Intermittent Fasting: How to Start, Types, 8 Health Benefits & More

Updated in April 2023

Intermittent fasting consists of a planned eating schedule in which solid food is not consumed for 16 to 24 hours. It can be applied every day or just several times per week. Once the fasting hours have terminated, you then return to your normal eating, preferably choosing a diet that is low in sugar and fat. This type of diet can promote natural detox mechanisms in the body, boost immunity, and also help improve mood and mental performance.

The most common strategy for beginners it is to fast for 14 to 16 hours. During this time, fluids like water, black tea or black coffee, can be consumed. 

This eating plan is only recommended for healthy individuals. Before starting, you should seek a consult a doctor, nurse, or registered dietitian to assess whether this diet plan is right for you. Once started, you should follow-up regularly with a health care professional to determine whether your health goals are being met. 

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How to start intermittent fasting

There are different ways of following an intermittent fasting plan. All of them consist of periods of eating with periods of fasting.  

If you've never done fasting before, you are advised to try it only once per week for a maximum of 16 hours. You can also start with a shorter fasting period and increase it gradually. 

Before you start fasting, your last meal should be a low-carb meal. That way you won't feel so hungry during the fast. In the first four hours, the body uses the energy provided by this last meal and after that period, the body starts to metabolize cells that contain glucose, which boosts fat burning.

The 4 main types of intermittent fasting

The main types of intermittent fasting are: 

  • 16-hour fasting - this consists of not eating for 14 to 16 hours, including the sleep period, and then eating during the remaining 8 hours of the day. For example, having dinner at 6 pm and then only start eating again at 10 am the next day;
  • 24-hour fasting - this consists of a whole day and night fast, two to three times a week;
  • 36-hour fasting - this consists of not eating for one and a half days. This type of fasting should only be done under doctor supervision and by those who are already used to fasting;
  • 5:2 diet - this consists of eating normally for 5 days and restricting food intake for 2 days by reducing calorie intake to around 500.

During the "no eating" period, you are allowed to have water and tea or black coffee. It is common to feel very hungry in the first few days as the body gets used to it. If you feel extremely hungry, just eat something light as it is not advisable to feel unwell if you are trying to adopt this habit.

Health benefits of intermittent fasting

The main benefits of intermittent fasting include:

  1. Triglycerides and cholesterol regulation: When food that is low in sugar and fat is eaten before and after fasting, excess fat is more easily eliminated, which helps to regulate cholesterol levels.
  2. Faster metabolism: Contrary to popular belief, fasting does not slow down metabolism. Metabolism only becomes slower when fasting periods are prolonged, over 48 hours. With short and controlled fasting periods, there is an increase in metabolic rate, which helps burn fat easier.
  3. Prevent high blood pressure: Intermittent fasting can decrease LDL (bad cholesterol) levels and increase HDL (good cholesterol levels). This promotes optimal blood circulation and prevents hypertension.
  4. Prevent diabetes Intermittent fasting is associated with reduced sugar intake, which helps to balance glucose and insulin levels to prevent diabetes.  
  5. Aid in weight loss: Fasting for at least 16 hours can reduce insulin levels in the blood, as well as stimulate the body to use fat and sugar reserves. This can directly contribute to weight loss. 
  6. Prevent flaccid skin: Intermittent fasting can stimulate the release of growth hormone, which promotes fat burning and muscle gains that prevent flaccidity.  
  7. Natural detoxing: Blood sugar and cholesterol levels automatically reduce after fasting for at least 16 hours, which helps to balance intestinal flora and detox the body. This can be beneficial for preventing health problems like asthma, arthritis, cancer and fatty liver.  
  8. Decreasing cardiovascular disease: Because this diet prioritizes food that is rich in fiber, vitamins and antioxidants, intermittent fasting can help to prevent the formation of fatty plaques in the blood vessels, which reduces cardiovascular diseases like heart attacks, strokes and atherosclerosis. 
  9. Preventing early aging: Decreasing sugar and fat intake while increase fiber, minerals and vitamins helps to reduce systemic inflammation, promote hydration and stimulate collagen production. This helps to decrease the appearance of wrinkles and overall early aging. 

Additionally, due to hormone regulation, people who fast intermittently may also notice increased mental alertness, sharpness and overall well-being. 

What to eat after fasting 

After a fasting period you should only eat easy-to-digest, low glycemic foods and avoid fatty and sugary foods, in order to achieve better results. 

When you break your fast, it is important to ingest low glycemic foods such as: 

  • Mushrooms;
  • Sweet potato;
  • Zucchini;
  • Quinoa;
  • Chicken breast;
  • Tin tuna or sardines;
  • Broccoli;
  • Spinach;
  • Tomato;
  • Cabbage;
  • Cauliflower;
  • Bone broth.

Eating fruits like apple, strawberries, raspberries, and blueberries is also advised. In addition, the longer you go without eating, the less the amount of food you should have as a first meal. 

Foods to avoid

Avoid deep-fried foods, frozen food or fatty food like french fries, deep-fried chicken, ice cream, cookies, and lasagna. 

In order to lose weight when fasting intermittently, it is also important to exercise regularly. This can include going for a walk or exercising at the gym. However, do not do so on an empty stomach and seek the supervision of an exercise instructor.

Is intermittent fasting for everyone?

Although it has numerous health benefits, intermittent fasting is not recommended for people who have diseases like anemia, high blood pressure, low blood pressure or kidney disease, or those who require prescription medication on a daily basis.

It is also not recommended for:

  • People who have had or have anorexia or bulimia;
  • Diabetics;
  • Pregnant or breastfeeding women.

However, even those who are apparently healthy should have a check-up with a general practitioner to assess their overall health before starting this type of of diet. The doctor may order testing, like blood sugar tests, to ensure you are physically capable of handling long fasting periods.