A protein-sparing modified fast or PSMF diet is a type of a

very-low-calorie diet A very-low-calorie diet (VLCD), also known as semistarvation diet and crash diet, is a type of diet with very or extremely low daily food energy consumption. VLCDs are defined as a diet of per day or less. Modern medically supervised VLCDs use me ...

(<800 kcal per day) with a high proportion of protein calories and simultaneous restriction of carbohydrate and fat. It includes a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

component,

fluids In physics, a fluid is a liquid, gas, or other material that may continuously move and deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot res ...

, and vitamin and mineral supplementation. PSMF diets can last for up to 6 months, followed by a gradual increase in calories over 6–8 weeks.

Description

A PSMF attempts to spare the dieter the health risks of a complete fast by introducing the minimum amount of protein necessary to prevent muscle-wasting effects, while still eliminating fats and carbohydrates. Typically, depending on activity level, 0.8–1.2 g of protein per pound of lean body mass (not total body weight) is consumed. Protein beyond this minimum amount is also eliminated, as the body would use it for energy in a process called

gluconeogenesis Gluconeogenesis (GNG) is a metabolic pathway that results in the biosynthesis of glucose from certain non-carbohydrate carbon substrates. It is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In verte ...

. Further lean body mass (muscle, organs, etc.) are spared through resistance training and limiting aerobic activity.

History

The Last Chance Diet

The concept of "protein-sparing modified fast" (PSMF) was described by George Blackburn in the early 1970s as an intensive weight-loss diet designed to mitigate the harms associated with protein-calorie malnutrition and nitrogen losses induced by either acute illness or hypocaloric diets in patients with obesity, in order to adapt the patient's metabolism sufficiently to use endogenous fat stores as well as to preserve the protein contained in the body cell mass. The "liquid protein" PSMF diet described in the book ''The Last Chance Diet'' in 1976, motivates that the liquid protein diets of varying composition became widely popular. Three years later, in 1979, Isner published a report of 17 deaths associated with liquid protein VLCD, due to heart-related causes. These serious effects caused a substantial concern about the safety of clinical use of PSMF and VLCD. As a result, a review was published that highlighted the differences between these liquid protein diets, arguing that the fatal diets typically used hydrolyzed collagen (gelatin) supplemented with the amino acid

tryptophan Tryptophan (symbol Trp or W) is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromat ...

for protein but that this omitted the other 8

essential amino acids An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms ...

; it further emphasized the importance of close medical monitoring during the fast and refeeding periods.

Modern PSMF diets

Instead of hydrolyzed collagen, modern medically supervised PSMF diets include foods of higher

biological value Biological value (BV) is a measure of the proportion of absorbed protein from a food which becomes incorporated into the proteins of the organism's body. It captures how readily the digested protein can be used in protein synthesis in the cells of ...

, such as meat, fish, eggs, cheese, and/or tofu. PSMF is used as a treatment for highly motivated patients to achieve rapid weight loss and usually is administered for 6 – 16 weeks. Before an individual starts a PSMF diet, their doctor should order an electrocardiogram, to check for signs of heart disease and also will prescribe specific vitamins minerals and electrolytes to be taken daily as long as the diet persists.

References

{{Fad diets Fasting Proteins as nutrients Fad diets fr:Régime protal nl:Dukan-dieet pl:Dieta proteinowa

Description

History

The Last Chance Diet

Modern PSMF diets

See also

References