On the basis of studies of fair or poor quality, several having low levels of evidence, AETMIS concludes the following:
The PSMF diet is in no way indicated for people who are not overweight.
In cases where people are required to lose weight, the leading recommendation by nutrition experts is to prescribe a personalized, balanced moderately low-calorie diet with an energy deficit ranging from 500 to 1000 kcal/d.
Experts are divided on the place of the PSMF diet as a therapeutic option for obesity. Some believe that the PSMF diet has no place in the current range of dietary interventions. Others, in official position statements, do not exclude its use and consider that it may be used for limited indications, especially in the management of people with obesity (BMI ≥ 30 kg/m2) or people with a BMI between 27 and 30 kg/m2 who have failed to lose weight on previous well-managed, conventional diets, who face overweight-related medical complications causing a serious health risk and who therefore need to begin losing weight quickly.
Examination of the scientific evidence provided in studies on PSMF diets in clinical settings reveals the following:
Compliance with this diet is difficult and attrition rates are high.
Short-term weight loss is rapid and significant and is accompanied by also short-term changes in clinical and biological parameters suggesting improvements in some associated risks.
Its long-term efficacy for weight loss remains less certain, given the conflicting outcomes of the two meta-analyses evaluating this aspect.
In addition, no evidence was found to conclude on the benefit of repeated courses of PSMF.
The adverse effects and complications observed require medical supervision during the fasting stage.
The potential costs and savings generated by PSMF diets, of which little is currently known, should be subjected to in-depth study.
Given the lack of long-term efficacy of this diet for real weight loss and its reported dangers, compared with conventional weight-reduction diets, and given the need for medical monitoring, although little documented, combined with a multidisciplinary intervention involving other health professionals, the principle of medical precaution (primum non nocere) is warranted, while that of refraining from the use of this diet must be considered.
When used, the PSMF diet should be an integral part of the patient’s general support program conducted by a multidisciplinary team and including physical activity, support for changing eating behaviour, potential psychological follow-up, etc., as in the case of a balanced moderately low-calorie diet.
The extent and nature of health professional involvement in this process have not been fully elucidated. The existence of possible adverse effects from PSMF diets demonstrates the importance, in terms of safety, of ensuring that this diet is prescribed by a qualified physician and monitored by health professionals. Given all of these elements, it would be important to draw up a profile of the use of this type of diet in Québec with its achieved outcomes.
Reflection on the place of this nutrition therapy could be part of a general reflection on the management of obesity, which would include all concerned parties. Lastly, the place of the different professional practitioners in conducting diets geared toward intentional weight loss, including PSMF, will remain difficult to recognize so long as there is reluctance to acknowledge that obesity is a complex chronic disorder requiring consideration of its biological, social and psychological dimensions.