Intermitent fasting: how to do it?

Intermittent Fasting: Why, who, how and when?

One of the latest "trendy diets" is intermittent fasting. Not the one done for religious reasons, but to adopt it as a habit and healthy lifestyle, whether with the goal of losing weight, gaining muscle mass, or just for the sake of detoxifying the body.

What is intermittent fasting?

It consists in adopting a new eating schedule on certain days of the week by cutting down the number of hours you can eat. It has been proven that it is easier for human beings to diet two or three times a week than to stick to it 7 days a week.


How you should do it.

2 methods are recommended:
1) The 16/8 method: you restrict the daily eating period to 8 hours. After this 8 hour period you fast for the next 16 hours. Skipping breakfast and eating only between 1 and 9 p.m. is a popular way of doing it. Another way of doing it is to eat until 3pm and fast until breakfast. Try both and see what suits you the most.
2) Eat-Stop-Eat: involves don't eat for 24 hours, once or twice a week. For instance, you eat on Monday, fast on Tuesday, returning to eat only on Wednesday.


What it does to your body.

The whole idea of this diet is to allow insulin levels to drop low enough to burn our fat.
The food we eat is broken down by enzymes in our intestines and ends up as the molecules in our bloodstream.
Carbohydrates are quickly broken down into sugar, which our cells use for energy. If our cells don't use all of it, they store it in our fat cells. But sugar can only enter our cells to insulin, a hormone produced in the pancreas. Insulin brings sugar into the fat cells and stores it there.
Between meals, if we don't snack, our insulin levels drop and our fat cells release the stored sugar, to be used as energy. We lose weight if we let our insulin levels go down. 

Will this regimen help you lose weight?

There are only two ways to lose weight:
1) reducing the calories you eat and/or
2) consuming more energy, for example through physical exercise.
Eating fewer meals can lead to caloric intake reduction, allowing the body to burn accumulated fat. Furthermore, during this process hormone levels are altered to facilitate weight loss and gain muscle mass. Obviously it is not a cure-all. It depends on the person's own metabolism and body.
Some studies suggest that people tend to eat more before the abstain period, because they know they will not be able to eat during several hours. If you eat the same number of calories and do the same kind of training, don't expect to lose weight.

Is intermittent fasting healthy or not?

Many studies suggest that it is, but only the short term effects have been observed, because it is a recent practice. 
A growing body of research indicates:
- it can help lose weight
- lower blood pressure and cholesterol
- slow the progression of Parkinson’s and Alzheimer’s diseases, as in this diet, the metabolism leads to the production of ketone bodies which have been linked to improved thinking, learning and memory.
- reduce cancer risk because decreased blood glucose production and intake and increased production of tumor-killing cells

Isabel do Carmo, a famous endocrinologist with a vast experience and knowledge in the food area wrote a great new book in which she analyzes several trendy diets and shows her view about intermittent fasting. You can discover a little bit more about the book Food Myths and Facts, a scientific perspective here.


Everybody can do it?

It is not recommended for children, people who tend to have low blood pressure, diabetics or people with a deficit of sodium, potassium and other minerals. Skipping meals and severely limiting calorie intake can be dangerous, so you should always consult your doctor before starting any dietary restriction, even if you are a healthy person.

Does It works if performed with the keto diet?

The Keto diet is low in carbohydrates which, as we mentioned above, supply energy to the cells. It is based on the same metabolic process as the above diet, which kicks in when the body runs out of glucose and starts burning stored fat.
Some nutrition experts worry that the keto diet, which usually includes large amounts of meat, eggs, and fat, can bring quite a few cardiovascular risks.
Intermittent fast is probably a healthier option, especially if you eat a balanced diet that includes whole grains, nuts, legumes, fruits, and vegetables, rich in nutrients known to reduce the risk of heart disease.
Periodic fast triggers the same process that occurs during a low-carb or keto diet and turns out to be more beneficial. 


Photo @sararahmani


Gunnars, K. (April 20,2020), Intermittent Fasting 101 — The Ultimate Beginner’s Guide. Healthline. Consulted in 28/04/2021. 

Cabo, R. and Mattson, M. (December 26, 2019), Effects of Intermittent Fasting on Health, Aging, and Disease. The new England journal of medicine. Consulted in 27/04/2021

Tello, M. (JUNE 29, 2018, update February 10, 2020). Intermittent fasting: Surprising update.Harvard Health Publishing. Consulted in 27/04/2021

De Cabo, R. and Mattson MP. (2019). Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine. Consulted in 28/04/2021


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