Special Diets
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Special diets
Understand plant-based eating, carbohydrate restriction and fasting—and build a pattern that nourishes your life.
Food choices can express care for animals, cultural traditions, environmental concerns, personal preferences and health goals. A named diet can provide a useful structure, especially when it makes shopping and cooking easier to organise.
It also helps to understand what the name leaves unsaid. “Vegan” describes which foods are excluded. “Low-carbohydrate” describes a change in nutrient proportions. “Intermittent fasting” describes an eating schedule. None of these labels, by itself, tells you whether someone is getting enough nourishment or whether the approach suits their circumstances.
This guide explains the main differences, what human research can tell us and the practical work involved in making a diet adequate, enjoyable and sustainable. It is written for adults considering everyday eating patterns.
Identify the foods, nutrient proportions or eating times the approach alters.
When a usual food disappears, plan dependable sources of its useful nutrients.
Consider energy, enjoyment, health, training, cost and the people you eat with.
Different diets change different parts of eating
These approaches can overlap. Someone can eat vegetarian meals with a moderate carbohydrate intake and a conventional meal schedule. Another person may combine vegan eating with a restricted eating window. Combining labels increases the number of choices to plan around; it does not automatically improve the outcome.
| Approach | Main feature | A central planning question |
|---|---|---|
| Vegetarian | Excludes meat, poultry and fish; some forms include eggs or dairy. | Which protein and micronutrient sources replace excluded foods? |
| Vegan | Excludes foods of animal origin, including dairy, eggs and honey. | Is there a dependable B12 plan and adequate provision of other nutrients? |
| Low-carbohydrate | Reduces carbohydrate intake; definitions and degrees of restriction vary. | What replaces the carbohydrate, and how does the pattern support daily needs? |
| Ketogenic | Restricts carbohydrate sufficiently to promote nutritional ketosis. | How will food variety, blood lipids, symptoms and training demands be considered? |
| Intermittent fasting | Restricts eating times or reduces intake on selected days. | Can the available meals provide enough energy and nutrients comfortably? |
Plant-based is a broader, less precise phrase. It may describe a fully vegan diet or one that gives plant foods a larger role while retaining some animal foods. A person who includes fish but avoids other meat is usually described as pescatarian.
Medical diets for a diagnosed condition have additional requirements. A general comparison of eating patterns cannot replace a plan designed for a specific treatment.
Adequate nutrition matters within every pattern
WHO identifies adequacy, balance, moderation and diversity as foundations of a healthy diet. Its guidance gives a central place to vegetables, fruit, pulses and whole grains, with attention to fat quality, free sugars and salt.[1]
A diet should provide enough energy for the person, meaningful protein sources, essential fats and the vitamins and minerals needed over time. A list of permitted foods is only the beginning of that work.
Look at what takes the place of an excluded food
Replacing meat with lentils or tofu produces a different meal from simply removing the main protein component. Replacing dairy with a fortified drink differs from choosing an unfortified drink with little protein. Reducing sugary drinks is a different change from removing beans and fruit.
Ask what the replacement contributes: protein, fibre, calcium, iron, energy, enjoyment or convenience. These details often tell you more than the diet's name.
Make room for ordinary food and ordinary life
Frozen vegetables, canned beans, bread, tofu and fortified foods can make an adequate routine easier. Processing describes many different operations; a useful product does not have to be prepared entirely from scratch.
The aim is an eating pattern that works across real days: work, travel, training, celebrations and times when cooking is difficult. A plan that leaves someone persistently hungry, exhausted or unable to join ordinary meals needs review.
Plant-based eating can support health when it is well planned
Lacto-ovo vegetarian diets include dairy and eggs. Lacto-vegetarian diets include dairy but exclude eggs; ovo-vegetarian diets include eggs but exclude dairy. Vegan diets use foods of plant origin and other suitable non-animal ingredients.
The Academy of Nutrition and Dietetics' 2025 position paper states that appropriately planned vegetarian and vegan patterns can be nutritionally adequate and offer health benefits in adults.[2] The condition—appropriate planning—deserves as much attention as the dietary label.
What intervention studies show
In an eight-week randomised study of identical twins, a healthy vegan diet produced a greater reduction in LDL cholesterol than the healthy omnivorous comparison diet.[3] This was a small, supported dietary intervention measuring risk factors, not a trial of heart attacks or lifelong health.
A favourable blood result does not make every food sold as vegan equivalent. Coconut-rich desserts, low-protein cheese alternatives and meals built mainly around refined snacks have different nutritional roles from beans, vegetables, whole grains and substantial protein foods.
Values can shape a thoughtful choice
People may choose these patterns for animal welfare, faith, culture or environmental reasons without making weight loss a goal. Those reasons can remain central while nutritional needs are addressed deliberately.
Build a collection of meals you like. Familiar ingredients such as oats, buckwheat, potatoes, beans, peas, lentils, cabbage, berries and seeds can provide a starting point alongside tofu, dairy or eggs where the chosen pattern includes them.
Plan substantial protein sources through the day
Useful plant protein foods include beans, lentils, chickpeas, soy foods and seitan where gluten is suitable. Nuts, seeds and grains contribute too, though a small garnish of nuts may provide much less protein than a substantial serving of legumes or tofu.
A varied, adequate diet can supply the essential amino acids. There is usually no need to pair a particular grain and bean at every meal. Regularly including a range of protein foods is a more practical starting point.
What the training evidence means
A twelve-week comparison of habitual vegan and omnivorous young men found similar gains in measured muscle size and strength when both groups completed resistance training and consumed matched, adequate protein, supported by soy or whey supplementation.[4] Participants were not randomly assigned to become vegan or omnivorous.
The study supports the feasibility of muscle development with a carefully organised plant-based diet. It does not establish that every plant food, serving size or low-protein menu will produce the same result.
Make the protein component easy to identify
A breakfast might include a protein-rich soy yoghurt with oats, a lunch could centre on lentils or beans, and an evening meal might use tofu or tempeh. Check the actual product: plant yoghurts and drinks differ considerably in protein content.
Protein powder can be a convenient ingredient when food alone is awkward, especially around a busy schedule. It is one way of meeting a need, not a requirement for every person.
Enough total food matters as well. A very bulky, high-fibre menu can feel filling before it supplies enough energy for a highly active person. Adjust portions, food choices and meal frequency so training is supported by nourishment.
B12 needs a plan; other nutrients need attention too
The German Nutrition Society's 2024 position supports a well-planned vegan diet for the general population provided that B12 is supplemented and potentially critical nutrients are adequately supplied.[5]
Vitamin B12: make the source reliable
For a vegan diet, establish a dependable B12 supplement plan. Fortified foods can contribute, but check that B12 is actually added and that the amounts and frequency fit the plan. Vegetarians who eat little dairy or eggs can also have inadequate intake.[6]
Arrange appropriate advice about the product, dose and follow-up, particularly if a deficiency is possible. Do not rely on unfortified plant foods or wait for symptoms to decide whether B12 matters.
| Nutrient | Food or supplement options | What to check |
|---|---|---|
| Iron | Beans, lentils, tofu, seeds and appropriately fortified foods. | Plant iron is absorbed differently from haem iron. Vitamin-C-rich food with a meal can improve non-haem iron absorption.[7] |
| Calcium | Calcium-fortified drinks or yoghurts, calcium-set tofu, and suitable vegetables such as broccoli or kale. | Check fortification and the tofu's calcium content. Spinach is not a dependable main source because its calcium is poorly absorbed.[8] |
| Iodine | Iodised salt within usual salt limits; suitably fortified foods or an appropriate supplement when needed. | Ordinary sea salt and plant drinks may supply little iodine. Seaweed content varies greatly, and some products provide excessive amounts.[9] |
| Vitamin D | Fortified foods and supplements appropriate to individual needs and local guidance. | Skin production varies with season and other factors. Sun exposure is not a dependable year-round plan for everyone.[10] |
| Omega-3 fats | Ground flaxseed, chia, walnuts and rapeseed oil provide ALA. Algal products can supply DHA and, in some products, EPA. | Conversion of ALA to EPA and DHA is limited. Consider the actual fatty acids and amounts a product supplies.[11] |
| Other nutrients | Varied legumes, whole grains, nuts, seeds and other suitable foods contribute zinc, selenium and additional nutrients. | A very narrow menu can leave several gaps. Review the whole pattern, especially when further food groups are excluded.[5] |
Supplements should solve an identified nutritional need. Iron, iodine and other nutrients can cause harm in excessive amounts. A general multivitamin does not necessarily supply enough of a missing nutrient, and taking several products can create unintended overlap.
Blood tests can be useful when chosen for a relevant question, such as possible iron or B12 deficiency. Their selection and interpretation should reflect dietary intake, symptoms, health history and the supplements already being used.
Understand the restriction and the change in fuel use
Low-carbohydrate covers a range of eating patterns. There is no single carbohydrate cut-off used consistently across research and everyday advice. A modest reduction can still leave substantial room for legumes, fruit and whole grains.
A ketogenic diet is more restrictive and aims to produce sustained nutritional ketosis. Some protocols use around 20–50 grams of carbohydrate per day, but the amount required varies. The percentage of energy from fat also depends on the particular plan.
Ketosis changes the mixture of fuels
With carbohydrate strongly restricted, the liver produces more ketones from fat. Tissues use a changing mixture of fatty acids, ketones and glucose. The body continues to make glucose for functions that require it; it does not switch every tissue to ketones.[12]
Nutritional ketosis describes a metabolic state. A ketone measurement does not, by itself, establish fat loss, good nutrition, improved cognition or better performance.
Look at the foods behind the numbers
A lower-carbohydrate meal could include tofu, fish, eggs or another suitable protein food, vegetables, nuts and olive or rapeseed oil. Another could rely heavily on butter, cream and processed meat. Similar carbohydrate totals can conceal important differences in food quality.
Keep the purpose clear. If a gentler change meets the intended goal, there may be little practical reason to exclude additional foods solely to reach a more restrictive label.
More fat oxidation does not automatically mean more body-fat loss
Fat used for fuel can come from meals. Body-fat loss also depends on the overall energy balance and the body's responses.
In a controlled inpatient study of seventeen men, switching to an equal-calorie ketogenic diet with protein held constant increased fat use but did not accelerate body-fat loss.[13] The short study helps separate fuel selection from a claim of an automatic fat-loss advantage.
Interpret early scale changes carefully
Carbohydrate restriction can reduce glycogen and its associated water. Early scale changes therefore need not represent body-fat loss alone; some weight can return with carbohydrate replenishment.
Over twelve months, the DIETFITS trial found no significant difference in average weight loss between its healthy lower-fat and lower-carbohydrate approaches.[14] The lower-carbohydrate arm was not a test of sustained strict ketosis.
Different blood markers can move in different directions
In the Keto-Med crossover trial involving people with prediabetes or type 2 diabetes, the ketogenic and Mediterranean-style diets did not differ significantly in HbA1c after their respective phases. The ketogenic phase lowered triglycerides more but produced higher LDL cholesterol and lower intake of fibre and some nutrients.[15]
A change in triglycerides should therefore be considered alongside LDL cholesterol and the wider health picture. If using a restrictive diet for a medical goal, agree with a clinician which outcomes to review and what would prompt a change.
Some people find carbohydrate reduction helpful for appetite or meal planning. Others find the restrictions difficult to sustain. Both the nutritional result and the effort required to maintain it belong in the decision.
Performance depends on the task and the available fuel
Training goals change what a diet needs to provide. A comfortable walk, repeated hard intervals and a long competitive event place different demands on fuel availability, digestion and recovery.
In a controlled study of elite race walkers, a ketogenic low-carbohydrate diet markedly increased fat oxidation while worsening exercise economy and preventing the performance improvement seen with the higher-carbohydrate approaches.[16] This does not settle every question about endurance sport, but it challenges the assumption that burning more fat necessarily improves performance.
Protect the ability to train and recover
Review the quality of your sessions, recovery, appetite and ability to eat enough. A change that consistently makes the intended training harder to complete may need adjustment even if a ketone number or body-weight target looks favourable.
Strength and muscle development also require appropriate training and adequate protein and energy. Adjust carbohydrate intake to the programme's demands, food preferences and medical needs.
Low energy availability can affect any athlete
The IOC describes relative energy deficiency in sport as harmful health and performance effects arising when energy availability is inadequate in relation to exercise demands. It can affect female and male athletes.[17]
Persistent fatigue, disrupted menstrual function where applicable, recurrent injuries or declining performance deserve review. These problems can develop with vegan, ketogenic, fasting or conventional eating patterns if intake does not meet the person's needs.
A sports dietitian can help when food exclusions, high training demands and difficult schedules make the plan complicated. The useful outcome is sufficient, practical nourishment for the work you are doing.
Eating schedules differ in both timing and restriction
Intermittent fasting is an umbrella term for several approaches. Some mainly change the daily eating window; others deliberately reduce energy intake on selected days. Studies of one arrangement cannot automatically answer questions about all the others.
Time-restricted eating
This places meals and energy-containing drinks within a daily window. A “16:8” schedule, for example, describes sixteen hours without caloric intake and an eight-hour eating window. It does not specify the quality or quantity of the food, and it does not inherently require skipping breakfast.
An earlier or later window may fit different work, sleep and family arrangements. The practical question is whether the schedule allows adequate meals, suitable training fuel and a comfortable daily routine.
Selected lower-intake days
In a 5:2 pattern, two days have substantially reduced intake. Alternate-day approaches alternate lower-intake or fasting days with other days. A 4:3 approach uses three lower-intake days. Exact protocols vary, including whether a “fast” allows some food.
These approaches create more substantial changes than simply keeping regular meal times. Their research results depend partly on the prescribed intake, adherence and support provided.
One meal a day
OMAD compresses daily eating into one meal. That can make it difficult to distribute protein, obtain enough energy comfortably or fit food around training. A very narrow eating window is not necessary to explore a more regular eating routine.
This guide describes the patterns so they can be understood and compared. It does not prescribe prolonged or severe fasting.
Some approaches help some people; the comparison matters
Changing eating times can change how much someone eats, how easy meals are to organise and whether late snacks remain part of the day. A study may therefore be testing several changes together, even when its headline focuses on the clock.
Adding a daily window is not always an extra benefit
In a twelve-month trial of adults with obesity, time-restricted eating added to calorie restriction did not produce a statistically significant additional weight-loss benefit compared with calorie restriction alone.[18] That result concerns the particular programme and population studied.
Another protocol produced a different result
A 2025 trial found modestly greater weight loss with a 4:3 intermittent-fasting approach than with daily calorie restriction after twelve months. Both groups received an intensive behavioural weight-management programme.[19]
This supports a specific option within substantial support; it does not show that any fasting schedule will outperform any conventional diet. The study's prescribed weekly energy deficits were similar, while how participants followed the plans could differ.
Judge more than the weight change
For someone who wants to reduce body weight, a schedule may be useful if it makes an appropriate eating pattern easier. For another person, the same rule may cause headaches, persistent hunger, overeating later or difficulty meeting nutritional needs.
Weight loss is not the only possible goal, and it is not appropriate for everyone. Consider nutritional adequacy, health measures where relevant, energy, sleep, social meals and the amount of attention the routine demands.
There is no need to continue a schedule simply because it has a name. A conventional arrangement of meals and snacks can remain a suitable choice.
Autophagy research does not provide a fasting countdown
Autophagy is cellular maintenance: cells break down and recycle their components. Activity varies across tissues and circumstances.
An exploratory 2025 study measured this process in blood immune cells. Six-month changes differed between intermittent time-restricted eating and standard care, partly reflecting a decline in controls. The fasting group did not differ significantly from calorie restriction or show a significant increase from its own baseline.[20]
These findings do not establish longer human life or an hour at which fasting begins to deliver a health benefit.
Health conditions and nutritional vulnerability change the decision
Food restriction can interact with health conditions, treatment and existing nutritional needs. Address those interactions before making a substantial change, especially when several restrictions would be combined.
Diabetes and glucose-lowering treatment
Skipping meals, fasting or markedly reducing carbohydrate can increase the risk of low blood glucose with insulin and some other diabetes medicines.[21] Discuss the plan with the clinician managing treatment; do not adjust medication doses on your own.
SGLT2 inhibitors require particular care because restricted food intake and dehydration can contribute to ketoacidosis risk, sometimes without very high glucose levels.[22] Nutritional ketosis and ketoacidosis are different states; the latter is a medical emergency.
Vomiting, abdominal pain, unusual deep or rapid breathing, or marked confusion during a restrictive diet—especially with diabetes or SGLT2 treatment—require urgent medical assessment. Do not dismiss serious symptoms as an expected adjustment to keto.
Life stages and other food restrictions
Pregnancy, breastfeeding, older age with nutritional vulnerability and growing years need particular planning. The DGE recommends qualified nutrition counselling for vulnerable groups considering vegan diets because the evidence and consequences of inadequate provision require extra care.[5]
Kidney disease, gastrointestinal conditions, a history of bariatric surgery or several food allergies can also change suitable sources and amounts. For someone with coeliac disease, for example, seitan is unsuitable because it is made from wheat gluten.
Protect a workable relationship with food
If restriction is linked with an eating disorder, recurrent loss of control around food or significant distress, seek advice that supports adequate, regular nourishment. Adding a tighter eating window or more exclusions may make the problem harder to manage.
Professional support should help you meet your needs and retain meaningful choice. It should be specific to the problem you are trying to solve.
Build from useful ingredients and realistic preparation
Begin with a few meals you enjoy and can obtain reliably. Identify a substantial protein component, a source of energy suited to your needs, vegetables or fruit, and appropriate fats. A single plate does not have to provide every nutrient, but the pattern across days needs to cover them.
A plant-based meal
Lentil and vegetable stew with buckwheat, a rapeseed-oil dressing and a side you enjoy. Include dependable calcium, B12 and other relevant sources elsewhere in the daily plan.
A vegetarian meal
Beans with roasted vegetables and potatoes, accompanied by yoghurt or another suitable calcium source. Eggs, tofu or other protein foods can offer variety across meals.
A lower-carbohydrate meal
Tofu, fish or eggs with a generous selection of vegetables, olive oil and nuts or seeds. The carbohydrate portion can be adjusted to the intended pattern and the person's needs.
These are meal ideas, not nutritionally complete daily menus or guaranteed ketogenic recipes. Portion size, product composition and the rest of the day still matter.
Check the foods that replace your usual staples
For plant drinks and yoghurts, compare protein, calcium, B12, vitamin D and iodine where declared. Fortification differs across products and countries; neither the word “plant” nor “organic” guarantees that a nutrient has been added.
Follow product instructions, including shaking a fortified drink where directed. Compare the amount in the portion you actually use rather than assuming a small splash provides a full serving's nutrients.
Prepare for a busy day
Keep a few reliable options available: canned pulses, frozen vegetables, suitable grains or other staples, a protein food and ingredients for a quick sauce. Choose combinations that match your dietary requirements and available storage.
When arranging a shared meal, discuss what you can eat and offer a simple option. Flexibility can concern preparation, ingredients and timing while respecting ethical, religious or medical boundaries that matter to you.
A five-step process for finding a workable approach
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Name the purpose.
Identify whether the change concerns personal values, a health outcome, meal organisation, training or another meaningful goal. Decide what a useful result would look like.
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Map the nutritional changes.
List the foods or meals that would disappear and their replacements. Pay particular attention to dependable B12 provision in a vegan pattern and to adequate energy when meals are reduced.
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Check the fit with health and daily life.
Consider medication, existing restrictions, cooking facilities, budget, family meals and activity. Obtain specific advice where these factors complicate the plan.
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Make the routine concrete.
Choose several meals and a shopping list. Plan food around the day you actually have, including the times when you are tired or away from home.
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Review the whole response.
Look at energy, comfort, enjoyment, training and relevant health measures. Keep what works and change what leaves needs unmet.
Use monitoring to answer a question
A short food record can reveal a missing protein source or an eating window that repeatedly prevents adequate meals. A clinically indicated blood test may help assess a particular nutrient or lipid concern. Monitoring is most useful when it leads to a clear decision.
There is no requirement to count every calorie or measure ketones for general healthy eating. Tracking can be helpful for some people and burdensome for others. Choose the least complicated method that answers the relevant question.
Give change a practical meaning
Maintaining adequate intake, enjoying meals and having more energy for ordinary life can all be worthwhile outcomes. If the current approach makes these harder, reviewing it is a sensible response to new information.
A dietary pattern is something you use. It can be revised as health, knowledge, preferences and circumstances change.
Clear answers about special diets
Is a vegan diet automatically healthier?
No. A well-planned vegan pattern can support health, while a narrow or inadequately supplemented pattern can leave important gaps. Look at the actual foods, nutrient provision and individual needs.
Do vegans really need to plan B12?
Yes. Establish a dependable supplement plan and check the contribution from fortified foods. Ordinary unfortified plant foods are not a reliable way to meet the need.
Can I build muscle with plant protein?
Yes, with appropriate resistance training and adequate protein and energy. Choose substantial protein sources consistently; the usefulness of a meal depends on its actual contents and portions.
Are low-carbohydrate and ketogenic diets the same?
No. Low-carbohydrate describes a broad range of intakes. A ketogenic approach restricts carbohydrate sufficiently to promote nutritional ketosis and usually requires more extensive exclusions.
Does a higher ketone reading mean faster fat loss?
No. Ketones reflect aspects of fuel availability and use. They do not measure how much body fat is being lost or establish the overall quality of the diet.
Does fasting work better than regular meals?
It depends on the protocol, comparison and person. Some supported fasting programmes help with weight management; others show little additional benefit over conventional approaches. Adequate regular meals remain a valid option.
Must I skip breakfast to practise time-restricted eating?
No. An eating window can be placed earlier or later. Its timing needs to fit nutritional needs, treatment, training and daily responsibilities.
When does fasting switch on autophagy?
A universal fasting countdown is not established. Measuring cellular recycling in one tissue does not demonstrate a lifespan benefit.
Can I combine vegan eating, keto and fasting?
These patterns can overlap, but each extra restriction makes meal planning and adequate intake more demanding. First establish what purpose the combination serves and whether a simpler arrangement can meet the same needs.
Do I need a large collection of supplements or routine blood panels?
No. Use supplements for dependable nutrient provision or a specific identified need, and choose tests that answer a relevant clinical question. B12 planning in a vegan diet deserves particular attention.
Sources and the limits of general advice
Evidence and guidance checked: 5 September 2026. The sources include current professional guidance, controlled human studies and official nutrient information. Their notes explain the populations and outcomes studied.
A short change in a blood marker, a year of weight management and long-term disease prevention answer different questions. Meal examples in this guide are editorial illustrations, and individual nutritional requirements still need an appropriate plan.
- World Health Organization. Healthy diet. Public health guidance, updated 26 January 2026.General foundations for dietary adequacy, balance, moderation and variety; not a personalised diet prescription. Return to text ↑
- Raj S, et al. Vegetarian Dietary Patterns for Adults. Journal of the Academy of Nutrition and Dietetics. 2025;125(6):831–846.e2. DOI: 10.1016/j.jand.2025.02.002.Title shortened. Current professional position on appropriately planned vegetarian and vegan diets in adults; its scope should not be extended automatically to every life stage. Return to text ↑
- Landry MJ, Ward CP, Cunanan KM, et al. Cardiometabolic Effects of Omnivorous vs Vegan Diets in Identical Twins. JAMA Network Open. 2023;6(11):e2344457. DOI: 10.1001/jamanetworkopen.2023.44457.Title shortened. Eight-week randomised trial in 22 twin pairs, with meals provided initially. The LDL finding concerns a risk marker, not demonstrated prevention of clinical events. Return to text ↑
- Hevia-Larraín V, Gualano B, Longobardi I, et al. High-Protein Plant-Based Diet Versus a Protein-Matched Omnivorous Diet to Support Resistance Training Adaptations. Sports Medicine. 2021;51:1317–1330. DOI: 10.1007/s40279-021-01434-9.Title shortened. Twelve weeks of training in habitual vegan and omnivorous young men with protein matched using soy or whey. Diet-group membership was not randomly assigned. Return to text ↑
- German Nutrition Society (DGE). Update of the DGE position on vegan diet. Ernährungs Umschau International. 2024;71(7):60–84.Position on B12 supplementation, adequate nutrient provision and qualified counselling for nutritionally vulnerable groups. Return to text ↑
- National Institutes of Health, Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. Official nutrient guidance; accessed September 2026.Food sources, fortification, supplementation and deficiency risk. A treatment regimen for deficiency requires individual assessment. Return to text ↑
- National Institutes of Health, Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. Official nutrient guidance; accessed September 2026.Sources and absorption of iron, including the effect of vitamin C on non-haem iron absorption. Return to text ↑
- National Institutes of Health, Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals. Official nutrient guidance; accessed September 2026.Food sources and differences in absorption. Fortification and calcium content must be checked for the product used. Return to text ↑
- National Institutes of Health, Office of Dietary Supplements. Iodine: Fact Sheet for Health Professionals. Official nutrient guidance; accessed September 2026.Sources, dietary shortfalls and excessive intake; iodine content of seaweed can vary substantially. Return to text ↑
- National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. Official nutrient guidance; accessed September 2026.Food and supplemental sources, and factors influencing skin production. Use individual circumstances and local guidance for a supplement plan. Return to text ↑
- National Institutes of Health, Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. Official nutrient guidance; accessed September 2026.Distinguishes ALA, EPA and DHA, their sources and the limited conversion of ALA to longer-chain forms. Return to text ↑
- Kolb H, Kempf K, Röhling M, et al. Ketone bodies: from enemy to friend and guardian angel. BMC Medicine. 2021;19:313. DOI: 10.1186/s12916-021-02185-0.Physiology review cited for ketone production and the continued use of multiple fuels. Mechanistic proposals do not establish long-term benefits of a ketogenic diet. Return to text ↑
- Hall KD, Chen KY, Guo J, et al. Energy expenditure and body composition after an isocaloric ketogenic diet. American Journal of Clinical Nutrition. 2016;104(2):324–333. DOI: 10.3945/ajcn.116.133561.Title shortened. Controlled inpatient study in 17 men; diets were given sequentially with calories and protein held constant. Greater fat oxidation did not accelerate body-fat loss. Return to text ↑
- Gardner CD, Trepanowski JF, Del Gobbo LC, et al. Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss: the DIETFITS Trial. JAMA. 2018;319:667–679. DOI: 10.1001/jama.2018.0245.Title shortened. Twelve-month randomised trial in 609 adults without diabetes. Average weight loss did not differ significantly; the lower-carbohydrate intervention was not sustained strict ketosis. Return to text ↑
- Gardner CD, Landry MJ, Perelman D, et al. Ketogenic versus Mediterranean diets: the Keto-Med randomised crossover trial. American Journal of Clinical Nutrition. 2022;116(3):640–652. DOI: 10.1093/ajcn/nqac154.Title abbreviated. Participants with prediabetes or type 2 diabetes followed each diet for 12 weeks. Similar HbA1c results accompanied differing lipid and nutrient outcomes. Return to text ↑
- Burke LM, Ross ML, Garvican-Lewis LA, et al. Low carbohydrate, high fat diet and exercise economy in elite race walkers. Journal of Physiology. 2017;595(9):2785–2807. DOI: 10.1113/JP273230.Title abbreviated. Short controlled training study in elite race walkers. Its results should not be treated as a test of every sport or every low-carbohydrate approach. Return to text ↑
- Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 IOC consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine. 2023;57:1073–1097. DOI: 10.1136/bjsports-2023-106994.Title shortened. Consensus on problematic low energy availability and its health and performance effects in female and male athletes. Return to text ↑
- Liu D, et al. Calorie Restriction with or without Time-Restricted Eating in Weight Loss. New England Journal of Medicine. 2022;386(16):1495–1504. DOI: 10.1056/NEJMoa2114833.Twelve-month randomised trial in 139 adults with obesity. Adding an eight-hour eating window did not yield a statistically significant additional weight-loss benefit. Return to text ↑
- Catenacci VA, et al. The Effect of 4:3 Intermittent Fasting on Weight Loss at 12 Months. Annals of Internal Medicine. 2025;178(5):634–644. DOI: 10.7326/ANNALS-24-01631.Title shortened. Randomised trial in 165 adults. The modest advantage for 4:3 fasting occurred within an intensive behavioural programme in both groups. Return to text ↑
- Bensalem J, Teong XT, Hattersley KJ, et al. Intermittent time-restricted eating may increase autophagic flux in humans: an exploratory analysis. Journal of Physiology. 2025;603(10):3019–3032. DOI: 10.1113/JP287938.Exploratory analysis of blood immune cells. The six-month comparison does not establish whole-body effects, an optimal fasting duration or increased human lifespan. Return to text ↑
- National Institute of Diabetes and Digestive and Kidney Diseases. Low Blood Glucose (Hypoglycemia). Official patient guidance; accessed September 2026.Explains how inadequate carbohydrate intake, skipped meals or fasting can interact with insulin and some other glucose-lowering medicines. Return to text ↑
- European Medicines Agency. EMA confirms recommendations to minimise ketoacidosis risk with SGLT2 inhibitors for diabetes. Safety communication, 26 February 2016; accessed September 2026.Restricted food intake and dehydration are relevant risk factors. Ketoacidosis can occur without markedly elevated glucose and requires urgent treatment. Return to text ↑