Fasting, Weight Loss and Obesity

Fasting, weight loss and Obesity

We have known about fasting for ages. It is usually related to religious practices, however, more and more of us choose to fast for health-related reasons. Multiple studies have suggested that intermittent fasting may have many health benefits.


What is fasting?

Fasting is different from dieting. It is not about the type of food that we eat or calorie restriction but rather about the time frame within which we consume our daily food. Fasting refers to abstaining from food for a given amount of time. Some suggest that among people who consume the same calorific value from their meals, those who fast are more likely to have lower blood pressure, higher insulin sensitivity, more appetite control, and easier weight loss.

There are many types of fasting diets that differ from each other in terms of the fasting period and amount of food allowed within the ‘eating window’.

  • Meal skipping –skipping a meal of our choice depending on the level of hunger, rather than following strict meal times without paying attention to our hunger signals.
  • 5:2 diet – a diet where we eat a recommended amount of calories for 5 days a week and reduce our calorie intake to 500kcal for women and 600kcal for men for the remaining 2 days of the week.
  • Alternate-day fasting – involves abstaining from eating for 24 hours, followed by one or more “feast” days when we can eat as much as we want.
  • Eat-Stop-Eat diet – involves fasting completely for 24 hours at a time for 1 or 2 days a week
  • The 16:8 plan – within the 8-hour window we can eat our meals and snacks at convenient times.
  • The Warrior Diet – involves eating very little for 20 hours each day and consuming all the recommended amount of food within a chosen 4 hours period

Benefits of fasting

Studies suggest that there are many benefits related to fasting. These may include reduced cholesterol, lower blood pressure, improved insulin sensitivity, weight loss and increased longevity. Some believe that fasting can help cleanse our body and aid healing processed. They also claim that longer periods of fasting (2-4 days) may be effective for the regeneration of our immune cells. Fasting can also help prevent several conditions. These include type 2 diabetes, heart conditions, some types of cancer or neurodegenerative diseases. However, we need more research to confirm such claims.


Fasting and weight loss

Eating during a set period of the day can help reduce the number of calories we consume. It may also help boost our metabolism. Additionally, during the fasting periods, our body’s ability to obtain energy from food is limited. Therefore, it utilises glucose stored in the liver and muscles, which occurs around 8 hours after we eat the last meal. When these stores have been used up, the body begins to burn fat as a source of energy. Conversely, there may be a risk that during the fasting periods our metabolism slows down. As a result, when we are back to normal eating our body tries to store additional energy.

Many researchers believe that we should not perceive fasting diets as weight loss diets. This is because calorie restriction is very temporary and promotes fast fluid loss but no significant loss of ‘dry weight’. The weight that we manage to lose over the period of fasting gets quickly restored when we re-introduce normal eating. There is also a risk that limiting one’s calories on certain days may then lead to ‘compensating’ on other days, and overeating. However, some people claim that intermittent fasting is easier to maintain long term as it allows more flexibility than common calorie-restricted diets. This flexibility though can also be viewed negatively. Allowing us to eat freely what we want on the non-fasting days may mean that our dietary choices are poor as there is no restriction element involved.



Fasting can be challenging. It can cause fatigue, headaches, irritability or hunger. Overeating or consuming junk food during the eating window can occur due to excessive hunger. Also, when eating a normal diet we provide water not only with drinks that we have throughout the day but also with all the food we consume. When we fast, a large proportion of that water is omitted, which can sometimes lead to dehydration. Some also believe that fasting may trigger eating disorders. Long term calorie restriction could also potentially increase depression.



  1. See your doctor to check if there are any contraindications for you to commence such diet. There are many conditions that we should consider before commencing a fast. Therefore, it is crucial to speak to your doctor before you make any decision.
  2. Pick a method that seems doable for you. Start slow and choose methods that only limits your eating for a short period of time. Once you feel comfortable with this, you can progress to more advanced and demanding regimens
  3. Plan your diet carefully:
  • Drink plenty of water to replace the fluids that would normally come from your food.
  • Pay attention to calories. Eating on a ‘non-fasting days’ does not mean we should eat an uncontrollable amount of calories or binge on junk food. It is vital to follow a healthy, balanced diet and make the calories count, ensuring they come from good sources.
  • On your fasting days choose food that is low in calories but of high volume such as vegetables and fruits
  • It is easier to fast on a busy day when we have no time to eat or think about food and we have a good level of distractions.
  • Try to relax and avoid stress

We will soon be publishing an article explaining the science of fasting in our next blog


Read more about obesity here:


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