Intermittent Fasting - PROS and CONS

Intermittent Fasting - PROS and CONS

Is it good for me? Does it work?

Let’s cut the chase, the secret of any type of diet is creating a calorie deficit, hence by introducing time restricted eating in our routine, one eats less calories, ie. creating a deficit.

So yes, intermittent fasting works, and research has shown us weight loss outcomes varying between 0.8 to 13% from baseline weight. However these outcomes were comparable to other calorie restricting diets, showing no significant benefits of one over the other. So the question is not whether intermittent fasting works but whether looking at the approach holistically would work for you as an individual.

Intermittent fasting consists of creating an eating window which is restricted to certain times of the day/ multiple days a week, separated by periods of fasting. Examples include the 16:8 method, eating for 8 hours and fasting for 16 hours and the 5:2 approach, eating for 5 days a week and then having 500/600 calorie meals on the remaining 2 days.

During the periods of fasting, the body would use the body’s glycogen stores to release glucose or use macronutrients (Carbs/Fat/Proteins) to make glucose for energy. The liver has enough glycogen stores to provide the body with glucose for up to 12 hours, after which the stores would become depleted and the body would start breaking down fats into what are known as ketones to provide energy, sparing some glucose for the brain.

That being said, to date few published studies have assessed the long term weight loss outcomes of intermittent fasting on humans and its risk factors since most studies were based on short-durations (8weeks to 1 year) and a limited number of people (N=10 to 244).

Since the role of intermittent fasting in weight loss is one of the most common questions I encounter in my profession, I’ve compiled a number of PROS and CONS to help clients make an informed individualised decision as to whether intermittent fasting would be a sustainable solution to their lifestyle.

  1. Improved blood glucose control, blood cholesterol
  2. Loss of lean muscle mass due to increased risk of low protein intake
  3. Weight loss
  4. Higher risk of weight regain
  5. No need to monitor calories- Simple to follow
  6. Difficult long term adherence
  1. Helps create consistent habits/ daily activities
  2. No changes in unhealthy dietary choices - accommodates habitual choices
  3. Reduces oxidative stress + inflammation
  4. Individual may overeat/binge to compensate for the upcoming fasting
  5. Ideal for people with a consistent daily routine - office hours, consistent break time, consistent training times
  6. Fasting period increases stress levels
  7. May help limit evening snacking/ emotional eating
  8. Difficulty to attend unplanned social events
  9. Difficult to adhere to if working inconsistent shift work, always changing pattern, night shifts, inconsistent break times, not able to train always at the same time of the day
  10. Need to plan schedules ahead, batch cooking to increase compliance when unplanned events crop up
  11. Links found with increased risk of eating disorders, anxiety and depression

To date, research showscomparable results of intermittent fasting to long term moderate calorie restricting diets. The decision to take the intermittent fasting approach, as with any other diet, needs to come from the individual and the person needs to engage with it. The role of the professional is there to help the client identify the potential barriers for it to be sustainable and practical.

Thank you for reading ! If you would like to discuss further get in contact with me to get started.

Helpful References;

  1. Bjerre, N., Holm, L., Quist, J. S., Færch, K., & Hempler, N. F. (2021). Watching, keeping and squeezing time to lose weight: Implications of time-restricted eating in daily life. Appetite,_ 161_, 105138.
  2. Cava, E., Yeat, N. C., & Mittendorfer, B. (2017). Preserving Healthy Muscle during Weight Loss. Adv Nutr,_ 8_(3), 511-519.
  3. Cienfuegos, S., Gabel, K., Kalam, F., Ezpeleta, M., Wiseman, E., Pavlou, V., . . . Varady, K. A. (2020). Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metab,_ 32_(3), 366-378.e363.
  4. Lowe, D. A., Wu, N., Rohdin-Bibby, L., Moore, A. H., Kelly, N., Liu, Y. E., . . . Weiss, E. J. (2020). Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Intern Med,_ 180_(11), 1491-1499.
  5. Stockman, M.-C., Thomas, D., Burke, J., & Apovian, C. M. Intermittent Fasting: Is the Wait Worth the Weight?
  6. Sutton, E. F., Beyl, R., Early, K. S., Cefalu, W. T., Ravussin, E., & Peterson, C. M. (2018). Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab,_ 27_(6), 1212-1221.e1213.
  7. Titmus, M. (2021). The influence of time-restricted eating on weight management and metabolic health. Retrieved 18/05/2022, from

Rebecca Micallef Dalli
Rebecca Micallef Dalli Member of the British Dietetic Association (SENR Registered), MSc. in Exercise and Nutrition Science. SENR Graduate Registrant
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