The ultimate PSMF calculator

If you’re looking to lean out in a hurry, you may be interested in the preferred weight loss strategy of bears and bodybuilders alike… the PSMF.

If you want to look lean and fit on the beach and have dreams of having abs in time for summer, you’re not alone.

The Protein Sparing Modified Fast (or PSMF) is widely recognised as being the most effective way of losing body fat while retaining as much muscle as possible.

The PSMF diet provides adequate protein to prevent loss of your precious lean mass (which is critical for your metabolic health, not just looking good naked).  

This article will tell you why it works and how to start your PSMF fat loss diet with a free PSMF calculator.

How much protein should you eat on a PSMF?

Our data analysis of half a million days of My FitnessPal data and sixty thousand days of data from Optimisers shows that we eat less when we consume a higher percentage of our energy from protein.

But, it’s not just a matter of eating more protein. Protein typically comes packaged with fat, so you need to prioritise leaner sources of protein to reduce your calories on a PSMF diet.

Dialling back the of fat in your diet tends to lead to greater satiety.

Reducing your intake of non-fibre carbohydrates also improves satiety.

While a little harder to do, your body can create all the glucose it needs from the protein in your diet. You can think of it as resistance training for your metabolism.

Dialling your intake of BOTH fat and carbs leads to greater satiety, a lower spontaneous energy intake, and then fat loss without loss of lean muscle.

How much protein do you need on a PSMF?

If you’re less active, then you might be able to get away with 1.4 g/kg lean body mass (LBM). However, if you are doing resistance training you should aim for 1.8g/kg LBM or more.

There’s no harm in targetting more protein. Lyle McDonald’s Ultimate Fat Loss Handbook recommends up to a MASSIVE 4.4 g/kg LBM protein for bodybuilders.

However, as you increase the amount of protein you will get to a point where you are not able to achieve a significant energy deficit and your range of available foods and meals will become more limited.

Easing into a PSMF diet

There’s no perfect macronutrient ratio for a PSMF. The most sustainable approach is to review your current diet and progressively dial back the refined carbohydrates and fats until you are getting the results you want.

In our Nutritional Optimisation Masterclass, we guide people to progressively dial in their macros each week to ensure they continue to achieve their target rate of fat loss.

Beyond just weight loss, we find tracking body fat is valuable to ensure you are losing fat and not muscle.

Even while losing weight, we find most people can gain a significant amount of lean mass by merely increasing the percentage of protein in their diet.

The PSMF calculator

To get started you can use this simple calculator.

  • enter your current weight
  • enter your current body fat
  • select weight loss as your goal
  • select your target rate of weight loss
  • use the slider to select your net carb intake
  • use the protein slider to dial-up your protein target

The outputs on the right will show you your target calorie, protein, fat and carb intake that you can enter into MyFitnessPal or Cronometer.

The mix of fat and carbs don’t matter too much so long as you are hitting your minimum protein target without going over your calorie limit.

Can you eat too much protein on a PSMF?

The reason that everyone is not using a PSMF is that it’s not easy to do. It’s hard to overeat protein due to the strong satiety response. Your body craves easily accessible energy from refined fat and carbs.

For best results, we recommend working up to a stretch target of 40% protein or more. As you can see in the chart below from our analysis of data from Optimisers, not many people can sustain a protein intake of greater than 40% for long.

As you consume less energy from carbs and fat your body will be forced to use up the excess glucose in your blood and then your body fat.

If you are consuming more than 40% protein and not hungry, you don’t really need to eat more of anything (including protein).

What about “rabbit starvation”?

“Rabbit starvation” happens to very lean people if they only have lean protein foods with minimum fat.  They can’t get enough energy to sustain high levels of body fat. However, for most of us who have plenty of body fat to burn, this is not going to be an issue!  

Don’t forget your micros!

But if you’re eager to try a Protein Sparing Modified Fast style diet, it is critical to ensure that you have adequate micronutrients to prevent cravings and deficiencies that can derail your long term dieting efforts.  

An aggressive energy deficit combined with poor nutrient density can be dangerous. Ensuring you are getting the essential micronutrients becomes even more critical when you are consuming fewer calories.  

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In addition to craving protein, we also have a strong appetite for micronutrients. We tend to eat fewer calories when our diet is comprised of foods and meals that contain more of these micronutrients.

You might do OK with substandard nutrition for a while, but you will do better if you are getting plenty of all of the essential nutrients.  

Ideally, you should get these nutrients from whole foods which are more likely to contain all the non-essential but also beneficial vitamins and minerals.

To help you understand what nutrients you need to focus on (and which foods and meals contain them) we have created a simple free 7 Day Food Discovery Challenge.

PSMF recipes

Finally, for people who want to jump in the deep end with a hardcore PSMF, we have created our high protein:energy recipe book.

Our Protiein:Energy Recipe Book is packed with recipes that have a super high protein percentage while still containing all the micronutrients to prevent deficiencies and cravings on your PSMF.

Further reading

The Secrets of the Nutrient Dense Protein Sparking