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How To Do a Protein Sparing Modified Fast

If you are trying to drop body fat in a hurry then maybe you have read about a protein sparing modified fast, or PSMF. If you haven't heard about it then today we are going to dive into the basics about it and why it would or wouldn't be a valuable tool for your needs.
Josh Koop
February 19, 2020

If you are trying to drop body fat in a hurry then maybe you have read about a protein sparing modified fast, or PSMF. If you haven't heard about it then today we are going to dive into the basics about it and why it would or wouldn't be a valuable tool for your needs.

How To Do a Protein Sparing Modified Fast? The best way is to seek out Lyle McDonald's Rapid Fat Loss Handbook, this is due in large part to it being a low fat and carb "managed" crash diet. While people hear bad things about "crash" diets this book is all about how you can drop body fat fast in a window.

As a note, this style and approach isn't for the faint of heart and is one where you need to measure and monitor everything each day that you eat and drink. You should look at purchasing the handbook, reading it slowly and with an eye to understanding how and why it works, and how long is your attempt planning to be.

As always with health related topics you shuold discuss with your physician any health related concerns and be honest with them.

What is a Protein Sparing Modified Fast Diet (PSMF)?

At the core a protein sparing modified fast diet is all about making sure you consume adequate protein so you don't lose muscle mass while cutting short the energy supply so your body focuses on using your body fat for the missing fuel.

For most people this would mean 120-200g of protein being eaten while sticking to a minimal amount of fats from the diet, typically this approach to rapid fat loss will include fish oil with high levels of DHA/EPA to ensure you keep levels up.

As long as you keep the levels of protein up your body will continue to spare the body and muscle proteins leading to a better level of fat loss, though this is meant to be done in short cycles and not intended to be run for months at a time which is why I feel it is a "Crash diet" in terms of fast measurable results.

Foods rich in protein, including cheese, eggs, fish, lamb, beef and chicken. How To Do a Protein Sparing Modified Fast
Foods rich in protein, including cheese, eggs, fish, lamb, beef and chicken.

What is the Purpose of a PSMF?

Basically to produce high speed fat-loss results on a short duration timetable. This is an exceptional way to lean down fast for the wedding coming up, photo shoot, or to help kick a fat-loss overall diet approach off and give you some hope into the start of the diet.

A PSMF approach is a temporary diet meant to kick-start rapid weight loss in people who are already severely obese. Though it can also be used for people that are very lean, in-shape and need to lose those last few pounds be it stubborn body fat or just the last few pounds when trying to reach their goal weight.

Example Macro-Nutrient Breakdown

Lets dig in to show an example of the breakdown for a somewhat "normal" male. Below is an example macro breakdown of a 200lb male with 10% body fat which would translate into 180lbs lean mass.

  • Carbohydrate - 15-20 grams
  • Fat - 15-20 grams (Include at least 10 grams of fish oil in that total)
  • Protein - 1.5 grams-2 grams of PROTEIN per pond of lean mass so 270-360gms.

As you can see your daily caloric total will probably be 50-60% of what you are normally used to eating. My normal caloric intake will vary around 1800-2300, whereas on a PSMF it will be around 1200-1300.

What to Eat on a Protein Sparing Modified Fast?

You want to aim to eat very protein high and fat low foods, as this will help ensure you stay satiated. It is very hard to eat 200g of chicken breast as that is almost 2 pounds if measured out.

Recommended Supplements For a PSMF

Fish Oil - The PSMF diet lacks in essential fatty acids(also know as EFA’s), so a supplement will be needed. Most recommend up to 10,000mg/day. This is essential for this diet so don't forget these. These are the most important and I use these from Coromega cause I love the taste and they arent pills so easy to carry in my lunches.

A Multivitamin/Multi-mineral supplement: The lack of fruit combined with limited vegetables could lead to vitamin deficiencies especially the longer you are on the diet.

Play it safe and take a multivitamin/mineral supplement when following a PSMF. I prefer KetoLabs multivitamins, take a look as they are aimed at helping Ketogenic dieters so they contain a different assortment of vitamins.

ECA stack (Ephedrine, Caffeine, Aspirin) – Quite Optional but many find it can be essential for blunting hunger, giving you tons of energy and well lets be honest, the most research “fat burner” in history.

I take Modern Man V3 which is really just Caffeine but it has helped cut down my soda consumption.

SODIUM - As most ketogenic and carnivore dieters will know, if you feel like crap, get a few grams in from chicken or beef bullion powder and it will help works wonders! I personally use HiLyte as it is a squeezable liquid I can add to my water.

Protein Powder - Many people will have no issues with protein powders and find them helpful and sometimes necessary to hit their daily protein total.

The only downside is that they are not very satiating so if you want to use some then try to get micellar casein which will have a better chance of filling you up versus standard whey.

For a PSMF, casein proteins are better than traditional whey because it digests much slower while being more filling.

Is PSMF Safe?

The protein sparing modified fast has been studied by the NIH(source) and has been proven to be safe and effective for rapid weight loss. They studied 12 subjects who were evaluated in the Obesity Management Program at the Cleveland Clinic and went through refeeding time.

Results show that the PSMF diet can be used as an effective and safe method in the outpatient setting for rapid weight loss in adolescents with severe obesity

The Protein-Sparing Modified Fast Diet

PSMF Tips & Tricks

Intermittent Fast or Time Restrict Your Feeding - This may seem or appear obvious, since you are only consuming a small amount of calories you’ll be better off eating them all in one sitting or two.

Eat Real Food - To feel full and satiated you need to focus on real foods which require chewing, avoid protein shakes and liquid foods as they have less ability to help you feel full.

Plan Your Refeed - A refeed to the tune of 1.5 to 2 grams of carbohydrate per pound of lean mass is about typical at the end of the fast. By taking the time and planning ahead you will avoid the “eating everything in sight” effect that often accompanies completing exceptionally strict diets, choose things wisely to keep the gains.

Use Spices, Salsas, and Mustard: Most of these are zero calorie and can help you to add a ton of flavor. The plan should be to cycle them day by day to make the foods more interesting.

Reviews From Outside Sources

User Review

I followed the protocol set forth in the Rapid Fat Loss Handbook in my 40s and got down to a size 2 from a size 8. I seriously had the body of a 20 something year old young woman! Combined with weight or resistance training, you CAN’T FAIL if you follow this program! It’s tough, takes discipline but totally worth it. I highly recommend this book to anyone that wants to really lower their body fat percentage!

User Reviews From Body Recomposition Website

Final Thoughts on How To Do a Protein Sparing Modified Fast

I hope this crash course on the Protein Sparing Modified Fast has helped get you a good solid base understanding of what it is and why it helps with fat loss on a quick plan.

Leave a comment below if I missed something as I am not a super expert just sharing what is working for me and has worked for me, this means I definitely may not know something awesome you can share!

If you read this far you are amazing! I would love to hear from you in the comments below if I helped you gain knowledge and useful information, additionally I would like to know if I got anything incorrect that you believe should be researched more and updated. As always to get the word out please join our new Carnivore Rx group on Facebook and share this out on social media!

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