• Virina Chan

More about intermittent fasting

Virina Chan, HK BioTek Intern




Intermittent fasting has been popular for weight reduction and health-boosting. This is because such a method is viewed as no tough restrictions on food choice. Fasting, unlike starvation, is a voluntary and temporary action that longs from several hours to days. It is a regular dietary pattern that people eat and fast at a consistent period with appropriate caloric intake. Initially, this is a common religious etiquette in many religions for many centuries. Recently, health professionals consider such short-term food inhibition as a beneficial practice.

How does it work?

Normally, the food we eat will be digested and either be used by the body or stored. Carbohydrates and fats are the primary energy sources for body cells. After a meal, these nutrients are broken down rapidly for energy. At the same time, insulin, a hormone, will convert glucose to glycogen to store energy in the liver and muscles. When the storage is full, the excess nutrients will stay in our body as fats. Thus, the more we eat, the more fats are stored in the body. Therefore, excessive eating, in the long term, will lead to obesity and other diseases. This is when fasting can be applied to reverse this situation. During fasting, glycogen and fats from body cells are the only fuels used for energy such that glycogen will first be broken down and fats after glycogen being used up to maintain body functioning. This reaction occurs within 8 to 12 hours after the start of fasting and reaches an optimum speed in 24 hours. This is why the typical duration of intermittent fasting ranges from 16 hours to one day. Thus, as we reduce the overall calorie intake, less fat can be stored in the body, preventing weight gain.

Types of intermittent fasting

The duration of fasting varies from several hours in one day to 2 days per week. There is no best method to follow. However, some widely discussed options attract more population to follow:

  1. Daily time-restricted feeding (16:8 diet / 20:4 diet)

This is to eat and fast in a certain period. In one day, you have to divide two timeslots for eating and fasting, respectively. There are two ways: 16:8 and 20:4 diet. People who do 16:8 fasting have to finish all their meals within an 8-hour time, then fast for the upcoming 16 hours. For a 20:4 diet, only a 4-hour time is allowed for a meal, and the remaining 20 hours will be fasting. It is recommended to work on an 18:8 diet before 20:4 diet due to longer fasting hours.

  1. 5:2 fasting

Compared to other fasting regimens, the 5:2 fasting is most scientifically supported. This works on a weekly basis. Within a week, there are two non-consecutive days of fasting and five days of regular feeding. Despite the name “fasting”, individuals reduce their caloric intake to not more than 500 kcal. This roughly equals one meal. Of course, you can consume food at any time as long as you meet the caloric requirement.

  1. Alternate-day fasting

This has a similar approach to 5:2 fasting. Rather than two days per week, participants need to fast for every two days. In other words, you fast on day 1 and normally eat on day 2 and fast again on day 3—the cycle repeats.

There are other kinds to refrain from eating. Some even extend the period of voluntary fast to more than 48 hours. However, it requires supervision from health professionals.

What can be gained from it?

The major benefit is weight loss. Studies found that intermittent fasting and bring 3-8% weight reduction in 3-24 weeks. Other than weight loss, there are many more health benefits than you can imagine.

There are some potential benefits, along with weight loss:

Physical and aesthetic outcome

  • Better running endurance

  • Balance and coordination

  • Loss in body fat

  • Better lean to fat ratio (can maintain muscle mass)

Chronic diseases

Management and prevention of:

  • Overweight and Obesity

  • Dyslipidemia

  • Hypertension

  • Inflammation

  • Lower insulin resistance

  • Lower cancer risk

  • Longer lifespan

  • Delay Alzheimer’s and Parkinson’s diseases

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