Protein-Sparing Modified Fasting versus the Carnivore Diet - What's the difference?

Protein-Sparing Modified Fasting (PSMF) and the Carnivore Diet are two dietary approaches that have gained popularity for different reasons. Let's compare them in terms of their principles, benefits, and potential risks.

What is PSMF?

A Protein-Sparing Modified Fast (PSMF) is a specialized, medically supervised diet that is designed to promote rapid weight loss in individuals who are significantly overweight or obese. It is a very low-calorie diet that focuses primarily on high-quality protein intake, with minimal consumption of carbohydrates and fats. The goal of a PSMF is to provide essential amino acids to preserve lean muscle mass while inducing a state of ketosis, where the body primarily burns fat for energy.

Here are the key principles of a Protein-Sparing Modified Fast:

1. High Protein Intake: The diet emphasizes the consumption of lean protein sources such as chicken, turkey, fish, and low-fat dairy products. Protein intake is typically the main source of calories during a PSMF.
2. Limited Carbohydrates and Fats: Carbohydrates and fats are restricted to minimal levels, usually less than 50 grams per day. This restriction forces the body to rely on protein and stored body fat for energy.
3. Caloric Restriction: The daily caloric intake during a PSMF is very low, often ranging from 500 to 800 calories per day. This drastic calorie reduction creates a significant calorie deficit, leading to rapid weight loss.
4. Supervised by Healthcare Professionals: PSMF should be done under the supervision of healthcare professionals, such as doctors or registered dietitians, due to its extreme nature and potential health risks.
5. Short-Term Duration: PSMF is not meant to be followed for an extended period. It is typically recommended for short-term use, lasting a few weeks to a few months, and is often used as a preparation for weight loss surgery.
6. Nutritional Supplements: Since the diet is severely restricted in calories and food variety, individuals on a PSMF are often prescribed vitamin and mineral supplements to prevent nutrient deficiencies.

It's important to note that a PSMF is not suitable for everyone and should only be considered under medical supervision. Rapid weight loss diets, including PSMF, can pose health risks, and long-term weight maintenance often requires a more sustainable and balanced approach to eating and physical activity. Individuals interested in losing weight should consult healthcare professionals or registered dietitians to develop a safe and personalized weight loss plan.

Example of a PSMF day:

Breakfast: 1 cup liquid egg whites, scrambled with 1 teaspoon hot sauce

Total: 133 calories, 0 grams of carbs, 0 grams of fat and 32 grams of protein

Lunch: 1 can of chunk tuna packed in water with 11 olives and fat free salad dressing and ½ tablespoon olive oil

Total: 198 calories, 3 grams of carbs, 12 grams of fat and 22 grams of protein

Dinner: 1 cup (40 grams) mixed salad greens with 175 g grilled chicken breast with 1 tablespoon olive oil

Total: 179 calories, 2 grams of carbs, 20 grams of fat and 55 grams of protein

Total for Day #1 - 749 calories, 4 grams of carbs, 31 grams of fat, and 109 grams of protein

What is the Carnivore Diet

The Carnivore Diet is an extreme dietary approach that involves consuming exclusively animal products, primarily meat, fish, and animal fats, while completely excluding plant-based foods. This means individuals following the Carnivore Diet eat meat, poultry, fish, eggs, and animal-derived fats like butter and lard. The diet excludes all forms of plant foods, including fruits, vegetables, grains, legumes, nuts, seeds, and plant-based oils.

Key principles of the Carnivore Diet include:

1. Animal Products Only: The diet revolves around the consumption of animal products to fulfill all nutritional needs.
2. Zero Carbohydrates and Fiber: The Carnivore Diet eliminates all sources of carbohydrates, including sugars and fiber. This restriction puts the body in a state of ketosis, where it burns fat for fuel instead of carbohydrates.
3. High Fat and Moderate Protein: While the primary focus is on animal fats and proteins, the specific ratio can vary based on individual preferences and goals.
4. No Plant-Based Foods: All plant foods, even those traditionally considered healthy, are strictly avoided.

Proponents of the Carnivore Diet claim various benefits, including weight loss, improved mental clarity, reduced inflammation, and relief from certain health conditions. However, it's important to note that this diet is highly controversial and lacks substantial scientific backing.

Potential Benefits:

1. Simplicity: The diet is straightforward, as there's no need to count carbohydrates or worry about food combinations.
2. Potential for Weight Loss: Some individuals may experience weight loss due to the drastic reduction in calorie intake and the body's shift into ketosis.
3. Elimination Diet: For people with severe food allergies or intolerances, the Carnivore Diet can serve as an elimination diet to identify specific triggers.

Potential Risks:

1. Nutrient Deficiencies: The diet lacks many essential nutrients found in plant foods, potentially leading to deficiencies in vitamins, minerals, and fiber.
2. Digestive Issues: Some people may experience digestive problems such as constipation due to the absence of fiber.
3. Long-Term Health Risks: The long-term health effects of an exclusively animal-based diet are not well understood, and there are concerns about increased risks of heart disease, certain cancers, and other health issues.
4. Environmental Impact: The Carnivore Diet's heavy reliance on animal products raises concerns about its environmental impact, including greenhouse gas emissions and land use.

As with any extreme diet, individuals considering the Carnivore Diet should consult with healthcare professionals or registered dietitians to assess the potential risks and benefits in the context of their overall health and nutritional needs.

Types of Carnivore Diets

There are different types of carnivore diets. Below are some of the different versions of this diet.

1. Traditional Carnivore Diet: This version of the diet includes only animal products such as meat, fish, eggs, and animal fats. It excludes all plant foods, including fruits, vegetables, grains, legumes, nuts, and seeds.
2. All-Meat Diet: This variation strictly consists of meat and animal products. It excludes other animal-derived foods like eggs and dairy. Some proponents argue that this is the purest form of the carnivore diet. Many people with autoimmune problems like to start here until there symptoms resolve and then move into a less strict version of the carnivore diet.
3. Zero-Carb Carnivore Diet: While all versions of the carnivore diet are low in carbohydrates, the zero-carb carnivore diet is particularly strict about eliminating any trace of carbohydrates. This means avoiding even small amounts of carbohydrates found in certain animal products like liver and dairy.
4. Raw Carnivore Diet: Followers of this variation consume raw, uncooked animal products. This includes raw meat, raw eggs, and sometimes raw dairy. Proponents claim that cooking destroys essential nutrients and enzymes, which are preserved in raw foods.
5. Dairy-Based Carnivore Diet: This version allows for the consumption of animal products derived from dairy, such as cheese, butter, and heavy cream. While dairy is animal-derived, it contains lactose, a carbohydrate, so it technically deviates from the strictest zero-carb approach.
6. Organ-Based Carnivore Diet: In this variation, emphasis is placed on consuming organ meats, such as liver, kidney, and heart, in addition to muscle meats. Organ meats are nutrient-dense and provide essential vitamins and minerals.
7. Seasonal Carnivore Diet: Some individuals follow a carnivore diet seasonally, incorporating plant-based foods during certain times of the year, such as fruits and berries in the summer. This approach allows for some flexibility and variety in the diet.

Example of a Carnivore day:

Here is an example of a more or less traditional carnivore diet:

Breakfast: 3 large eggs with 2 slices (44 grams) of bacon

Total: 295 calories, 1 grams of carbs, 20 grams of fat and 26 grams of protein

Lunch: 4 oz Bacon-Wrapped pork loin (recipe to come!) with 2 oz blue cheese sauce (recipe to come!)

Total: 295 calories, 3 grams of carbs, 23 grams of fat and 19 grams of protein

Dinner: 150 grams of Ribeye cooked in 2 tablespoon of butter

Total: 629 calories, 0 grams of carbs, 56 grams of fat and 32 grams of protein

Total for Day #1 - 1219 calories, 4 grams of carbs, 99 grams of fat, and 76 grams of protein

How to Calculate your Macros

Regardless of either the Protein-Sparing Modified Fasting or the Carnivore diet, you will want to calculate how many calories, carbs, fats, and protein your body needs.

Depending on your goals (ie. weight loss, increased strength, or maintaining weight), you will need to calculate how much to eat on each of these diets as they differ in their requirements.

Here is a General Calculation for the PSMF diet

For Women:

If you want to follow a PSMF, the general rule is that women who are 5 feet tall start around 80-90g protein then add 5g protein per inch of height.

For example, I am 5'8 so I will need 80 g + (5 x 8) = 120 grams of protein. As for carbs, you want to keep your carbs as close to 10 grams (this is TOTAL grams of carbs and not net grams) with a max of 20 grams. As for fat, you will want to keep your fat grams to 30 grams a day.

For Men:

Since most men have more muscle mass than women due to their higher levels of testosterone, men should start their calculations with 100 grams of protein and add 5 grams of protein for every inch.

For example, a male measuring 6 feet tall would need 100 g + (5 x 12) = 160 grams of protein. As for carbs, you want to keep your carbs as close to 10 grams (this is TOTAL grams of carbs and not net grams) with a max of 20 grams. As for fat, you will want to keep your fat grams to 30 grams a day.

You can use Maria Emmerich's PSMF calculator to find your individual macros.

How do I calculate my macros for a Carnivore diet?

As for calculating your protein macros if you want to follow a carnivore diet, you will aim for around 0.8-1g of protein per pound of goal body weight if you're sedentary and 1-1.2g of protein per pound of goal body weight if you're training hard or trying to gain muscle.

As for your fat, you will need around 0.8g-1g of fat per 1lb of body weight. While it may seem a little less than protein, that's because fat has 9 calories per gram compared to only 4 calories per gram in protein. Fat is extremely energy-dense.

However, if you're working with an autoimmune condition or feel low energy with your current fat intake, you can always add some extra saturated fat to your diet and lower protein intake.

As for carbs, the aim is to stay as close to zero as possible. This can be very challenging as even the highest protein sources (such as shellfish), spices, and low carb sauces add some carbs to your recipe.

Here is a General Calculation for the Carnivore diet

So, all you have to do to keep this really simple is to take your goal weight and aim for that number in grams of protein and fat. For example, if your goal weight is 130 lbs, you will want to aim for 130 grams of protein as well as 130 grams of fat and as close to zero carbs as possible. Simple, right?!

Summary of PSMF versus Carnivore Diet

Principles:

1. High Protein Intake: PSMF involves consuming a very low-calorie diet with a focus on high-quality protein sources. The goal is to provide essential amino acids to preserve lean muscle mass while promoting fat loss.
2. Limited Carbohydrates and Fats: Carbohydrates and fats are restricted to minimal levels, ensuring the body primarily relies on protein for energy.
3. Medically Supervised: PSMF is often conducted under medical supervision due to its extreme nature, and it's typically recommended for people with obesity or those preparing for surgery.

Benefits:

1. Rapid Weight Loss: PSMF can lead to rapid weight loss due to the significant calorie deficit.
2. Preservation of Lean Muscle Mass: High protein intake helps preserve muscle mass during the weight loss process.
3. Metabolic Reset: Some proponents suggest that PSMF can help reset the metabolism and improve insulin sensitivity.

Risks:

1. Nutrient Deficiency: Due to the limited variety of foods, there's a risk of nutrient deficiencies.
2. Muscle Loss: Despite the high protein intake, extended periods of very low-calorie intake can lead to muscle loss.
3. Not Sustainable Long-Term: PSMF is not a sustainable long-term diet and should only be done under medical supervision for short periods.

Carnivore Diet:

Principles:

1. Animal Products Only: The Carnivore Diet involves exclusively consuming animal products, primarily meat, fish, and animal fats. It excludes all plant-based foods, including fruits, vegetables, grains, and legumes.
2. Elimination of Carbohydrates and Fiber: This diet eliminates carbohydrates and fiber entirely, relying solely on animal-derived nutrients.

Benefits:

1. Simplicity: The diet is straightforward as it involves eating only animal products, which some people find easy to follow.
2. Potential for Weight Loss: Due to the absence of carbohydrates, the body enters a state of ketosis, which may lead to weight loss for some individuals.
3. Digestive Issues Improvement: Some proponents claim that adopting a Carnivore Diet has helped them alleviate digestive issues like bloating and gas.

Risks:

1. Nutrient Imbalance: The diet lacks a variety of nutrients found in plant-based foods, potentially leading to nutrient imbalances and deficiencies.
2. Digestive Problems: Some individuals may experience digestive problems, such as constipation, due to the lack of fiber in the diet.
3. Lack of Long-Term Studies: There is a lack of long-term research on the safety and effectiveness of the Carnivore Diet.

Conclusion:

Both PSMF and the Carnivore Diet have their unique principles, potential benefits, and risks. It's essential for individuals to consult healthcare professionals or registered dietitians before attempting any extreme diet. Long-term sustainability, balanced nutrition, and overall health should always be the primary considerations when choosing a dietary approach.

How to implement the PSMF with a Carnivore Diet?

If you are looking to shed weight, combining a PSMF with a Carnivore diet might just be the trick! I decided to try this to see not only how I felt but also how my weight was affected.

Since I work full time and like to exercise and lift weights, I chose to pick the diet I would use for the day based on my energy requirement for that given day. Since I run and lift weights on Tuesday, Thursday, Saturday, and Sunday, I chose to use the Carnivore diet for those days since my calorie expenditure is higher on those days. For the other days, I used the lower-calorie PSMF.

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