Does intermittent fasting work?

Whether you’re applying it to your own life or simply want to read more about it, we’ve sourced the expert insight of nutritionist, Marli Havinga, to fill you in on everything you need to know about the world’s hottest weight-loss trend.

What is intermittent fasting?

Intermittent fasting is an eating pattern, unrelated to religious or cultural customs, where you allocate a recurring interval for fasting (no caloric intake) and eating.

The trend is especially popular since it affords people the opportunity to continue eating whatever they choose, and simply to reduce the window period for consuming calories, whereas other diets like caloric deficit require you to track every calorie you consume.

There are several variations of intermittent fasting, but the most common routine is to eat within 8 hours of a 24-hour day. Here are some of the most popular fasting periods applied by the Zero Fasting community:

Fasting hours  


13 hours Fast from sunrise to sunset or according to circadian rhythm
16 hours Eat within 8 hours, fast for 16 hours
18 hours Eat within 6 hours, fast for 18 hours
20 hours Eat within 4 hours, fast for 20 hours


It’s important to note that 8 hours of your fasting period will be reduced by sleep, provided that you follow a consistent sleep routine. 

What are the benefits of intermittent fasting?

The major benefits of intermittent fasting include weight loss and improvement to insulin sensitivity. It also has anti-inflammatory effects, promotes cell regeneration, improves gut health, and has been found to reduce the risk for cardiovascular disease. A study on the benefits of intermittent fasting for weight loss determined that caloric restriction and intermittent fasting result in similar degrees of weight loss and improvement to insulin sensitivity.

When is the best time to fast?

The best time to fast is in the morning since this prolongs the period of fasting while sleeping, unless you’re accustomed to late-night snacking. Your liver and muscles store glucose for when your body needs it and once the glucose reserve has been used, your body will create its own glucose using mainly fat. This is why most people fast in the morning and start to eat from about 4 – 6 hours after waking up.

Can you exercise while fasting?

Havinga advises against exercise during a full day of fasting since the body needs energy for any type of exercise or sport. “The body’s stores can only keep up for so long and then it must be refueled. In cases where time-restricted fasting is practiced, an individual can exercise or participate in sport but not an endurance sport.”

What can you drink while fasting?

You can drink any fluids containing no calories. Start drinking water immediately when you wake up and continue hydrating your body until you can eat. You can also have unsweetened black coffee, tea without dairy, sparkling or still water, soda water, Zero cold drinks and Light cold drinks.

What should you eat after fasting periods?

Start with a small, nutritious meal because a large meal can lead to abdominal discomfort and impact insulin response. Stick to healthy eating habits and consume a variety of foods to maintain macronutrients in your diet.

Are there any side effects?

Always consult a healthcare professional before starting any diet. Irresponsible fasting or fasting with a pre-existing health condition can lead to hypotension and hypoglycaemic episodes.

Since fasting increases uric acid levels in the body, this could also lead to episodes of gout and gallstones.

Havinga also notes that once your body has adapted to fasting, the metabolism can slow down to such an extent that the loss of fat eventually slows to less than would be achieved with a low caloric diet.


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