29 February 2020
We should keep a balanced diet because the human body always requires energy to function. Photo: Bloomberg
We should keep a balanced diet because the human body always requires energy to function. Photo: Bloomberg

The myth of intermittent fasting

More and more people detox and try to lose weight by fasting.

Some only consume liquid like veggie drinks or water for a few days, some fast every other day, and some stop eating once they reach 70 percent full. The principle behind all of these variations is to reduce calorie intake either gradually or intermittently.

The 5:2 diet is currently the most widely adopted form of intermittent fasting diet founded in Britain. As its name implies, the diet consists of five days of normal eating and two days of restricted diet.

Not only could it help balance out the calorie intake of the whole week, it could also curb cravings and allow participants to get used to choosing low-calorie food options in those two days and make wiser choices later on.

Fasting diets are rumored to help in losing weight and nourish mind and body, but do such beliefs have medical support?

The calories in food are like banknotes in our wallet. We spend every day and if we do not have an income, we need to mobilize our savings. When people stop eating, their body would convert glycogen stored in the liver into glucose, and later burn fats, for energy supply.

However, ketonic acid, a metabolite produced during the process, may accumulate and cause ketoacidosis or metabolic arthritis due to the spike in uric acid levels.

Jamie, a follower of this fasting trend, stopped eating for 10 days and took only tree syrup and water. She lost 10 pounds as a result. The percentage of fat in her body dropped to 24 percent from 27 percent. But she felt feeble and weak.

The president of the Hong Kong Association for the Study of Obesity, Dr. Francis Chow Chun-chung, had misgivings about Jamie’s rapid weight loss. He reminded the public not to glorify intermittent fasting despite the numerous seemingly supportive clinic studies.

Professor Justin Wu Che-yuen, director of The S.H. Ho Centre for Digestive Health from The Chinese University of Hong Kong, also stressed that it could be life-threatening not to drink for three days and not eating for seven days could deplete all energy stored in the body.

As a nephrologist, I would suggest keeping a balanced diet at all times because the brain and the kidneys always require energy to function. Whether we adopt a low-calorie diet or a caloric one, it should include grains, protein from dairy products and meats, vegetables and fats.

A nutritious meal is a prerequisite for managing our overwhelming workload.

This article appeared in the Hong Kong Economic Journal on Dec 18

Translation by John Chui

[Chinese version 中文版]


Chair of Renal Medicine and Yu Professor in Nephrology, Li Ka Shing Faculty of Medicine of the University of Hong Kong