Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating.
It doesn’t specify which foods you should eat but rather when you should eat them.
In this respect, it’s not a diet in the conventional sense but more described as an eating pattern.
Common intermittent fasting methods involve daily 16-hour fasts or fasting for 24 hours, twice per week.
Fasting has been a practice throughout human evolution. Ancient hunter-gatherers didn’t have supermarkets, refrigerators, or food available year-round. Sometimes they couldn’t find anything to eat.
As a result, humans evolved to be able to function without food for extended periods of time.
In fact, fasting from time to time is more natural than always eating 3–4 (or more) meals per day.
Fasting is also often done for religious or spiritual reasons.
Types of Intermittent Fasting
Drink only water, coffee, tea, and other calorie-free beverages. No solid foods or calorie-containing drinks are permitted.
For example, if you finish dinner at 7 p.m. Monday and don’t eat again until 7 p.m. Tuesday, you’ve completed a 24-hour fast. Some people choose to fast from breakfast to breakfast or lunch to lunch. But which time frame works best depends on the individual.
A full 24-hour fast every other day can seem extreme and may be difficult for many people to maintain. It’s usually not recommended for beginners. But, you don’t have to go all in right away. Many intermittent fasting routines start with shorter fasting periods.
Here are 5 of the most popular eating patterns for adding intermittent fasting to your diet:
- Time-restricted eating. Involves fasting every day for 12 hours or longer and eating in the remaining hours. A popular example is the 16/8 method. It features a daily 16-hour fast and an 8-hour eating window wherein you can fit in 2, 3, or more meals.
- The 5:2 diet. The 5:2 diet involves eating as you normally do, five days a week. Restrict your calorie intake to 500–600 on the remaining two days.
- Eat Stop Eat. Eat Stop Eat involves a 24-hour fast once or twice per week.
- Alternate-day fasting. With alternate-day fasting, the goal is to fast every other day.
- The Warrior Diet. The Warrior Diet was among the first popular diets to include a form of intermittent fasting. Eat small amounts of raw fruits and vegetables during the day and eat one large meal at night.
Pros and Cons of Intermittent Fasting
Some studies suggest that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss. That seems reasonable because reducing the number of calories you eat should help you lose weight.
Can intermittent fasting improve your health? Losing weight and being active help lower your risk of obesity-related diseases. Such as diabetes, sleep apnea, and some types of cancer. For these diseases, intermittent fasting seems to be about as beneficial as any other type of diet that reduces calories.
Some research suggests that intermittent fasting may improve conditions associated with inflammation:
- Alzheimer’s disease
- Multiple Sclerosis
Implement intermittent fasting with caution. Side effects may include:
To avoid these side effects, eat nutrient-dense food during the eating windows.
Intermittent fasting is safe for many people, but it’s not for everyone. Skipping meals may not be the best way to manage your weight if you’re pregnant or breastfeeding.
Talk to your doctor if you have kidney stones, gastroesophageal reflux, diabetes, or other medical problems.
What food goes best with IF?
One nonrandomized trial showed improved weight loss, blood sugar, and lipids with as little as 14 hours of daily fasting. With no change in the participants’ baseline diet.
That may not mean people can eat whatever they want during the eating window.
In our experience, people have more success with intermittent fasting when eating low-carb.
There is currently insufficient evidence that pairing one type of diet with IF is superior to another.