Intermittent fasting, simple and effective

In

,

By

Yassine Damil

Episode 10

TL;DR
  • Intermittent fasting alternates periods of fasting and meals, with forms such as periodic fasting and time-restricted feeding (TRF).
  • By reducing the food window, TRF creates a caloric deficit, facilitating weight loss without changing eating habits too much.
  • Recent studies show that TRF can induce weight loss similar to that achieved by counting calories. Other benefits are also expected.
  • However, TRF may result in a loss of lean body mass, due to a possible time constraint limiting adequate protein intake.
  • Intermittent fasting can be dangerous for some people, particularly those with diabetes or taking medication. Caution is therefore called for…

I practiced intermittent fasting for over a year (and in its best variant, as we’ll see later). My verdict? Before answering your question, I’d like to borrow a favourite phrase from someone close to me: “What’s the point?” In fact, in my case, it wasn’t so much to lose weight as to reap the other health benefits (and, incidentally, to ‘rest’ my – always irritating – digestive system before going to sleep). So? Patience…

What is intermittent fasting?

Intermittent fasting1 is a feeding practice that consists of alternating periods of fasting and periods of eating in a specific pattern. Rather than a diet (what to eat) or a regimen (how much to eat), it’s an eating pattern that can take different forms (or simplifying: when to eat):

  • Periodic fasting: This is a complete fast (also known as hydric fasting, since water intake – without calories – is essential) or a ”modified” fast (where 25% of the usual daily energy intake is allowed) over a minimum period of 24 h. Its best-known variants are alternate fasting (1 day out of 2) and “5:2” (2 days out of 7, non-consecutive).
  • Time-restricted feeding or TRF: Fasting followed by an eating window of a few hours, intended to bring us closer to our natural circadian cycle. Its most popular variant is the “16:8”, the placement of the 8-hour eating window being the subject of debate between metabolic efficiency (morning) and social practicality (convivial evening meal).

It’s the TRF that interests us here. Why? Because it’s the easiest to implement (periodic fasting is psychologically more difficult to follow), and that’s the main argument in favor of the practice!

Counting hours rather than calories

We generally eat over a window of 12 to 14 h. Removing 6 of them almost automatically creates a calorie deficit: less time to eat means less intake at the end of the day. The advantage over dietary regimens, which are fundamentally focused on calorie restriction (i.e. calorie counting to induce calorie deficit), is that you don’t change anything in your diet during the aforementioned window.

Does it work for weight loss? Pretty much! Some results were already positive, but not necessarily conclusive, since we couldn’t determine whether they were the result of a short-term2 transition effect or of calorie restriction3. However, a study published in 20224 proposed a one-year follow-up. The induced weight loss (5%) was similar to that achieved by counting calories.

The only – not insignificant – criticism I could make is that participants benefited from individualized nutritional support (with behavioral and cognitive techniques that are also known to be effective, as recalled in the previous Episode)! Another possible, but this time understandable, criticism was that the eating window was from 12 p.m. to 8 p.m.: this was to limit the drop-out rate from the protocol. However, a study5 had demonstrated the metabolic benefits of eating in the morning, i.e. from 8 a.m. to 4 p.m., which was the variant I had used…

Could there be other benefits? On this point, we must be wary of conclusive studies… on animals (e.g., on cancer or ageing prevention). And we’ll leave aside those that are more related to the calorie deficit that is a consequence. So, what can we say today?

  • According to one study6, intermittent fasting reduces insulin resistance and therefore blood glucose levels, which explains the weight loss effect (low blood glucose makes body fat more accessible). An older study7 identified a 5-fold increase in growth hormones, which has the same effect on weight.
  • A 2020 meta-analysis8 shows a reduction in markers of inflammation, a key factor in many chronic diseases. To this can be added another from 20219 on cardiometabolic risk factors.
  • Moreover, for the more curious among you, I invite you to take a look at a more recent and fascinating study10 highlighting the influence of periodic fasting on gene expression…

An effective approach, but not for everyone…

It didn’t seem to be particularly addressed in the weight loss study already cited, but a previous one from 202011 highlighted the fact that the group who followed the TRF protocol lost 2 times more lean mass than normal (when you lose weight, you also lose muscle). One possible explanation is that the time constraint does not allow for sufficient consumption of proteins, the many benefits of which we have already praised. One solution12 to mitigate this effect would be to combine fasting with muscle strengthening.

Let’s get back to my specific case. Well, as I said, I wasn’t aiming to lose weight, but rather to build muscle mass, in parallel with regular training. I had noticed that I was still managing – albeit more slowly – to improve my performance but that I was no longer able to gain muscle (hypertrophy). And even then, my training sessions took place in the morning, i.e. during my eating window. I don’t know what would have happened if I’d been fasting. What’s certain is that the protocol forced me to have 2 real meals rather than 3, and that it was quite difficult to ‘fit in’ more than 60 g of proteins per meal (to give you an order of magnitude, that’s 2 chicken cutlets but also 8 eggs !). And I’m not talking about my friends who reproached me for not ordering anything at the restaurant in the evening… But overall, I felt fine!

Finally, I’d like to point out that intermittent fasting, whatever form it takes, can be dangerous for people suffering from certain illnesses, such as diabetes. Those taking medication for blood pressure or heart disease may also be more prone to imbalances of sodium, potassium and other dietary minerals during longer-than-normal periods of fasting… Also, it would be inadvisable for teenagers, people with eating disorders, women desiring to conceive, already pregnant or breast-feeding. In short, as always, when in doubt, consult a doctor!

Remember, if you want to lose weight, intermittent fasting is an effective solution, especially time-restricted feeding. It’s not necessarily efficient, since it leaves you free to cover all your dietary needs or not. The benefits are actually more behavioural than metabolic. To avoid losing muscle, make sure you optimize your protein intake. I haven’t mentioned a dimension that perhaps deserves a specific focus: what about the mental (or spiritual) benefit of the practice, which this form of asceticism emphasizes (and which is found in several religions)?

Here’s a personal hack: adapt your last meal (before fasting). Your ability to easily manage hunger will depend on how slowly you digest it. To help you do this, I recommend enriching your meal with fiber, protein and healthy fats, all of which are highly satiating…

Fun Fact

For those of you like me who wonder how long you can go without eating (but drinking), in other words, by fasting, there’s a Guinness record13 for that. Angus Barbieri is a Scotsman who fasted for 382 days, from June 1965 to July 1966. He drunk tea, coffee, sparkling water and vitamins (after all!), while living at home in Tayport, Scotland. As a result, he lost 293 lb or 133 kg (dropping from 214 to 80.74 kg). As you’d expect, how long you can keep it up depends on your starting weight… And, unrelatedly, I couldn’t find a Guinness record for who consumes the most (Guinness)…

Going further

References

  1. https://en.wikipedia.org/wiki/Intermittent_fasting ↩︎
  2. Cienfuegos S, Gabel K, Kalam F, et al. Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metab. 2020;32(3):366-378.e3. doi: 10.1016/j.cmet.2020.06.018. https://pubmed.ncbi.nlm.nih.gov/32673591/ ↩︎
  3. Liu D, Huang Y, Huang C, et al. Calorie Restriction with or without Time-Restricted Eating in Weight Loss. N Engl J Med. 2022;386(16):1495-1504. doi: 10.1056/NEJMoa2114833. https://pubmed.ncbi.nlm.nih.gov/35443107/ ↩︎
  4. Zhang Q, Zhang C, Wang H, et al. Intermittent Fasting versus Continuous Calorie Restriction: Which Is Better for Weight Loss?. Nutrients. 2022;14(9):1781. Published 2022 Apr 24. doi: 10.3390/nu14091781. https://pubmed.ncbi.nlm.nih.gov/35565749/ ↩︎
  5. Jakubowicz D, Barnea M, Wainstein J, Froy O. High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity (Silver Spring). 2013;21(12):2504-2512. doi: 10.1002/oby.20460. https://pubmed.ncbi.nlm.nih.gov/23512957/ ↩︎
  6. Barnosky AR, Hoddy KK, Unterman TG, Varady KA. Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Transl Res. 2014;164(4):302-311. doi: 10.1016/j.trsl.2014.05.013. https://pubmed.ncbi.nlm.nih.gov/24993615/ ↩︎
  7. Hartman ML, Veldhuis JD, Johnson ML, et al. Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men. J Clin Endocrinol Metab. 1992;74(4):757-765. doi: 10.1210/jcem.74.4.1548337. https://pubmed.ncbi.nlm.nih.gov/1548337/ ↩︎
  8. Wang X, Yang Q, Liao Q, et al. Effects of intermittent fasting diets on plasma concentrations of inflammatory biomarkers: A systematic review and meta-analysis of randomized controlled trials. Nutrition. 2020;79-80:110974. doi: 10.1016/j.nut.2020.110974. https://pubmed.ncbi.nlm.nih.gov/32947129/ ↩︎
  9. Yang F, Liu C, Liu X, et al. Effect of Epidemic Intermittent Fasting on Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Front Nutr. 2021;8:669325. Published 2021 Oct 18. doi: 10.3389/fnut.2021.669325. https://pubmed.ncbi.nlm.nih.gov/34733872/ ↩︎
  10. Lilja S, Stoll C, Krammer U, et al. Five Days Periodic Fasting Elevates Levels of Longevity Related Christensenella and Sirtuin Expression in Humans. Int J Mol Sci. 2021;22(5):2331. Published 2021 Feb 26. doi: 10.3390/ijms22052331. https://pubmed.ncbi.nlm.nih.gov/33652686/ ↩︎
  11. Lowe DA, Wu N, Rohdin-Bibby L, et al. 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 [published correction appears in JAMA Intern Med. 2020 Nov 1;180(11):1555] [published correction appears in JAMA Intern Med. 2021 Jun 1;181(6):883]. JAMA Intern Med. 2020;180(11):1491-1499. doi: 10.1001/jamainternmed.2020.4153. https://pubmed.ncbi.nlm.nih.gov/32986097/ ↩︎
  12. Moro T, Tinsley G, Bianco A, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. 2016;14(1):290. Published 2016 Oct 13. doi: 10.1186/s12967-016-1044-0. https://pubmed.ncbi.nlm.nih.gov/27737674/ ↩︎
  13. https://www.guinnessworldrecords.com/world-records/78789-longest-survival-without-food ↩︎