Nutrition briefing
Fasting as a curative diet
Fasting means reducing some or all of your food intake. It is a form of caloric restriction, and a growing body of research suggests that, done correctly, it activates powerful cellular adaptation mechanisms that promote longevity and wellbeing and help prevent chronic disease. Done incorrectly, it carries real risks, so it is best done under the guidance of a healthcare professional.
8 key principles for therapeutic fasting
Current research suggests there are eight principles to follow when using fasting as a curative diet. You do not have to nail all eight at once. Following as many as possible gives the best balance of benefit and safety.
Fast intermittently on non-consecutive days
Evidence suggests it is best to fast on non-consecutive days for 1 to 4 days per week, with the best effects seen after about 4 weeks. An intermittent fasting program is generally recommended for up to 12 weeks at a time. Have regular health reviews during the fasting period.
Eat on fasting days, just reduce calories
Complete abstinence from food is not ideal. Eating some calories on fasting days is safer and more practical, especially for busy people with high energy demands. It improves compliance and reduces the risk of nutrient and electrolyte depletion. Aim for roughly 500 to 600 kcal on fasting days, following Mediterranean-style guidelines with smaller portion sizes, and eat normally on non-fasting days.
Eat a healthy, whole food diet on every day
It is critical to eat a healthy, wholefood diet on both fasting and non-fasting days so nutrient levels are maintained and general wellbeing is supported. A Mediterranean-style diet is well researched for its metabolic, neuroprotective and cardiovascular benefits, so it is the suggested pattern throughout a fasting program.
Allow at least 12 hours of fasting per day, every day
Fasting overnight gives the body time to heal and activate rejuvenation processes, and lets the metabolism start using its own reserves as fuel. Narrowing the eating window to less than 12 hours per day has been shown to reduce appetite, improve weight loss and significantly improve overall wellbeing. Apply this on both fasting and non-fasting days.
This may not be appropriate for those with blood sugar fluctuations such as hypoglycaemia.
Aim for big breakfasts and smaller dinners
When you eat is as important as what you eat. Eating the largest meal at breakfast, having a light early dinner, and fasting overnight activates neuroprotective and antioxidant mechanisms. Eating the largest meal in the evening, or eating late at night, increases inflammation and metabolic challenges and leads to weight gain. Aim to take in most of your calories early in the day, on both fasting and non-fasting days.
Eat plenty of non-starchy, above-ground vegetables
Compliance and health benefits improve when unlimited amounts of non-starchy, above-ground vegetables are eaten during a fasting program, especially on fasting days. These vegetables are high in minerals and micronutrients and high in fibre, which adds to feelings of fullness. Restricting protein while increasing vegetable intake on fasting days may also support longevity and cellular rejuvenation.
Keep exercising during the program
Weight loss from calorie restriction is often accompanied by losses in muscle and bone, but exercising during a fasting program, resistance training in particular, helps prevent that. Aim for some resistance training at least 3 times per week on non-fasting days. Morning exercise may be best, as there is also research suggesting better metabolic benefits from exercising before meals, such as before breakfast.
Provide some supplementation support
Reduced food intake can mean reduced nutrient intake for some people. Fasting and weight loss also tend to cause a loss of electrolyte minerals such as magnesium, potassium, calcium and sodium, and can drive a mild metabolic acidosis through the production of keto-acids. Supporting healthy metabolic function with nutritional supplementation is therefore important. See the support options below.
Nutritional support options during fasting
Different challenges of a fasting program call for different prescribing considerations. The table below maps common issues to the support that may help. Discuss any supplementation with your practitioner first.
| Fasting challenge | Prescribing consideration |
|---|---|
| Electrolyte loss | Consider alkalising minerals such as potassium, magnesium, calcium and sodium in a citrate form. |
| Nutrient loss | Consider a multi-nutrient formula with activated B group vitamins, particularly B1 and vitamin C. Check nutrient status before the program. |
| Slowing metabolism | Add exercise into the program. Check thyroid function and provide thyroid support if needed. |
| Mild metabolic acidity | Consider alkalising minerals such as potassium, magnesium, calcium and sodium in a citrate form. |
| Liver detox challenges | Support the liver phases with herbs such as Milk thistle and Schisandra. |
| Stress and/or insomnia | Provide sleep and calming herbs such as Magnolia, Zizyphus, Passionflower and Lavender. |
| Hunger and/or poor compliance | Allow up to 2 weeks to habituate to the program. Introduce the principles slowly, adding one more every 3 to 7 days. |
| Orthostatic hypotension (low blood pressure) | Consider electrolyte supplementation and hydration. |
| Muscle preservation | Maintain adequate protein intake. Add fish oils and vitamin D. Consider alkalising minerals such as potassium, magnesium, calcium and sodium in a citrate form. |
| Bone preservation | Maintain adequate calcium intake. Add vitamin D. Consider alkalising minerals such as potassium, magnesium, calcium and sodium in a citrate form. |
An example fasting program
Program length
4 to 12 weeks, with regular practitioner consultations to monitor nutrient status, symptoms and compliance.
Fast frequency
2 to 3 days per week on non-consecutive days. For example, fast on Monday and Thursday, or on Monday, Wednesday and Friday each week.
Plan for fasting days
- Reduce calories to 500 to 600 kcal per day following a Mediterranean-style diet, or do not count calories but make all food intake exclusively non-starchy, above-ground vegetables, with small amounts of fats such as olive or coconut oil.
- Eat 2 to 3 small meals per day, roughly one third to half of a normal portion. Make breakfast the largest portion.
- Fast overnight, meaning no eating after 6pm, for around 14 hours from the last meal until the next day at 8am, drinking only non-caloric beverages such as herbal teas and water.
- Exercise first thing in the morning, before eating.
- Supplement with alkalising minerals and individual nutrients as required.
Plan for non-fasting days
- Fast overnight for at least 12 hours, for example from 7pm to 7am.
- Eat 2 to 3 meals per day of normal portion size. Make breakfast the largest portion.
- Follow a Mediterranean-style diet with lots of non-starchy, above-ground vegetables.
- Exercise first thing in the morning, before eating.
- Supplement with alkalising minerals and individual nutrients as required.
Other suggestions
Forward planning and preparing healthy daily meals for both fasting and non-fasting days makes the whole program more successful. It can also be a good idea to start slowly and introduce the key principles one at a time.
What to eat and what to avoid
The Mediterranean-style diet
Eat mostly eat
Vegetables, fruits, nuts, seeds, legumes, whole grains, herbs, spices, fish, seafood and extra virgin olive oil. Eating organic wherever possible reduces the risk of chemical toxicity. The pattern can be modified for vegetarian or vegan preferences.
Avoid or minimise limit
Sugar-sweetened beverages, artificial sweeteners, added sugars, processed meat, refined grains, refined oils and other highly processed foods.
Non-starchy, above-ground vegetables
On fasting days, lean on non-starchy, above-ground vegetables. These can be eaten freely. Starchy and below-ground vegetables are best avoided on fasting days.
Eat freely eat
Spinach, lettuce, asparagus, cucumber, zucchini, cauliflower, broccoli, capsicum, green beans, brussels sprouts, tomato, kale, eggplant, cabbage, avocado, celery and olives.
Avoid on fasting days avoid
Potato, carrot, onion, parsnip, sweet potato, celeriac, beetroot and pumpkin.
Frequently asked questions
What is therapeutic fasting?
Therapeutic fasting is a structured pattern of voluntary calorie reduction used to support cellular repair, metabolic flexibility and chronic-disease prevention, rather than complete starvation. This guide frames it around eight key principles and an example program, typically fasting on one to four non-consecutive days a week, eating around 500 to 600 kcal of mostly Mediterranean-style food on fasting days, and eating normally otherwise, run over about 4 to 12 weeks with regular practitioner review.
How many calories do you eat on a fasting day?
On fasting days the guide suggests around 500 to 600 kcal rather than zero, ideally from Mediterranean-style food with unlimited non-starchy, above-ground vegetables to add fibre and promote fullness. On non-fasting days you eat normally. It also recommends a daily fasting window of at least 12 hours every day, for example a bigger breakfast and a light early dinner, which the resource links to better appetite control and weight loss.
Is fasting safe and who should be cautious?
The guide presents fasting as best done with regular practitioner review over about 4 to 12 weeks, and includes supportive measures like electrolytes and certain B and C vitamins, plus resistance training on non-fasting days to protect muscle and bone. Fasting is not appropriate for everyone, so professional guidance matters, especially for anyone who is underweight, pregnant or breastfeeding, has a chronic illness or eating disorder history, or takes medication.
Reviewed by Rohan Smith, BHSc Nutritional Medicine · Elemental Health & Nutrition, Adelaide. Last reviewed 13 June 2026.
Important: This summary is general information, not personalised medical advice, diagnosis, or a treatment protocol. Speak with a qualified practitioner about your individual situation. Book a consultation →