What is the PSMF Diet? A Practical Guide to the Protein Sparing Modified Fast

What is PSMF? A Practical Guide to the Protein Sparing Modified Fast

The PSMF Diet or Protein sparing modified fast is a very low calorie, low carbohydrate and high protein diet designed for rapid weight loss without causing muscle loss.

It is a diet that mimics fasting in it’s results except that you are still eating food and you are ‘sparing’ your muscle. That’s why the long name! If you think of it as a low calorie, low fat, low carb diet, it’s easier to understand then.

What I didn’t know is that this low-calorie diet has been around since the 1970’s and is typically used in hospitals and other medically supervised settings particularly with obese patients before bariatric surgery. It is designed to reduce body fat quickly while maintaining lean body mass, in other words it ‘spares’ your muscle.

food collage for PSMF lean proteins

It is not a long term diet and anyone following this very low calorie diet for any length of time should be doing so under the supervision of healthcare providers. Even under medical supervision, obese patients are kept on the PSMF diet for only up to 6 months.

So why am I even talking about it then?

Because there is a safe way that we can make use of the protein sparing principles to accelerate fat loss or break a stall when doing Keto. My issue is that lately in the Keto space it has become the new buzz word and there is so much hype.  I think people should have a little more information about it so they can use it correctly and safely to enhance their Keto results.

How to Safely Use the PSMF Diet Principles for Keto

I had heard of the PSMF diet from many sources in the keto space. Very few people ever mention that it’s a medical diet or give any caution about it. What I kept hearing is that it burns body fat rapidly and of course that is what we all want right?

And that is true, it does. I was stalled for 3 months, started doing some protein-sparing days and a couple weeks later I was down 9 pounds and my pants were noticeably loose.

While I was doing it, I read everything I could about it because I wanted to learn the principles behind it. Most people don’t do that and my concern is for people who see these results after a few days and decide to do it even more! Please don’t!

If you are currently doing a ketogenic diet of any kind, having stalls and weight loss plateaus is part of the process. Our bodies do need time to catch up and adjust to a new body weight low.

That said, I understand that when a weight loss stall drags on for weeks and then months, it’s frustrating! That is why I wrote this article on How to Break a Weight Loss Plateau.

frustrated with scale on keto

The Protein-Sparing Modified Fast is another tool that if used correctly (and safely!) can help you kick start your weight loss again.

So how can we use protein-sparing modified fast principles as a tool to help us get through a plateau or even get us to our goal weight?

  • Use a PSMF macro calculator to get an estimate of how many grams protein per day to eat. The calculator will also tell you calories, grams of fat and carbs as well. I used the PSMF calculator from Maria Emmerich’s site here to estimate mine.
  • Follow these macros for a MAXIMUM of 3 days per week. Preferably alternating days rather than consecutive days. Do not be tempted to think that if 3 days a week helps your weight loss along then more will be better. No, more will not be better and you will just be doing a crash diet, not making a permanent lifestyle change.
  • Keep in mind that this is a temporary diet. Once you are past your weight loss stall and things are moving again, reduce the frequency of PSMF days.

collage of foods for PSMF diet

What Am I Eating on a Protein Sparing Modified Fast Day?

The best way for me to explain it to you is by sharing my own macros for a PSMF day and then share what I typically eat. I used the macro calculator and came up with these recommended macros. (Be sure to run your own because we are all different!)

My Macros: 900 Calories, Protein: at least 140 grams, Fat: Max 30 grams, Total Carbs: Max 20 grams

The most challenging part for me was to get my protein intake up to 140 grams of protein while keeping my fat intake at 30 grams or less. I sure wasn’t able to do this with my favorite foods of rib eye steak and air fried pork belly bites!

In order to get this much protein I had to change my protein sources on those PSMF days. I chose to do 3 PSMF days per week on Monday, Wednesday and Friday. This left me 4 days a week to eat my normal amounts and do a refeeding of fat!

Lean Meat Protein Sources for PSMF Days:

  • Skinless white meat chicken breast or turkey
  • Extra lean ground chicken and turkey
  • Extra lean ground beef
  • Egg Whites
  • Fat free Greek yogurt
  • Lean cuts of beef such as eye of round, top and bottom round, top sirloin
  • Shrimp, scallops and crab
  • White flesh fish like cod and halibut
  • Pork tenderloin or loin chops
  • canned tuna (in water)

I also found that I really needed to eat 3-4 times a day, not only to make it easier to get enough protein but also I was getting hungry sooner from the lower fat intake! On my regular keto days (on which I am 99% carnivore)  I had fallen into a natural routine of intermittent fasting where I ate a meal of meat and eggs at around 10am and then a steak at 5pm and that was it. Not hungry!

But this was not the case on PSMF days. Here is a sample PSMF day (recipe links at bottom of article):

  • Breakfast: 2 Turkey Feta Burgers or 1 turkey feta burger and 1 PSMF Cinnamon Bun
  • Lunch: Chicken tenders or Shrimp with a fat free yogurt based dip
  • Dinner: Lean beef or fish or ground turkey scrambled with egg whites
  • Snack: PSMF cake or deli turkey slices

I had not counted my macros in a long time, so I also had to keep careful track on those 3 days a week to ensure that my protein grams were hitting the goal! It was challenging and I never once hit the target but still the weight just fell off. And I always had my favorite foods to look forward to the next day so it was very doable for me.

Meal prep was also key for me. During the first month where I did 3 PSMF days per week I did a meal prep of lean meats that I could just grab and go during the upcoming week.

You can watch one of my meal prep sessions here.

Proteins in storage bowls for PSMF Diet

I also tried to make it fun by cooking up PSMF Diet recipes that I have shared on Youtube! If you think that PSMF days are nothing but egg white omelets and plain chicken breast, think again!  Here are a few:

At this point in my rather lengthy dieting career (yup I’m calling it a career now!) I have lost a total of 130 pounds. That is a significant weight loss and I’m grateful for every pound of it! But each pound is getting harder and I am still 40 pounds overweight.

So I am safely and carefully using the PSMF principles as a tool to help me get closer to where I want to be. By only doing the PSMF days up to 3 times per week I feel that I am doing this in a good way and avoiding any possible nutritional deficiencies or side effects.

I will be coming back to this post to update how I did in my second month and beyond.

obese patient getting blood pressure checked

Final Cautions Before Doing PSMF

  • Do not follow the PSMF diet 7 days a week.  Three days a week max is safe to do,  the other 4 days will act like a refeeding phase to keep you not only satiated but sane!
  • Watch for side effects like headaches and nausea.  You may need electrolytes and minerals.  Try my DIY Electrolyte drink here.
  • Self check for signs of former addictive behavior coming back.  I’ve seen it in facebook groups and myself! Watch yourself to not become overly obsessive with scale numbers and macros.  If you are freaking out because you didn’t eat all your protein grams and went over on the fat grams, take a deep breath and have some bacon.  And that is no joke!  My first week (before I researched all this) I did a rotation of 2 days on PSMF and 1 day off and that was a mistake.  I felt snakey and insane.  Getting enough fat is very calming to me apparently! That week made me appreciate a simple steak.
  • DO NOT do PSMF without checking with your doctor if you have any medical conditions you are being treated for (kidney disease, cancer, high blood pressure, etc).  This is not the time to tax your body. Stay clean keto or carnivore for now.  Same if you are pregnant or nursing, your baby needs the nutrients!
  • Follow people who know what they are talking about when it comes to PSMF and don’t treat it like the latest greatest crash diet to solve all your problems.  People who stay calm and treat this with respect, not hype. See my resources below.

Further PSMF Resources

The Keto Naturopath (this link is to a podcast about PSMF)

The Keto Naturopath Youtube Channel (they have recipes and good science based info)

Maria Emmerich (video What is a Protein Sparing Modified Fast?)

My PSMF Playlist on Youtube

Save this PSMF Information to Pinterest!

Lean Proteins on white background

4 thoughts on “What is the PSMF Diet? A Practical Guide to the Protein Sparing Modified Fast”

  1. So happy to have found this article and your YouTube channel! I’m you at the start of the journey – need to lose 170lbs and I’m 63 so watching someone in their 30’s doesn’t help. Don’t need to try PSMF yet, but when I stall I know where to come for help. Thank you!

    1. We are the same age! I have so far lost 130 ish pounds with a good 40 more to go, so we will have both lost the same at the end of this journey too! Everyone has to start somewhere, congrats for starting!

    1. I don’t do it personally but that doesn’t mean that you don’t need to! I’m not a doctor or anything like that so can’t say. My own doctor has told me to supplement Vitamin D and I bought some but keep forgetting to take it!

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top