Review articleFasting in mood disorders: neurobiology and effectiveness. A review of the literature
Introduction
Humanity, until recently, has been exposed to large fluctuations in the availability of its food, alternating periods of over-feeding and starvation. Periodic fasting with voluntary restriction of the intake of solid food is practiced around the world, mostly for cultural or religious reasons (fasting is thought to favor man's awakening to spirituality) (Buchinger, 1950, Buchinger, 1952, Heun, 1954a, Heun, 1954b, Heun, 1956, Rooth and Carlstrom, 1970). Since Hippocrates, fasting has been offered as treatment of acute and chronic diseases, following the empirical observation that infection is frequently accompanied by an anorexic response (Exton, 1997, McCarthy et al., 1985). The deliberate choice of fasting in some religions as renunciation of external rewards in an ascetic approach could be strengthened by the concomitant increase in mental alertness, sense of calm and improved mood. Mood alleviation during fasting may represent an adaptive mechanism promoting phylogenetic struggle for survival and search for food. Thus, the human body may be programmed to cope with famine, but not with over-feeding.
Very low calorie diets allow up to 800 kcal/day. Caloric restriction is defined by a decrease in daily calorie intake by 30–40% (Varady and Hellerstein, 2007). Dietary restriction below 500 kcal/day initially triggers a strong neuroendocrine activation that leads to rapid mobilization of glycogen stores (Phase I), followed after 24 h of fasting by the lipolysis of fat mass (phase II) that precedes a phase of accelerated protein catabolism (phase III). This protein catabolism is significantly reduced by the intake of 200–500 kcal/day in the form of fruits or soups: this defines fasting therapy, also called modified/therapeutic fasting, which is focused upon in this review (Varady and Hellerstein, 2007). Optimal medical fasting is defined as 2 days of 800 kcal/day diet in the form of fruit or rice or potatoes. The patient then receives a small amount of oral laxative. While fasting, it is recommended that the patient drink 2–3 liters of fluid per day (mineral water, small amounts of fruit juice, tea). Food is gradually reintroduced at the end of fasting (after 1–3 weeks) and ends with taking normal-calorie vegetarian dishes at day 4 after fasting cessation. This period of re-introduction is accompanied by a focus on feeding mindfulness.
Medical fasting is still practiced on a voluntary patient basis, and its duration is limited and predefined (Michalsen, 2010). The recommended duration of fasting in the indication “chronic pain” is 1 to 2 weeks. Standardized methods of medical fasting were developed in the United States in the early 20th century by Dewey Tanner and Hazzard but have since disappeared from this country, although this method has been increasingly successful in Europe since the 1950s. The most used method is one proposed by the German physician Otto Buchinger: it is defined by fasting for 1–3 weeks with the ingestion of mineral water and fruit juice in limited amounts, accompanied by a moderate level of physical exercise (Buchinger, 1950, Buchinger, 1952, Buchinger, 1953, Buchinger, 1959a, Buchinger, 1959b).
Medical fasting is well established and has been shown to be safe. Rare side effects include irritability, headache, fatigue, nausea and stomachache. Contra-indications (Bol’shova and Malinovs’ka, 2008, Henry and Gumbiner, 1991, Le Bourg, 2005) are eating disorders, a body-mass index below 20 or above 40, kidney or liver disease, gastric ulcer, severe comorbidities, including cancer, immunosuppressive premedication (except corticosteroids), alcoholism, psychosis, pregnancy, lactation, unexplained weight loss, and medication with diuretics (in order to avoid hyponatremia).
The reported patient adherence rate is known among chronic pain disorders. Periods of prolonged fasting (>8 days) seem to be better tolerated than periods of intermittent fasting, where the sensation of hunger is more poorly tolerated during the days of food restriction. Similarly, periods of prolonged fasting seem easier to set up than caloric restriction in daily life (Bol’shova and Malinovs’ka, 2008, Buchinger, 1959b, Busse Grawitz, 1952).
Intermittent fasting and caloric restriction increase life expectancy of all animal species in which they have been tested (Bartke et al., 2007, Barzilai and Bartke, 2009, Cox and Mattison, 2009, Everitt and Le Couteur, 2007, Gillette-Guyonnet and Vellas, 2008, Masoro, 2007, Masoro, 2009, Omodei and Fontana, 2011, Segall, 1977, Skulachev, 2011, Trepanowski et al., 2011, Willcox et al., 2007). They have also recently demonstrated in humans an efficacy in the prevention of degenerative diseases (such as Alzheimer's or Parkinson's) (Jadiya et al., 2011, Love, 2005, Mattson, 2003, McCarty, 2001, Patel et al., 2005, Srivastava and Haigis, 2011) of cardiovascular disease (Ahmadi et al., 2011, Cefalu et al., 1997, Cefalu et al., 2004, Cruzen and Colman, 2009, Gerstenblith, 2006, Mattson and Wan, 2005, Shinmura, 2011, Williams et al., 2002), diabetes (Hammer et al., 2008, Henry et al., 1985, Nagulesparan et al., 1981, Polonov et al., 1982, Skripchenko et al., 2002, Ugochukwu and Figgers, 2007, Wycherley et al., 2008) and cancer (Buschemeyer et al., 2010, Elias et al., 2007, Kritchevsky, 1993, Kritchevsky, 2001, Manjgaladze et al., 1993, Michels and Ekbom, 2004, Sell, 2003, Steinbach et al., 1994, Thompson and McTiernan, 2011) and in the treatment of rheumatoid arthritis, chronic pain syndromes and migraine (Michalsen, 2010, Michalsen et al., 2006, Michalsen et al., 2003b, Michalsen et al., 2002). All studies found that the modified fast is safe and is not associated with a feeling of hunger that may potentially lead patients to discontinue treatment (Michalsen et al., 2005).
A significant proportion of patients in psychiatry have a lack of response to drugs, sotherapeutic fasting may be a treatment of interest in addition to or in place of psychotropic medication. Moreover, therapeutic fasting has a low cost and is easier to carry out than other treatments for drug-resistant patients, such as electroconvulsive therapy, for example.
As we found no review on therapeutic fasting and its effectiveness in mood improvement, this study aims to explore the biological mechanisms activated during fasting that could have an effect on brain function with particular focus on mood (we do not discuss here the mechanisms regulating eating behavior) and to provide a review of data suggesting the efficacy of therapeutic fasting on mood.
Section snippets
Process
The Medline, Web of Science, and Psycinfo databases were searched from their inception until October 2012 according to the PRISMA criteria (Preferred Reporting Items for Systematic reviews and Meta-Analysis). English, German and French language restrictions were applied. As the words “mood” or “depression” were too restrictive, we checked all data on fasting's effects and selected relevant articles. Duplicates were eliminated. Reference lists of identified original and review papers were
Results
Nighty-two articles were included in the qualitative synthesis.
Limits and perspectives
Randomized controlled clinical trials studying the effectiveness of fasting on major depression have yet to be carried out. The heterogeneity of available studies, regarding samples, fasting process, and assessment of mood cannot form the basis for a meta-analysis, and it is not possible to date to conclude that fasting significantly improves mood, even if clinical findings are encouraging. We limited this review to published studies written in English French and German, so we may have missed
Conclusion
Therapeutic fasting has been a safe practice in the medical community for a century, and in some religions for millennia. Research on therapeutic fasting is similar in some aspects to date to research on anti-inflammatory drugs in psychiatric disorders 10 years ago. At the time, only observations on populations of patients with chronic diseases (cancer, Crohn's disease, psoriasis in this case) reported an improvement in mood in patients treated with anti-inflammatory drugs. Today many studies
Acknowledgments
Dr Jean-Benoit Cottin and Dr Isabelle Chaudieu (INSERM 1061, Montpellier, France).
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