Who should do the PSMF diet and who shouldn't?

The protein-sparing modified fast (PSMF) diet is a way of rapidly losing large amounts of weight. It's like a battle mode for those who need/want to lose a massive chunk of fat for a certain event in the near future, like a wedding.

Essentially, it is the most science based and useful crash diet out there. While being on this diet, you're able to lose 1.5-3kg/4-7lbs of body fat and 4.5-9kg/10-20lbs of body weight in about 2 weeks. This is due to a very restricted caloric intake of around 1000 kcal per day.

It is usually used to help people lose a tremendous amount of weight and then transition into a more sustainable way of dieting.

PSMF diet is very useful when it comes to:

  • preventing muscle loss
  • appetite suppression
  • complete reliance on body fat and ketones to fuel the body

Who should do it


Initially, the PSMF diet was created to help adults with a body mass index of 30 or higher. Meaning people who are classified as highly obese.

Nowadays, this diet is also used to treat people who suffer from type 2 diabetes, hypertension, sleep apnea, osteoarthritis or fatty liver disease (hepatic steatosis).

Anyone who is sedentary and wants to lose weight in a pretty short amount of time, while preserving as much muscle mass as possible, can try a PSMF diet. All you need is extreme willpower and proper background knowledge.

Furthermore, you should be relatively healthy to do the PSMF diet. Of course, it is always best to check with your GP before starting the diet - but realistically, not everyone is going to do that. If you can't manage (or don't want) to see a doctor, you should be free of any obvious signs that something is significantly wrong with your body.

Potential side effects

Being on such a crash diet is very challenging - physically and mentally. It is a very intense diet, which might lead to behavioural changes. You might be more bad-tempered and exhausted.

Every time you remove a full segment of food from your diet, your body will react in a dramatic way. This can include:

  • headache
  • fatigue
  • blood pressure drops
  • constipation
  • menstrual changes
  • hair thinning
  • muscle cramps

Keep in mind, that these side effects aren't permanent. Either your body will adjust, or you can adjust your supplementation or fluid intake. If nothing helps, the side effects will subside when you're switching into a healthier diet program.

If you suffer from stronger side effects, make sure to consult a doctor.

Who shouldn't do it


For anybody with an existing medical condition, it is highly recommended to seek advice from a GP before starting with the PSMF diet! Furthermore, the PSMS diet is not well suited for people who are highly active or those who are following a plant-based diet.

During a PSMF diet it is recommended to limit cardiovascular activities to 20 or 30 minutes per day at a normal pace (LISS), which should be the maximum. If you want to lift weights I would advise you to consider another diet plan.

Again, the PSMF is extremely stressful for the body. Meaning, if your system can't handle the strain you might end up thinner but at the cost of screwing your body up even worse.

Furthermore, anyone without an iron will should consider a more moderate approach.

What to do instead

Are you a person, who:

Then the PSMF diet might not be the best diet for you. You should rather consider a high carb/low fat or slow carb/medium fat diet.

In general, a more sustainable way of dieting should always be considered first.

Mind the possible yo-yo effect

Restricting yourself to very few calories not only affects your body weight but also your metabolism, hormones, and health.

Being in a caloric deficit, hormonal adaption occurs, which might cause your body to burn less energy while at rest. Those hormones are leptin, ghrelin, thyroid hormones, and testosterone. And yes, all of them are affected by a weight loss diet.

One of the worst things you can do after losing weight is to dramatically increase your caloric intake back to normal. Do this and you will gain even more back than you've lost.

The solution to this problem is reverse dieting. Contrary to a weight loss diet, the reversed diet is a caloric increase. Essentially, it's adding calories slowly and controlled back into your current diet, while gaining minimal weight.

Each week (every 5 to 7 days) you increase your daily caloric intake until you reach the number of calories you're burning every day, meaning maintenance levels.

Bottom line

If you're really interested in the PSMF diet a short trial of a week or two might be beneficial to see how your body responds. Ensure your safety by consult your GP first.

To create your own PSMF diet plan, simply follow my ultimate guide.

Have you ever tried the PSMF diet? What was your experience? Let me know in the comment section below.

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