Sign in Subscribe

Intermittent Fasting

Intermittent Fasting

Intermittent fasting has become increasingly popular in recent years, with many people touting its potential health benefits. However, it is important to note that not all types of fasting are the same, and some may require more preparation or be less suitable for frequent repetition.

One type of fasting that has gained attention for its potential health benefits is intermittent fasting. This involves alternating periods of fasting with periods of eating, typically within a 24-hour period. The length of the fasting period can vary, with some people opting for shorter fasts of 12-16 hours and others choosing longer fasts of up to 20 hours per day.

Benefits

Studies on animals have consistently shown that fasting can lead to increased longevity, a striking improvement in their health. While there is not yet conclusive evidence from human studies, it is highly likely that similar effects may occur in humans.

The potential increase in longevity from fasting is likely due to the many short and long-term health benefits associated with this practice, that have been shown in humans:

  1. Improved insulin sensitivity: It has been shown to improve insulin sensitivity, improve glucose metabolisme which can reduce the risk of type 2 diabetes and metabolic syndrome. [1]
  2. Reduced inflammation: It has been shown to reduce inflammation in the body, which may help prevent chronic diseases such as heart disease and cancer. [2]
  3. Improved cognitive function: Intermittent fasting may improve cognitive function and protect against neurodegenerative diseases by increasing the production of brain-derived neurotrophic factor (BDNF). [3]
  4. Increased growth hormone production in the body. Research suggests that intermittent fasting can increase growth hormone levels by up to 5-fold, which may have a number of potential benefits, such as increasing muscle mass, reducing body fat, and improving bone density. [1][6][7] However, recent studies have shown that the downstream genes become less sensitive (more growth hormone will be need to produce same amount of IGF-1).
  5. Weight loss: Intermittent fasting has been shown to promote weight loss by increasing fat burning, especially when combined with overall caloric reduction. [4]
  6. It can create some psychological independance to food, and help having a better hunger management

A major factor underlying many of the benefits associated with fasting appears to be the activation of a metabolic switch that shifts the body's primary source of fuel from glucose to fatty acids and ketones. This process typically occurs between 12 and 36 hours after the cessation of food consumption, depending on factors such as the individual's initial liver glycogen levels and their level of energy expenditure or exercise during the fast.[4]

Methodology

The benefits mentioned are almost all under the assumption that the body changes its source of fuel. Therefore we saw that a minimum of 12hours fasting is required. Multiple ways of fasting are commonly practice:

  • Intermittent fasting (IF): This is probably the most common eating pattern, involving fasting for 12 h or longer.
  • Alternate-day fasting: This eating pattern involves consuming no calories on fasting days and alternating fasting days with a day of unrestricted food intake, or a ‘‘feast’’ day
  • Periodic fasting: This eating pattern involves fasting for 1-2 days per week and consuming food freely for the remaining 5-6 days per week.

The IF is perhaps the most widely practiced form of fasting, owing to its convenience and flexibility. By simply skipping breakfast and starting eating at lunchtime, individuals can easily adopt this approach to fasting. Moreover, it is possible to gradually increase the duration of the fasting period, allowing for a more sustainable transition to longer fasts of 16 hours or more.

It is worth bearing in mind, however, that there are certain factors to consider when undertaking intermittent fasting:

  • The timing of the feeding period during intermittent fasting can be flexible and doesn't have to be set from 8pm to 12am.
  • One can consume as many calories as they want during the feeding period without compromising the benefits of the fast.
  • Changing or shifting the feeding window can disrupt the body's clock genes and diminish some of the benefits of intermittent fasting for at least two days.

Now there are often questions related to exercising, muscle mass and fasting period. If someone wants to perform intense exercise and/or increase their muscle mass while practicing intermittent fasting, there are some important considerations to keep in mind:

  • Making sure the caloric intake is sufficient during the feeding period, especially the protein intake
  • For optimal performance one might need to avoid intense exercise during the fasting period
  • To maximise muscle growth it would be ideal to train within the feeding period or at least making sure the protein intake is shortly after the workout

Interestingly, a study on mice has also shown that restricted feeding has reduced the muscle loss due to aging by 40%.[5] This highlight the longterm benefits even on muscle mass.

Summary

Overall, while intermittent fasting may not be suitable for everyone and should be approached with caution, it offers a promising approach to improving health and wellbeing.

  • Reduced inflammation
  • Improved insulin sensitivity
  • Weight loss
  • Improved cognitive function

Even for the one aiming for muscle gains, it is possible to combine it with intermittent fasting, if the training sessions are done during the fed period. With careful planning and preparation, however, intermittent fasting can be an effective and enjoyable way to promote overall health and wellbeing.

References

  1. Tinsley, G. M.; La Bounty, P. M.; Effects of Intermittent Fasting on Body Composition and Clinical Health Markers in Humans. Nutr Rev 2015 73, 661–674. https://doi.org/10.1093/nutrit/nuv041.
  2. Li, G.; Xie, C.; Lu, S.; Nichols, R. G.; et al.;  Intermittent Fasting Promotes White Adipose Browning and Decreases Obesity by Shaping the Gut Microbiota. Cell Metabolism 2017, 26, 672-685 https://doi.org/10.1016/j.cmet.2017.08.019.
  3. Fontán-Lozano, Á.; Sáez-Cassanelli, J. L.; et al; Caloric Restriction Increases Learning Consolidation and Facilitates Synaptic Plasticity through Mechanisms Dependent on NR2B Subunits of the NMDA Receptor. J. Neurosci. 2007, 27, 10185–10195. https://doi.org/10.1523/JNEUROSCI.2757-07.2007.
  4. Anton, S. D.; Moehl, K.; Donahoo, W. T.; et al; Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting: Flipping the Metabolic Switch. Obesity 2018, 26, 254–268. https://doi.org/10.1002/oby.22065.
  5. van Norren, K.; Rusli, F.; et al; Behavioural Changes Are a Major Contributing Factor in the Reduction of Sarcopenia in Caloric-Restricted Ageing Mice: Reduction of Sarcopenia in Caloric-Restricted Ageing Mice. Journal of Cachexia, Sarcopenia and Muscle 2015, 6, 253–268. https://doi.org/10.1002/jcsm.12024.
  6. Ho, K. Y.; Veldhuis, J. D.; et al; Fasting Enhances Growth Hormone Secretion and Amplifies the Complex Rhythms of Growth Hormone Secretion in Man. J. Clin. Invest. 1988, 81, 968–975. https://doi.org/10.1172/JCI113450.
  7. Ge, X.; Yang, H.; et al; LEAP2 Is an Endogenous Antagonist of the Ghrelin Receptor. Cell Metabolism 2018, 27, 461-469.e6. https://doi.org/10.1016/j.cmet.2017.10.016.