Intermittent Fasting

Dr Thanh-Tam Pham - 7/3/2021


In prehistoric times before humans knew farming, they were hunters and gatherers and they could go without eating for long periods of time. It took a lot of energy and time to hunt game or gather fruits and nuts. Nowadays, with the advance of electronic devices, people spend more time sitting watching televisions, using computers and playing games so the lifestyle has changed significantly with less activity and with eating snacks between meals, there is a higher risk of obesity, type 2 diabetes, heart disease and other degenerative diseases.

John Hopkins neuroscientist Mark Mattson,phD, has studies intermittent fasting for over 25 years.

What is intermittent fasting?

There are several different ways to do intermittent fasting but they are all based on choosing regular time periods to eat and fast. One of them is eating only over an 8 hour period each day and fasting for 16 hours or another one when people choose to eat only one meal a day 2 days a week and eat 3 meals the other 5 days.

After several hours without food, the body uses up its sugar stores and starts to burn fat for energy. If one is eating 3 meals a day plus snacks and not exercising, the body uses the calories from the 3 meals and not burns the fat store or even accumulating more fat if eating in excess. It can take 2 to 4 weeks for the body to be accustomed to the intermittent fasting and you might feel hungry and cranky. Mattson observed that subjects who make it through the adjustment period tend to stick with the plan because they notice they feel better. Fat burning begins approximately after 12 hours of fasting and increases between 16 and 24 hours of fasting.

Benefits of intermittent fasting

Mattson’s studies published in the New England Journal of Medicine reveal a range of benefits of intermittent fasting. Intermittent fasting can protect organs against chronic diseases like type 2 diabetes, heart disease, age related neurodegenerative disorders and even inflammatory bowel disease and many cancers.

According to Mattson, during fasting period, cells are under a mild stress and they respond adaptively by enhancing their ability to cope with stress and may be to resist diseases. There is a similarity between how the cells respond to the stress of exercise and how cells respond to intermittent fasting. Vigorous exercise stresses the muscles and the cardiovascular system but as long as the body has time to recover, it will grow stronger.

1-   Intermittent fasting and weight loss:

With intermittent fasting, you eat fewer meals and unless you compensate by eating much more in other meals, you will end up taking fewer calories. Fasting lowers insulin levels and increases growth hormones and noradrenaline which increase breakdown of body fat and facilitates its use for energy. Short term fasting actually increases the metabolic rate together with the reduction in food consumption can cause weight loss and loss of belly fat. In one study in overweight adults with moderate asthma, participants lost 8% of their initial body weight over 8 weeks. They also saw a decrease in markers of oxidative stress and inflammation and improvement in asthma related symptoms.

2-   Reduce oxidative stress and inflammation in the body:

Oxidative stress involves free radicals (unstable molecules) which react with other important molecules like protein and DNA and damage them. Oxidative stress leads to ageing and development of many chronic diseases. There is evidence that a persistent high fat diet affects mitochondrial function and lipid metabolism in skeletal muscles leading to premature tissue ageing. Intermittent fasting was shown to be effective in limiting mitochondrial damage and metabolic disturbances induced by high fat diet.

3-   Reduce insulin resistance and lower the risk of type 2 diabetes, obesity and prevention of cardiovascular disease.


4-   Improve brain health:

Mattson also researched the protective benefits of fasting to neurons. If you do not eat for 10-16 hours, the body uses its fat store for energy and ketones will be released into the bloodstream. This has been shown to protect memory and learning function as well slows the disease processes in the brain. Intermittent fasting may increase the growth of new nerve cells (neurogenesis) in rats. It also increases levels of brain hormone called brain derived neurotrophic factor (BDNF), a deficiency of which has been implicated in depression and various other brain problems. Animal studies have shown that intermittent fasting protects against brain damage due to stroke. Other studies in animals have shown that intermittent fasting may help to prevent Alhzeimer’s disease and other neurodegenerative disease like Parkinsons’s and Huntington’s diseases.

5-   Intermittent fasting induces various cellular repair processes.

During fasting the body initiates a cellular “waste removal” process called autophagy. This involves removal of the dysfunctional cells and recycles parts of them towards cellular repair and cleaning. In intermittent fasting and ketogenic diet, blood glucose level is low and insulin is low with high glucagon levels. Glucagon is the one that initiates autophagy. According to Dr Luiza Petre, autophagy is beneficial in removing toxic proteins from the cells of neurodegenerative diseases such as Parkinson’s and Alhzeimer’s diseases. Autophagy declines with age and fasting increases autophagy and thus may play a role in preventing cancer by recognizing and destroying abnormal cells and trigger the repairing process.

6-   Intermittent fasting may have anti-ageing effects and prolong lifespan in rats.

Caloric restriction, undernutrition without malnutrition is the only experimental approach that was consistently shown to prolong survival in animal models. But intermittent fasting with compensatory overeating did not improve mouse survival nor did it delay prostate tumour growth.

To improve health, the goal should be to lose weight by reducing the total amount of calories consumed rather than only focussing on when those calories are consumed.

Overeating and binge eating are 2 common side-effects of intermittent fasting.

Intermittent fasting is not suitable for everyone especially in children, pregnant women, diabetes patients on medication and some people with chronic diseases.