood sugar levels
  • Improve blood pressure
  • Increase HDL cholesterol

Many studies have shown that low-carb diets can lead to weight loss. However, for many, this kind of diet is not sustainable in the long term. Like keto, low-carb diets can be hard to stick to. Once weight loss goals have been achieved, experts recommend slowly adding healthy, complex carbs back into your diet for sustainable weight management.3

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Paleo diet

The paleo diet, also known as the "caveman diet," mimics the eating patterns of our ancestors during the Paleolithic era. This time in history lasted from about 2.5 million years ago to 10,000 BC. Put simply, the paleo diet consists of whatever foods humans used to eat millions of years ago.4

The paleo diet emphasizes whole, unprocessed foods, such as:4

  • Lean meats
  • Fish
  • Eggs
  • Fruits
  • Vegetables
  • Nuts and seeds

Foods that are excluded from a paleo diet include:4

  • Grains
  • Legumes
  • Dairy
  • Refined and added sugars
  • All processed foods

Because it eliminates all processed foods, the paleo diet can help people lose weight. It may also help improve:4

  • Blood pressure
  • Cholesterol levels
  • Triglyceride levels
  • Inflammation

Some studies have linked the paleo diet with a lower risk of heart disease. But research is ongoing and more studies are needed. And the paleo diet cuts out several nutrient- and fiber-rich foods like legumes and whole grains.4

Mediterranean diet

The Mediterranean diet is inspired by the traditional diet of Mediterranean countries. It focuses on whole or plant-based foods such as fruits, vegetables, whole grains, legumes, fish, and olive oil. It limits processed foods, red meat, and sweets.5,6

For many people, the Mediterranean diet is a more sustainable diet than other diets. Eating this way means eating:5,6

  • Whole fruit and vegetables
  • Whole, unprocessed grains like whole wheat bread and brown rice
  • Healthy fats like avocados, nuts, and seeds
  • Lean meats like poultry and fish
  • Olive oil
  • Moderate amounts of dairy like cheese and yogurt
  • Moderate amounts of wine

The Mediterranean diet focuses on a more flexible, moderate way of eating rather than having strict rules. That said, it does limit:5,6

  • Processed foods
  • Red meat
  • Sweets
  • Butter
  • Added sugars

The Mediterranean diet is probably the most extensively studied diet for its many health benefits. Research shows that this diet can lower your risk of heart disease, heart attack, and stroke. It has also been shown to:5,6

  • Help you lose weight
  • Improve digestion and gut health
  • Regulate blood sugar levels
  • Lower blood pressure
  • Help with cholesterol levels
  • Keep your brain healthy
  • Lower your risk of certain cancers
  • Help you to live longer

Vegan diet

A vegan diet eliminates all animal products. It includes only plant-based foods such as fruits, vegetables, legumes, grains, nuts, and seeds. It is low in saturated fat and high in fiber, making it potentially helpful for weight loss.7

A person who follows a vegan diet does not eat:7

  • Meat
  • Seafood
  • Eggs
  • Dairy

A 2019 review found that plant-based diets, including vegan diets, were linked to a reduced risk of type 2 diabetes. Other research indicates that a vegan diet also may help prevent certain diseases, such as:8

  • Obesity
  • High blood pressure
  • Heart disease
  • Certain types of cancer

Intermittent fasting

Intermittent fasting involves cycling between periods of not eating (fasting) and eating. Rather than focusing on what you eat, intermittent fasting focuses on when you eat.9

Popular methods include:9

  • 16:8 method – fasting for 16 hours and restricting eating to an 8-hour window every day
  • 5:2 method – eating normally for 5 days, then 2 days where you do not go over 600 calories
  • Alternate-day fasting – fasting every other day

Intermittent fasting has gained attention in recent years for its potential benefits for weight loss. A 2022 review of several studies found that intermittent fasting was effective in reducing:10

  • Body weight
  • Waist circumference
  • Fat mass

In addition to weight loss, intermittent fasting has been shown to help with type 2 diabetes and inflammatory bowel disease. In fact, some studies have shown that when people with type 2 diabetes eat this way under a healthcare provider’s supervision, it has reversed the need for insulin therapy.9

Intermittent fasting also may be beneficial for:9

  • Brain health
  • Heart health
  • Tissue health
  • Improved physical fitness

How does intermittent fasting help with weight loss? After several hours of fasting, the body uses up its stores of sugar to burn energy and then switches to burning fat. However, results vary widely per person.9

Intermittent fasting is not right for everyone. People who should avoid it include:9

  • People who are pregnant or breastfeeding
  • Children and teens under 18 years old
  • People with type 1 diabetes and need to take insulin
  • People with a history of eating disorders

Choosing a diet that works for you

While each diet mentioned above has shown promise for weight loss, results may vary based on:

  • Age
  • Metabolism
  • How well you stick to the diet
  • Underlying health conditions
  • Overall calorie intake

Diets that are overly restrictive or eliminate entire food groups may be challenging to maintain in the long run. They can potentially lead to nutrient deficiencies if not properly planned. Diets can also be triggering for some people with a history of disordered eating.1,3,9

Also note that all diets have the potential to cause side effects. Side effects can vary depending on the specific diet. When deciding on a diet, consider how sustainable it will be, what the possible side effects are, and what effect it may have on your overall health.

Talk with your healthcare provider

If you are starting a weight loss journey, talk to your doctor or a registered dietitian. They can give you personalized guidance and support. Remember, sustainable weight loss is a gradual process that requires a combination of healthy eating, regular physical activity, and lifestyle changes.