Fasting can be a meaningful spiritual practice, and for some healthy adults a short, well-planned fast is safe. It isn’t right for everyone, the evidence that it beats ordinary healthy eating for weight loss is limited, and the way you start and end a fast matters as much as the fast itself. This guide covers why people fast, who should skip it, and how to prepare, fast and break the fast sensibly.
Two reasons people fast
People fast for different reasons, and being clear about yours shapes how you do it.
- Spiritual fasting is usually about focus: setting aside food for a set time to pray, reflect, seek guidance, practise self-discipline or care for others (some people donate the money they would have spent on meals). The point is attention and humility, not a number on the scale.
- Health-motivated fasting, often called intermittent fasting, is about the timing of meals: eating within a limited window each day, or eating very little on certain days.
The two can overlap, but they pull in different directions. If a spiritual fast starts to feel like a diet in disguise, or if the main feeling is pride or anxiety about food, it’s worth stepping back.
What the evidence says about health benefits
The research is less settled than many headlines suggest. The U.S. National Institute on Aging describes common fasting patterns, such as time-restricted eating and alternate-day fasting, and concludes that there is insufficient evidence to recommend any type of calorie-restriction or fasting diet, especially for older adults, and advises talking with your healthcare provider before making significant changes.
Harvard’s Nutrition Source reviewed the weight-loss trials and found that intermittent fasting generally produced weight loss similar to ordinary calorie reduction, not better, and that strong recommendations can’t be made yet. It also notes that long periods without food can set some people up to overeat when food comes back.
So a fast may help you feel more in charge of your eating, or simply give structure to a busy day. It isn’t a shortcut, and the meals you eat around it still do most of the work.
Who should not fast, or should get medical advice first
The Harvard review lists groups for whom intermittent fasting is not appropriate. Use this as your starting checklist:
- People with diabetes, especially those on insulin or other glucose-lowering medicines
- People who take medicines that must be taken with food
- Anyone with a current or past eating disorder
- Pregnant or breastfeeding women
- Children and teens who are still growing
Also check with your doctor if you have heart or kidney disease, low blood pressure, a history of fainting, gout, or you’re recovering from illness or surgery. Many faith communities explicitly excuse the sick, pregnant, nursing, young and elderly from fasting, and you can follow that example without guilt.
If fasting tends to lead to bingeing, or you notice yourself thinking about food constantly, losing control around food, or feeling intense guilt after eating, skip fasting from food. Choose a different form of fasting (see below) and talk with your healthcare provider. NEDIC (the National Eating Disorder Information Centre) offers free support across Canada.
How to prepare
- Decide the purpose. Write one sentence about why you’re fasting. It helps you stay focused when hunger shows up.
- Set the length in advance. If you’re new to fasting, start small, such as skipping one meal or ending your eating earlier in the evening. Keep any fast short until you know how your body responds.
- Choose a sensible day. Avoid days with hard physical work, long drives, intense exercise or major deadlines.
- Eat well beforehand. A balanced meal with protein, whole grains, vegetables and some healthy fat helps you start steady. Skip the “last big feast” approach, which often leads to an uncomfortable fast.
- Hydrate the day before. Drink regularly in the hours leading up to the fast.
- Tell someone. Let a family member know, especially if you live alone or have a health condition.
During the fast
- Fluids: Unless your practice says otherwise, drink water throughout. Some traditions fast from both food and drink. If that’s your practice, keep it short, avoid heat and heavy exertion, and talk with a healthcare provider first if you have any medical condition.
- Activity: Light movement such as an easy walk is fine for most people. Save harder workouts for eating days.
- Hunger waves: Hunger tends to rise and fall rather than build steadily. A glass of water, a short walk, or turning your attention back to the purpose of the fast often helps a wave pass.
- Use the time: Spend the time you’d normally spend on meals in prayer, reading, writing in a journal or reaching out to someone who needs help.
Stop the fast early if you notice
- Dizziness, light-headedness or fainting
- Shakiness, confusion or a racing heart
- Severe headache, nausea or vomiting
- Very dark urine or little urine
Ending a fast early for your health is wise, not a failure.
How to break a fast
Breaking a fast gently helps your stomach and makes it less likely you’ll overeat.
- Start with water or a glass of milk, then a small, easy meal: soup, eggs on toast, yogurt with fruit, or a bowl of oatmeal.
- Wait 20 to 30 minutes before deciding whether you need more.
- Eat slowly and sit down to eat. Notice the taste and the feeling of being fed.
- Go back to your normal, balanced eating at the next meal rather than “making up” for the fast.
Other ways to fast
Fasting doesn’t have to mean food. If food fasting isn’t safe or wise for you, these can carry the same spirit of discipline and focus:
- A day or week without social media, streaming or news
- Skipping a habitual treat, such as sweets or snacking after dinner
- Giving up a convenience, like driving short distances, and walking instead
- Silence for part of the day, replacing noise with reflection
- Giving the time or money you’d usually spend on something to someone in need
A simple fasting plan for beginners
| Step | What to do |
|---|---|
| The day before | Write your purpose. Eat balanced meals. Drink water regularly. |
| Start | Finish a normal dinner. Begin the fast after it. |
| During | Water (unless your practice differs). Light activity. Use meal times for reflection. |
| End | Water or milk, then a small, easy meal. Eat slowly. |
| After | Return to normal meals. Jot down how you felt and what you’d change next time. |
When to check with a professional
Talk with your doctor or pharmacist before fasting if you take any regular medication, have diabetes, heart, kidney or liver disease, are pregnant or breastfeeding, or are over 65. If you have a history of disordered eating, talk with your healthcare provider and consider a non-food fast instead. If fasting leaves you feeling unwell or preoccupied with food, stop and get support.
For a gentler way to work with meal timing, see our guide to circadian meal timing.
Key takeaways
- Know your purpose: spiritual focus and weight management are different goals.
- Evidence that fasting beats ordinary healthy eating for weight loss is limited.
- Skip food fasting if you have diabetes, an eating disorder history, are pregnant or breastfeeding, or are still growing, unless your doctor says otherwise.
- Start short, avoid demanding days, and stop if you feel unwell.
- Break the fast slowly and return to normal meals.
- Non-food fasts are a valid option.