Dietary Approaches

Food rules in religious fasting traditions

A review of religious fasting describes three Christian and Muslim examples with distinct rules. Ramadan is a fast of 28 to 30 days in which food and drink are prohibited during daylight hours. Greek Orthodox Christians fast for a total of 180 to 200 days a year, mainly in the Nativity Fast, Lent and the Assumption period, and the review describes these periods as variants of vegetarianism. The Daniel Fast is a Biblical-based fast that excludes animal products and several other food groups. A second review by the same lead author notes that many religions incorporate one or more forms of food restriction.

The reviews reached these descriptions from studies of Islamic and Greek Orthodox communities and of the Daniel Fast. The sources reviewed here do not cover Hindu, Buddhist, Jain or Jewish food practices, so this page makes no statement about them.

Named patterns from the twentieth century onward

Dated origin accounts are sparse in the sources reviewed. The Cochrane review of Mediterranean-style diets notes that the Seven Countries study in the 1960s showed lower coronary heart disease mortality in Mediterranean populations, probably linked to dietary patterns, and that later trials tested that idea. A review of the autoimmune protocol cites a 2013 book, The Paleo Approach, as its primary source and calls the protocol a stricter extension of the Paleolithic diet. A study of macrobiotic menus cites Kushi Institute guidance but does not name a founder.

The DASH name stands for Dietary Approaches to Stop Hypertension, according to the NHLBI page, which gives no development history. For most other patterns in this family the sources reviewed give no dated founding account, and this page does not supply one.

Dietary pattern versus single nutrient

This page uses dietary approach for a named pattern of what, when or how people eat, as opposed to a single nutrient or a supplement. The WHO fact sheet frames a healthy diet through adequacy, balance, moderation and diversity, and states that exact food choices vary with age, activity, culture and local food availability. The American diabetes nutrition consensus report likewise states that no single eating pattern has emerged as clearly superior for all diabetes outcomes.

Unsettled and overlapping names

Several labels in this family have no agreed definition. A scoping review found no formal definition of flexitarian eating and many competing terms, including semi-vegetarian, and found that no national food-based guideline reviewed used the word flexitarian. The diabetes report states that intermittent fasting is not an eating pattern by definition, since it concerns timing. Detox diets form a marketing category rather than a defined pattern: the critical review of detox diets examined what such diets involve rather than a single protocol.

Professional titles are also unsettled. The British Dietetic Association states that dietitian is the only nutrition title tied to statutory registration in the UK, that nutritionist titles may be used by anyone, and that nutritional therapists may join a voluntary register.

Composition-based patterns

Composition-based patterns define which foods feature. The Cochrane review defines a Mediterranean-style diet by a high ratio of monounsaturated to saturated fat, with olive oil or tree nuts, and a high intake of plant foods such as fruits, vegetables and legumes. The NHLBI describes DASH as a flexible, balanced eating plan emphasizing vegetables, fruits, whole grains, low-fat dairy, fish, poultry, beans, nuts and vegetable oils. The NHS describes vegetarian eating as excluding meat and fish, and vegan eating as excluding all animal-derived foods, including dairy and eggs.

Other composition-based patterns sit at the edges. Self-identified carnivore dieters in one survey ate animal foods and excluded most or all plant foods. A German study defined strict raw food eating by avoiding food warmed above a set temperature, and found a narrow food range. The alkaline diet emphasizes fruits and vegetables and limits foods its proponents class as acid-forming, resting on the acid-ash idea. A modeled macrobiotic menu was predominantly vegetarian, seasonal and mostly whole-foods.

Fasting and timing-based patterns

Timing-based patterns change when food is eaten rather than which foods. The Cochrane review describes intermittent fasting as eating patterns with little or no energy intake for extended periods alternated with normal intake, including time-restricted feeding, alternate-day fasting and periodic fasting. Calorie restriction is described in a review as reduced intake, typically while maintaining adequate nutrients. Water-only fasting and juice-only diets go further and restrict everything but water or juice, and the case reports reviewed here describe complications of both.

Elimination and restriction programs

Elimination programs remove groups of foods, sometimes with a staged return. The British Dietetic Association guideline places low-FODMAP advice as second-line dietary advice for irritable bowel syndrome, provided by a dietitian. The autoimmune protocol is described in a review as an elimination phase, a reintroduction phase and a maintenance phase. A gluten-free diet is the main treatment after a diagnosis of coeliac disease. Ayurvedic dietary advice in one trial was individualized around digestive strength, with warm food and regular meal times.

Uses with a clinical basis

Several patterns are used for named conditions. Ketogenic diets are used for drug-resistant epilepsy, and the Cochrane review calls them a valid option for people with drug-resistant epilepsy who are unsuitable for surgery. A gluten-free diet is the main treatment for coeliac disease, and a low-FODMAP diet is second-line advice for irritable bowel syndrome. Mediterranean-style diets are tested for cardiovascular prevention, and DASH is described as a heart-healthy plan.

Wellness and other claims

Other uses are claimed by advocates rather than established in guidelines. The detox diet review states that such diets claim to facilitate toxin elimination and weight loss. The alkaline diet rests on the claim that acid-forming foods draw calcium from bone. Carnivore dieters in a survey were motivated mainly by health reasons. Macrobiotic diets are popular partly because of reports attributing recovery from poor-prognosis cancers to them, which the modeling study notes but does not test.

Religious fasting rules serve spiritual purposes, and the reviews studied health markers as a secondary question. The sources reviewed do not catalog ethical or cultural motivations in detail.

Patterns tested in trials and guidelines

The Cochrane review of Mediterranean-style diets included 30 randomized trials with 12,461 participants. It reported moderate-quality evidence of lower blood pressure in primary prevention and of fewer strokes in the PREDIMED trial, a trial that was retracted and re-analyzed. It concluded that uncertainty remains for clinical outcomes and that evidence for secondary prevention is scarce.

The Cochrane review of ketogenic diets for drug-resistant epilepsy included 13 studies with 932 participants and rated all evidence low to very low certainty. Results favored ketogenic diets in children, but the review was not confident in the estimates and called the evidence in adults uncertain. The British Dietetic Association guideline for irritable bowel syndrome appraised 86 studies and supports low-FODMAP advice as second-line, dietitian-delivered care.

In diabetes care, the consensus report finds no ideal mix of nutrients and no single pattern superior for all outcomes. It reports that low-carbohydrate benefits for A1C were seen at 3 and 6 months but not at 12 and 24 months, and that evidence on intermittent fasting comes from small, short studies.

Patterns with little or no trial evidence

For other patterns the sources reviewed describe thin evidence. The carnivore diet survey of 2029 self-selected adults relied on self-report and noted markedly elevated LDL cholesterol in a subset. The alkaline diet review found no substantial evidence for bone benefit and no literature showing cancer prevention. The detox diet review found no randomized trials of commercial detox diets in humans. The autoimmune protocol review found only a few small, mostly uncontrolled studies.

Searches of PubMed and Europe PMC for Master Cleanse and for juice fasting or juice cleanse returned no clinical trials, only one study that used Master Cleanse descriptions as test items and a few case reports. The raw food study had 16 participants, the macrobiotic study modeled menus without measuring outcomes, and the single Ayurvedic trial was open-label with a wide confidence interval and inconsistent statistics.

Fasting and results that do not transfer

The Cochrane review of intermittent fasting in adults with overweight or obesity included 22 trials with 1995 participants. Against regular dietary advice it found little to no difference in weight loss, with low-certainty evidence, and very uncertain evidence on adverse events. Follow-up was at most 12 months.

Results also do not transfer between patterns or conditions. A network meta-analysis in multiple sclerosis compared eight dietary interventions, including Mediterranean, ketogenic and Paleolithic diets, across 12 trials, and rated the credibility of every direct comparison as very low. Reviews of religious fasting report mixed findings for Ramadan and some favorable lipid findings for Greek Orthodox fasting, in communities and conditions that differ from wellness fasting.

Medically indicated therapeutic diets

A therapeutic diet is prescribed for a diagnosed condition. The NHS places a gluten-free diet after a diagnosis of coeliac disease and describes referral to a dietitian and annual review. The British Dietetic Association guideline places low-FODMAP advice as second-line advice delivered by a dietitian. Ketogenic diets for epilepsy are described in the Cochrane review as an option for drug-resistant disease, and a nephrology review advises close medical supervision when ketogenic diets are used in chronic kidney disease.

Wellness use of the same names

The same names are used outside clinical settings, and evidence from a therapeutic use does not carry across. The epilepsy review supports ketogenic diets in drug-resistant epilepsy, not weight loss or general wellness. The coeliac evidence supports gluten-free eating in coeliac disease, not in people without it. The diabetes report applies to adults with diabetes or prediabetes. Fasting-based patterns differ from composition-based patterns in what they change: timing or total intake instead of food choice, which is why trial results for one do not predict the other.

Eating disorders and dietary restriction

The NHS describes eating disorders as mental health conditions in which food is used to manage feelings, notes that people of any age can develop them and advises seeing a GP early. The diabetes consensus report states that the safety of intermittent fasting in people with disordered eating has not been studied, and the autoimmune protocol review advises that people with eating disorders avoid that protocol. In one correlational online study, people at risk of an eating disorder endorsed false diet claims, including Master Cleanse descriptions, somewhat more often; the study does not show that any diet causes an eating disorder.

Pregnancy, children, infants and low body weight

The NHS says vegetarian and vegan eating needs planning for pregnancy, breastfeeding and childhood, and that vegan diets can miss calcium, iron, vitamin B12, iodine and selenium. The WHO recommends exclusive breastfeeding for the first 6 months. A report of three infants fed homemade formula based on alkaline diet recipes described severe hypocalcemia and rickets, and the authors warned against homemade formula. In 16 strict raw food eaters, three were underweight and vitamin B12 status was lowest, so meeting energy needs was difficult.

Diabetes, kidney disease and prolonged restriction

The consensus report names the dietitian as the preferred provider of diabetes nutrition therapy; the sources reviewed here do not detail interactions between specific diets and glucose-lowering medicines, so that question belongs with a clinician. The WHO notes that excess protein can strain the kidneys, and a nephrology review lists acid-base, electrolyte, stone and protein concerns for ketogenic diets in kidney disease. A case report described Wernicke's encephalopathy and refeeding syndrome after a 40-day water-only fast, and another described acute kidney injury after a juice-only diet in an older man with diabetes. The ketogenic epilepsy trials reported mostly vomiting, constipation and diarrhea.

Guidelines, titles and care boundaries

The WHO fact sheet sets the population-level baseline against which named diets are compared. This page could not open the US Dietary Guidelines or NICE guidance, so it does not summarize them. Training is described by professional bodies: the BDA says UK dietitians are tied to the HCPC register after approved degree routes, and the US Commission on Dietetic Registration lists a graduate degree, accredited supervised practice and an examination. Nothing on this page is individual advice; a diet should not delay or replace necessary care.