Is PSMF safe? Who should not do it, warning signs, and when to stop
A PSMF keeps you under 800 calories a day for weeks or months. That is a big change for your heart, kidneys, blood sugar and electrolytes, so clinics that use it screen people first and check blood work during the diet. Everything on this page comes from the Cleveland Clinic protocol described by Chang and Kashyap in 2014, unless it says otherwise.
Who should not do it
The review lists these as reasons not to start a PSMF:
- BMI under 27
- recent heart attack, angina, a significant heart rhythm problem, or decompensated heart failure
- recent stroke or poor blood flow to the brain
- end-stage kidney disease or liver failure
- cancer
- major psychiatric illness
- pregnancy or breastfeeding
- wasting disorders
- age under 16 or over 65
A history of gallstones or gout makes the diet riskier, and a doctor should look at that before you start. People with type 1 diabetes are usually advised against it because of the risk of diabetic ketoacidosis and the difficulty of adjusting insulin.
If you have ever had an eating disorder, tell your doctor even if it isn’t active now. A diet this strict, with daily weighing and tracking, can bring old patterns back.
Medications
Blood glucose can fall within days of starting, before much weight comes off, and blood pressure often drops too. If you take insulin, a sulfonylurea or blood pressure medicine, your doses may need to change on day one. Don’t start until your doctor has a plan for this. Low blood sugar on these drugs can be dangerous.
Side effects to expect
The review lists headache, fatigue, dizziness when you stand up, muscle cramps, feeling cold, constipation, diarrhea, bad breath, menstrual changes and hair thinning. Most of these ease with time or with changes to fluids, salt and supplements. The Cleveland Clinic protocol calls for at least 64 oz of fluid a day, a multivitamin, and set amounts of potassium, calcium, magnesium and sodium. Your doctor should set the potassium and magnesium doses, because too much potassium is dangerous for some people, especially those with kidney disease or on certain blood pressure drugs.
When to stop and get help
Stop the diet and contact your doctor if you have any of these:
- a racing, pounding or irregular heartbeat
- fainting, or dizziness that doesn’t pass when you sit or lie down
- chest pain or shortness of breath (call emergency services)
- severe pain in the upper right or middle of your belly, especially after eating, which can mean gallstones
- a hot, swollen, very painful joint, often the big toe, which can mean gout
- confusion, shaking, sweating or extreme weakness if you take diabetes medicine, which can mean low blood sugar
- vomiting or diarrhea that stops you keeping fluids down
- muscle cramps or weakness that keep getting worse
Chest pain and fainting are emergencies. Don’t wait for an appointment.
The checks clinics run
At Cleveland Clinic, patients get an ECG before they begin, to rule out rhythm problems. They get blood work at the start, every 2 weeks for the first month, and monthly after that. They meet a dietitian and see a physician or nurse practitioner every 6 to 8 weeks. You can ask your own doctor for a similar schedule.
Stopping safely
Don’t jump straight from a PSMF back to normal eating. The protocol uses a 6 to 8 week refeeding phase that adds carbohydrate and fat back slowly. The start here guide has the numbers.