Protein Sparing Modified Fast (PSMF)
The Protein Sparing Modified Fast (PSMF) is regarded by many to be the most effective way to lose body fat while preserving muscle and avoiding rebound binge eating due to nutrient deficiencies.
First developed in the 1970s, the PSMF has seen various permutations in weight loss clinics and the bodybuilding community. A PSMF generally defined as a diet with adequate protein, while simultaneously limiting energy from carbohydrates and fat.
There’s nothing really magical about a PSMF. It just means that you pay particular attention to protein in an energy deficit.
If you want to lose weight quickly and body fat fast you need a more substantial deficit, and therefore more attention needs to be paid to ensuring you are getting adequate protein.
Medical PSMF
Protein levels are set at 1.2 to 1.5 g/kg of ideal body weight per day. Note: For someone with 30% body fat wanting to get to 10% body fat this would be equivalent to 1.5 to 1.9g protein per kilogram of lean body mass or LBM.
Lyle McDonald PSMF
Rapid Fat Loss Handbook.
If you are active and/or doing resistance training a recent review paper by Stuart Phillips, lean muscle mass is best preserved when we have at least 2.6g/kg total body weight where there is an aggressive deficit (e.g. 35%). A lower protein intake of 1.5 g/kg body weight seems to be adequate with a more moderate deficit.
Summary
Attaining adequate micronutrients can help to mitigate metabolic/mitochondrial slowdown and adaption to the severe calorie deficit. If we are getting the range of micronutrients we need, the body is more likely to keep on feasting on our own fat stores without reacting like there is a famine.
A PSMF is never a zero calorie fast as it will have enough calories to get the protein you need and ideally some essential fats and adequate vitamins and minerals. People with more fat to loss will be able to maintain a more significant deficit for longer without losing muscle than lean bodybuilders.
The Protein Sparing Modified Fast (PSMF) is regarded by many to be the most effective way to lose body fat while preserving muscle and avoiding rebound binge eating due to nutrient deficiencies.
First developed in the 1970s, the PSMF has seen various permutations in weight loss clinics and the bodybuilding community. A PSMF generally defined as a diet with adequate protein, while simultaneously limiting energy from carbohydrates and fat.
There’s nothing really magical about a PSMF. It just means that you pay particular attention to protein in an energy deficit.
If you want to lose weight quickly and body fat fast you need a more substantial deficit, and therefore more attention needs to be paid to ensuring you are getting adequate protein.
Medical PSMF
Protein levels are set at 1.2 to 1.5 g/kg of ideal body weight per day. Note: For someone with 30% body fat wanting to get to 10% body fat this would be equivalent to 1.5 to 1.9g protein per kilogram of lean body mass or LBM.
- Carbohydrate intake is typically restricted to less than 20 to 50 g/day.
- Additional dietary fat beyond what comes with lean protein sources is minimised.
- Patients in the weight loss clinic setting (e.g. for morbidly obese people in the lead up to bariatric surgery) are restricted to less than 800 kcal/day.
Lyle McDonald PSMF
Rapid Fat Loss Handbook.
- Protein intake ranges from 2.2 g/kg LBM to 4.4 g/kg LBM
- Unlimited green leafy fibrous veggies
- McDonald also recommends supplementing with a multivitamin, sodium potassium, magnesium, taurine, calcium and fish oil.
If you are active and/or doing resistance training a recent review paper by Stuart Phillips, lean muscle mass is best preserved when we have at least 2.6g/kg total body weight where there is an aggressive deficit (e.g. 35%). A lower protein intake of 1.5 g/kg body weight seems to be adequate with a more moderate deficit.
Summary
Attaining adequate micronutrients can help to mitigate metabolic/mitochondrial slowdown and adaption to the severe calorie deficit. If we are getting the range of micronutrients we need, the body is more likely to keep on feasting on our own fat stores without reacting like there is a famine.
A PSMF is never a zero calorie fast as it will have enough calories to get the protein you need and ideally some essential fats and adequate vitamins and minerals. People with more fat to loss will be able to maintain a more significant deficit for longer without losing muscle than lean bodybuilders.
- The protein sparing modified fast (PSMF) provides adequate levels of protein to support lean muscle mass while restricting energy from carbohydrates and fat.
- Protein intakes vary widely depending on the goals and the level of energy restriction between.
- Providing adequate nutrients, ideally from whole foods, is critical to long-term weight loss and maintenance.
- It is crucial to prioritise nutrient-dense foods to improve your chances of long-term success.
- While the PSMF is commonly used in weight loss clinics and the bodybuilding community, the principle can also be applied in other situations to maximise fat loss while maintaining lean muscle mass.