Protein-Sparing Modified Fasting

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Protein-sparing modified fasting (PSMF) can be dangerous, even fatal, if you perform it incorrectly. If your goal is to achieve a normal weight, you don’t need this technique. I recommend that you use one of the other strategies instead.

If you choose to attempt it, read the “Safety” section below several times. I do not personally endorse or recommend that you attempt PSMF. You’ve been warned.

Now that the warning is out of the way, this technique does have great merits for weight loss, but it’s absolutely overkill in 95% of all situations.

It’s most useful if you’re someone who’s at a low body fat (-14% for men, -25% for women) trying to get ripped or vascular.

How It Works

Protein-sparing modified fasting allows you to experience a majority of the rapid fat loss benefits of water fasting while continuing to eat regularly. But there’s a huge catch:

You can only eat protein (with extremely trivial amounts of fat and carbs).

PSMF relies on the fact that only fat and carbohydrate calories are efficiently used as energy for the body. Any energy gained from protein is trivial. The goal is to eat almost all protein and as little fat and carbs as possible (<10-20g of each per day). This way, your body will be forced to use stored energy all of the time.

There are really only two benefits to choosing PSMF over water-fasting:

  1. You can eat.
  2. You can continue to exercise (with intensity) with less risk of muscle loss.

Eat as much as you want, give you eat it within a specified time of day. At minimum, eat 1g of protein per pound of your lean body weight. If you don’t know your lean body weight and can’t come up with a fair estimate, you shouldn’t be running this diet.

PSMF is a crash diet. It is neither intended to be long-term nor sustainable.

Allowed Foods

Here’s a list of most of the foods you can eat on PSMF:

  • Skinless chicken breast (trim off the extra fatty bits)
  • Skinless turkey breast
  • Super lean ground chicken/turkey/beef
  • Egg whites
  • No-carb, no-fat whey protein powder
  • Fat-free cottage cheese (in moderation)
  • Fat-free cheese (in moderation)
  • Calorie-free condiments (like mustard, hot sauce)
  • Low-calorie, low-carb vegetables (really just to fill you up)
  • Water, black coffee, tea, diet soda

Doesn’t that sound like fun? Depending on your tastes, it can get expensive too. Buying protein powder and chicken breasts in bulk will probably save you the most money.


PSMF is stressful on the body. If you have any pre-existing medical conditions or are experiencing any type of physical or mental stress, do not attempt this diet.

Eat one or two meals per day within a 4-8 hour period. This is important because eating many small meals throughout the day causes consistent insulin release which will prevent your body from using its stored energy. You can starve yourself if you mess this up.

Ensure that the food you’re eating is actually low carb and fat. If you eat too much energy for PSMF, but not enough for standard expenditures, you may damage your metabolism.

Advice for exercising safely on PSMF is outside the scope of the guide. Don’t try it without seeking more information.


Admittedly, I didn’t discover PSMF until my body fat percentage was already low, but I can tell you from personal experience that this is a mentally challenging diet. The lack of options and no satiating fat makes for a tough time.

As with the other diets, I’d expect that the higher your initial body fat percentage is, the less mentally stressful the diet will be for you.

If you’re experiencing significant mental stress in your life, it will probably increase the difficulty of sticking to the diet.

That’s it for my recommended weight loss strategies. If you don’t like any of them, you can come up with your own as long as you follow the blueprint for fat loss. (Just remember that if you choose not to follow the it, you’ll be fighting an uphill battle against your biology. Anything worth attaining requires some type of sacrifice.)

From this point, you can read about what would happen if you ate all carbs or the read about the role exercise can play into fat loss.

You can also move onto the first guide.