What is it?

Intermittent fasting (IF) is an eating pattern that alternates between periods of eating and fasting. It does not prescribe specific foods to eat but focuses on when you should eat them. Common methods include the 16/8 method (fasting for 16 hours and eating during an 8-hour window), the 5:2 diet (eating normally for five days and reducing calorie intake for two days), and the 24-hour fast (fasting for a full 24 hours once or twice a week).

How does it work for medicinal purposes?

Intermittent fasting works by allowing the body to enter a fasting state, which triggers various metabolic processes. These include ketosis (burning fat for energy), autophagy (cellular repair and recycling), and improved insulin sensitivity. These processes help reduce inflammation, support weight loss, enhance brain function, and promote overall health and longevity.

What are the active mechanisms that are important for its medicinal properties?

• Ketosis: Burns fat for energy when glucose levels are low.
• Autophagy: Cleans out damaged cells and regenerates new ones.
• Hormonal Regulation: Increases insulin sensitivity and reduces levels of insulin and cortisol.
• Gene Expression: Promotes longevity genes and reduces disease risk factors.

What forms does it come in?

• 16/8 Method: Fasting for 16 hours and eating during an 8-hour window.
• 5:2 Diet: Eating normally for five days and reducing calorie intake for two non-consecutive days.
• 24-Hour Fast: Fasting for a full 24 hours once or twice a week.
• Alternate-Day Fasting: Alternating between days of normal eating and fasting.
• Eat-Stop-Eat: Fasting for 24 hours once or twice a week.

What if I have an imbalance or deficiency?

Intermittent fasting can help address metabolic imbalances, improve insulin sensitivity, and reduce inflammation. However, it is essential to ensure adequate nutrient intake during eating periods to avoid deficiencies. Consulting with a healthcare provider is recommended, especially for individuals with existing health conditions.

When was it first used for medicinal purposes?

Fasting has been practiced for thousands of years for religious, cultural, and health reasons. Modern intermittent fasting gained popularity in the early 21st century as scientific research began to uncover its health benefits.

What does Intermittent Fasting help with?

Intermittent fasting means you eat within set hours. For the rest of the day, you take a break from food. People in many cultures have fasted for a very long time.

The human research is strongest for blood sugar, weight and blood pressure. Much of the brain and aging work comes from animals or lab dishes. Each use below gets its own grade.

• Insulin resistance and prediabetes
  Good evidence — clinical trials in people with insulin resistance; no single trial named in our file. In people with insulin resistance or prediabetes, weeks of regular fasting lowered fasting blood sugar and insulin. Researchers treat this as one of the best-supported uses of fasting. Our file does not name the single studies or their sizes.
  Evidence grade B · Traditional tier T0
• Losing weight and body fat
  Good evidence — human trials running 8 to 12 weeks. In human trials, people who fasted lost body weight and body fat. Most of that loss showed up within 8 to 12 weeks, without close calorie counting. Insulin is well established as the hormone that signals fat storage, and it falls while you fast.
  Evidence grade B · Traditional tier T0
• Managing type 2 diabetes
  Good evidence — several clinical trials in people with type 2 diabetes. Several clinical trials found lower HbA1c, a long-term blood sugar marker, and lower fasting glucose. The results were about the same as daily calorie cutting. Some people in trials took less diabetes medicine, but only under a doctor's care.
  Evidence grade B · Traditional tier T0
• High blood pressure
  Good evidence — trials of time-restricted eating that measured blood pressure. Studies of time-restricted eating found lower top and bottom blood pressure numbers. The drop showed up even when people did not lose weight. It looked largest when meals were packed into the earlier part of the day.
  Evidence grade B · Traditional tier T0
• High cholesterol and triglycerides
  Early evidence — human studies of blood fats; no trial size or dose on file. In people with high blood fats, fasting lowered triglycerides and LDL cholesterol. HDL, the so-called good type, often went up. Researchers explain this by less carbohydrate during the fasting window, which cuts the liver's output of VLDL particles.
  Evidence grade C · Traditional tier T0
• Metabolic syndrome
  Early evidence — human studies of the separate markers, none named in our file. Metabolic syndrome means five problems at once. They are high blood sugar, belly fat, high triglycerides, low HDL and high blood pressure. Studies found fasting moved all five markers in a better direction, though no single trial is named here.
  Evidence grade C · Traditional tier T0
• Long-term inflammation and aging markers
  Early evidence — human studies of blood markers; the longevity data is observational only. In human studies, fasting lowered inflammation markers such as CRP and IL-6. These markers are tied to heart disease, diabetes and autoimmune illness. In lab and animal work, fasting switched on autophagy, the cell's clean-up of damaged parts.
  Evidence grade C · Traditional tier T0
• Sharper thinking and brain health
  Not yet tested in people — strong animal research; human trials still early and not detailed in our file. In animal research, fasting raised BDNF, a protein tied to memory, learning and brain cell survival. While you fast, the body makes ketones, which the brain can burn; that is basic physiology, not a trial of focus. Human trials are still early, so no claim about mental clarity can be made.
  Evidence grade insufficient · Traditional tier T0
• Bloating, SIBO and gut comfort
  Not yet tested in people — no human trial on file; mechanism reasoning only. The migrating motor complex is a known cleansing wave in the small intestine that runs between meals. The idea is that longer gaps without food give it more time to work. Our file holds no human study testing this for bloating, SIBO or gut repair.
  Evidence grade insufficient · Traditional tier T0

What Intermittent Fasting has not been shown to do

• No human trial on file shows that fasting makes people live longer; that evidence is animal work and observation.
• Fasting has not been shown in human trials to sharpen focus, memory or mental clarity.
• It has not been shown to cure type 2 diabetes or to replace blood sugar medicine.
• No human study on file shows it eases bloating or lowers SIBO risk.
• It has not been shown to beat daily calorie cutting; in diabetes trials the results were about the same.

How to read this:

A means several good human trials agree. B means at least one good human trial. C means small or early human work. D means the human evidence is weak or mixed. Insufficient means no human study on file. This page reports what studies found. It is not medical advice, and it is not a promise of results. If you take medicine for blood sugar or blood pressure, talk to your doctor before you fast.

What can Intermittent Fasting help prevent?

• Type 2 diabetes progression (in people with prediabetes)
• Cardiovascular disease risk factor accumulation
• Age-related metabolic decline

Which foods are rich in it?

Intermittent fasting is an eating pattern, not a food source. However, consuming nutrient-dense foods during eating periods is essential for health. Focus on:

1. Vegetables
2. Fruits
3. Lean Proteins
4. Whole Grains
5. Healthy Fats (e.g., avocados, nuts, olive oil)
6. Legumes
7. Dairy or Dairy Alternatives
8. Seeds
9. Fish
10. Poultry

What are possible side effects?

Intermittent fasting is generally safe for most healthy individuals, but possible side effects include:

• Common (10-30%)
• Hunger
• Fatigue
• Irritability
• Less Common (1-10%)
• Headaches
• Dizziness
• Digestive issues (e.g., constipation, bloating)
• Rare (<1%)
• Nutrient deficiencies (if not eating a balanced diet)
• Disordered eating patterns

What’s the recommended daily dose?

There is no specific "dose" for intermittent fasting. The method and duration of fasting depend on individual preferences and health goals. Common patterns include:

• 16/8 Method: Fast for 16 hours and eat during an 8-hour window daily.
• 5:2 Diet: Eat normally for five days and reduce calorie intake (500-600 calories) for two non-consecutive days.
• 24-Hour Fast: Fast for 24 hours once or twice a week.

How many days does it take to work?

Some benefits of intermittent fasting, such as improved mental clarity and reduced hunger, can be noticeable within a few days. Long-term benefits, such as weight loss and improved metabolic health, may take several weeks to months to become apparent.

What time of day is best to do it?

The timing of intermittent fasting depends on the chosen method. For the 16/8 method, common eating windows are from noon to 8 PM or from 10 AM to 6 PM. It is essential to choose a fasting schedule that fits your lifestyle and preferences.

Is it best to do it with or without food?

Intermittent fasting involves periods without food intake. During eating windows, it is crucial to consume nutrient-dense foods to meet your nutritional needs. Drinking plenty of water and non-caloric beverages (e.g., herbal tea, black coffee) during fasting periods is also important to stay hydrated.