“Protein-Sparing Modified Fasting” is such a valuable tool when your goal is weight loss, and you feel that you may have hit a plateau. This type of fasting has been called many names and has been used in many ways. However, the name “Protein-Sparing Modified Fast” was coined by Maria Emmerich. Long before the Keto Diet became a thing, Mario called this practice a Pure Protein day (around 2010). The idea behind a Protein-Sparing Modified Fast is to reduce the carbs and fat as much as possible while still having your protein goals or even a bit more protein than usual.
However, it is most effective when you have become fully keto-adapted. For you to really tap into this powerful weight-loss tactic, you want your body to be super-efficient at burning fat for fuel. This is not really a tactic you want to deploy in your early stages of starting the Keto Diet when your body is still transitioning from using carbs (glucose) for energy to using fat (read more on Keto-adaptation on this blog).
Once you become fully keto-adapted, you will note that eating less food becomes much easier because the body has now learned to use stored fat for energy and don’t need those continual snacking to entertain the constant cravings (read more on why the Keto Diet eliminates cravings here).
WHY THE PROTEIN SPARING MODIFIED FAST
The whole idea behind the Protein-Sparing Modified Fast is to reduce your carbs and fat as much as possible while slightly increasing your protein intake. So that you force your body to tap into your own fat stores even more. I usually start my clients at about 1.8 grams of protein per kg of lean body mass. On the Protein-Sparing Modified Fast, I will take their protein intake up to about 2.2g per kilogram of lean body mass. Even though we want to get our fat intake as low as possible, we still want to get some fat in during the fast to ensure that we keep our hormones happy and that all the fat-soluble vitamins get absorbed. I usually aim for between 40g and 60g of fat for the day.
The additional protein makes your body use even more stored fat for fuel, which helps break plateaus and accelerate weight loss. It also gives you the added benefit of the high thermic effect caused by digesting food with protein. This thermic effect helps burn fat as well, and can effectively count for up to 25% of the calories you take in.
Like intermittent fasting, we suggest that you do it every once in a while; maybe a day or two a week to break a plateau or to increase fat loss.
Let me give you an example of one of my clients (Let’s call her Suzy… which is not her real name):
- Suzy weighs 70kg with 35% body fat and is not active at all.
- She wants to do Keto to improve her health and lose some weight
- Suzy has a BMR (Basal Metabolic Rate) of about 1395 calories.
- When she starts my Keto Coaching Program, I will start her on a 15% calorie deficit with about 70% of her calories coming from fat and 1,8g of protein per kilogram lean bodyweight. On an average day, she will eat about 80 grams of protein, 100 grams of fat, while keeping her carbs below 20g. This tallies up to about 1300 calories per day.
Once I am confident that Suzy is fully keto-adapted, which happens after about 4 – 5 weeks on my Keto Coaching Program, I introduce the Protein-Sparing Modified Fast as well as intermittent fasting to accelerate fat loss.
HOW DO I DO THE PSMF
Typically I will do one protein-sparing modified fast and one 16/8 intermittent fast per week.
Suzy’s Protein-Sparing Modified Fast will now look like this for the day:
- I will increase our protein to 2,2 grams of protein per kg lean body mass, which totals to about 100 g of protein.
- I will decrease total fat intake to about 50 grams of fat for the day.
- She will continue keeping her carbohydrates under 20 grams.
- This leaves her with about 900 calories for the day.
She will get enough protein to preserve important lean body mass, but she will have to use a lot of still fat to fuel her body. I have seen this tactic to be such an effective way to accelerate weight loss and breaking through a plateau.