16:8 Intermittent fasting

Fasting for 16 hours a day, leaving an eating window of 8 hours, is called the 16:8 method of Intermittent Fasting (IF). On this fast, people usually finish their evening meal by 8 p.m. and then skip breakfast the next day, not eating again until noon.

During use of the IF diet, there are marked metabolic changes in the body. During fasting, when glucose is exhausted, the body begins to utilize ketones that arise as a result of fatty acid transformations. Fatty acids and ketones become the main source of energy for cells. This transition is called intermittent metabolic switching. While the body is abstaining from food, the concentration of glucose, which is the basic energy substrate, decreases. Glycolysis is inhibited. Glycogen reserves in the liver are consumed and the process of gluconeogenesis is activated, during which fats are consumed. In addition, insulin and IGF-1 (insulin-like growth factor-1) levels are reduced in blood and glucagon levels rise. Such biochemical changes are accompanied by cellular and molecular adaptations of neuronal networks in the brain. The result is an improvement of their functionality and resistance to stress, injuries, and diseases.

Intermittent fasting can reduce levels of pro-inflammatory factors, such as homocysteine, interleukin 6 (IL6), or C reactive protein (CRP) which makes it especially beneficial in reducing risk of inflammatory conditions including cardiovascular disease.

The IF diet positively affects the functioning of the nervous system. By affecting the reduction of free radical formation in the body and stress response systems, it protects neurons from environmental and genetic factors that cause them to age.

IF also has its drawbacks. Periods of fasting of a few hours at the start cause problems. This can negatively impact mood at the beginning of the diet, and cause symptoms such as fatigue or dizziness, because the body needs time to get used to using ketones instead of glucose. Certainly, this is not a good diet for patients with reactive hypoglycemia. Moreover, caloric restriction with the simultaneous use of antidiabetic drugs may lead to severe hypoglycemia.

Importance of food quality in the eating window

It is absolutely essential to ensure that meals in the eating window are packed full of nutrients.  One of the easiest ways of doing this is to include:

  • At least 4 cups of vegetables with at least 2 of those cups being made up of green leafy/cruciferous veg (broccoli, cauliflower, spinach, kale, cabbage, brussel’s sprouts, watercress, rocket, etc)
  • Avocado
  • Extra virgin olive oil
  • Free-range, grass-fed proteins
  • Wholegrains and/or legumes

It can be difficult to achieve fibre needs in an 8 hour window so it may be advisable to take a fibre supplement.

Scheme and concept. Clock face symbolizing the principle of Intermittent fasting. Vector illustration. Infographic