Should women really fast?

Ask Dr. Jason Fung

There are tons of questions about intermittent fasting, like these

  • Should I take supplements when fasting?
  • Can fasting have a negative effect on women?

Dr. Jason Fung is one of the world’s leading experts on fasting for weight loss or diabetes reversal. Here are a his answers to those questions and more:

Women and Fasting

I have heard that fasting can have negative side effects for women. Can you tell us more about that? Should women be concerned?


There is no more problems with women and fasting than with men and fasting. Please refer to my blog post about women and fasting for details.

Dr. Jason Fung

Supplements for fasting

Dr. Fung, very useful info.
Ramadan is right around the corner and I’ll be working very long hours at a bank. I want to take some supplements before sunrise to make sure my body’s getting the right nutrients, and my mind is prepared for daunting brain-draining tasks. Anything you would recommend? Thanks!!!

A general once a day multivitamin is sufficient. The body is able to supply all the brain’s requirements for energy during fasting. Most people feel their brain function increase, not decrease during fasting.

Dr. Jason Fung

The connection between calorie restriction and fasting

Hi Dr. Fung,
Where is the line between calorie restriction and fasting? At the moment, I’m mostly doing 16:8, ie, skipping breakfast, having my main meal at lunch and having a light supper such as broth with maybe some butter and an egg or some fried bacon. It occurs to me that this might be slipping into calorie restriction and my body could start burning less energy (as described in you analogy with coal power station).
I ask partly because of a surprise increase in weight over the last three days. Although this could be a blip.

It has nothing to do with calories. It has to do with reducing insulin to allow fat stores to be used for energy. There’s no easy answer to this question.

Dr. Jason Fung



Intermittent Fasting for Beginners

More questions and answers

Many more questions and answers:

Intermittent Fasting Q&A

Read Dr. Jason Fung’s new great book The Obesity Code for many more insights:

The Obesity Code

Videos about intermittent fasting

What is Fasting? – Dr. Jason Fung
How to Maximize Fat Burning – Dr. Jason Fung
How to Fast – The Different Options – Dr. Jason Fung
The 7 Benefits of Fasting – Dr. Jason Fung
The Top 5 Myths of Fasting – Dr. Jason Fung
Breakfast! Is It Really That Important? – Dr. Jason Fung
The Most Common Questions – Dr. Jason Fung
5 Tips to Make Fasting Easier – Dr. Jason Fung
How to Get Started with Fasting – Dr. Jason Fung
The Power of a 7-Day Fast – Dr. Jason Fung
Who Is Dr. Jason Fung?
The Perfect Treatment for Weight Loss and Diabetes – Dr. Jason Fung
The 2 big lies of type 2 diabetes – Dr. Jason Fung
The Key to Obesity – Dr. Jason Fung
How to Reverse Diabetes Type 2 – Dr. Jason Fung
The Etiology of Obesity – Dr. Jason Fung


  1. wendy
    40 year old female - enjoy 24 hour fasts twice a week and do 18:6 every week day. Love the info here!! Thank you :)
  2. Apicius
    Interesting read tonight, I came across a very old Italian cookbook, written before 1900, where the author, Pellegrino Artusi, gives some eating advice...which included, when you wake up and don't feel hungry it's ok just to have coffee, and perfectly normal just to drink coffee and that's it. He also states that complete digestion takes seven hours or more, which is why it is recommended to eat supper late at night (in fact I notice how Europeans eating much later at night than Americans do). He also stresses respecting not eating within the minimum seven hours window to not disturb digestion. Since supper is eaten so late at night, then the breakfast is skipped, with only coffee, since it is so close to the end of the digestion period, and perfectly normal not to break the fast. How bizarre...we lost these old customs of eating. Wise recommendations of our ancestors. I'm so angry that my Europen heritage has been spoiled by the BS recommendation of American "expert nutritionists". Too bad, I don't live by the traditions of my roots.

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