Can Intermittent Fasting Work for You?

Intermittent fasting (IF) has been a buzz phrase in the diet world the past several years after Kate Harrison had her “5:2 Diet” book published in 2012. She is a journalist and novelist who had struggled with her weight, and found that fasting (eating only 25% of her caloric needs) two days per week helped her lose weight. (1) Thankfully, research started to see if intermittent fasting could actually promote weight loss - even more than traditional calorie restriction diet plans, and furthermore to see if it could help people with diabetes, high cholesterol, inflammation and more.

What is Intermittent Fasting?

There are basically two types of IF - one is fasting for a day or more - either consecutive or alternating days and the other is restricting the time you eat during the day - usually between 8 and 12 hours.

Is It Safe?

There is no research at this time that says it’s unsafe. However, It is not recommended for those who have a history of an eating disorder (as the restrictive nature may trigger a relapse) or growing children, teens, and pregnant or breastfeeding women. Those with diabetes should be extra careful also, especially if they have type I diabetes or take a diabetes medication - they could get a life threatening low blood sugar if they significantly reduce their food intake while taking these medications.

Will You Lose Weight?

Maybe, probably. However, you lose the same amount of weight with a typical calorie restricted meal plan (eating 75% of your needs, e.g. 1500 calories per day, everyday), as you do with an alternate day fasting diet. A July 2017 study in the JAMA “Internal Medicine” journal showed that alternate day fasting showed no superior results when compared to daily calorie restriction with weight loss, or other cardiac risk factors, like cholesterol levels, blood pressure, insulin resistance, and inflammatory markers. The non-fasting “feast” days were also limited to 125% of calorie needs - so not necessarily allowed to “eat whatever,” either. (2) The biggest problem with this study and then recommending this intervention is the adherence to the fasting days. The dropout rate was highest in the alternate-day fasting group at 38%, relative to the daily calorie restriction group at 29% and control group at 26%. Another study by Appleton & Baker, “reported that in women, a 2-day fast resulted in distraction, but not hunger, and was associated with lower mood and perceived work performance compared with 2 days prior to and following the fasting period.” (6) So picking a diet, meal plan, or eating lifestyle that you can stick with (and not suffer through) is one of the most important factors to consider.

There was more research in November 2018 with the HELENA trial in Germany that showed similar weight loss results. The 2 groups lost about the same amount of weight; the “5:2 Diet” group and the daily 20% calorie restricted group both reduced their visceral (unhealthy belly fat) and liver fat. But the “5:2 Diet” group did not lose more than the conventional daily calorie restricted diet group. (5) Again, the thing to consider is what works for you - it may be easier to restrict and count your calories 2 days a week, vs all 7 days. Just remember, you can’t eat endless amounts of unhealthy foods the other 5 days, and furthermore, once you decide to stop, you still have to continue to eat moderate amounts of healthy foods to keep the weight off.

As for restricting the amount of time you eat during the day, and for eating during daylight hours only, there are limited, quality studies with humans. However, in 2016, there was a “6-week controlled research in the “American Journal of Clinical Nutrition,” where researchers “observed no benefit with respect to weight change, glycemic control, lipids, or inflammatory markers for the group omitting the breakfast meal.” In this study, when participants did not eat breakfast (had a prolonged night-time fast) they had higher hunger hormones (ghrelin) before lunch, but they did not eat more at lunch, which is positive. However, even though they skipped breakfast and ate the same amount at lunch, their blood sugar and their insulin levels were higher 2 hrs after lunch - not the results for which one is looking to achieve. (3)

There is a decent amount of epidemiological research (studies that look at populations to see if there is a relationship between exposure and the risk of diseases) that shows that night shift work, and eating at nighttime, is related to increased risks of obesity, diabetes, cardiovascular disease, and cancer (particularly breast cancer), and increased odds of an elevated HgbA1c (a test to measure blood sugar average over time - used to diagnose and monitor diabetes). (4) So despite not getting the extra weight loss results one is looking for, at least they can feel positive that they may still reduce their health risks when cutting out nighttime eating.

What’s really cool in this research is that fasting diet regimens appear to have positive impacts on the gut microbiota. Giving the gut, metabolism, and body time to rest, repackage and restore has shown to improve the gut microbiome in early research. This may positively support achieving a healthy weight, by not only improving gut health, but also potentially reducing the risk of many other inflammatory diseases related to the brain-gut pathway. (4)

The Bottom Line Is…

Intermittent fasting, whether alternate day or time restricted feeding can be a safe method to try to lose weight, for most people. However, and if you can stick with it, the research results so far don’t show that it is anymore productive for weight loss than a daily calorie restricted diet, which appears to be more sustainable and realistic than IF. You may find that a combination of multiple tools and methods, along with support and advice, can help you reach your weight loss goal - and keep it off! If you want to try a fasting regimen as one of many tools to eat well and lose weight, go for it! I would even love to support you with this!

Always (please!) have caution if you feel that this, or any weight loss diet for that matter, will cause you any harm, including stress, anxiety, depression, or possibly disordered eating behaviors. We do know that obesity is linked to heart disease, cancer, and type 2 diabetes and it is worthwhile to consider losing weight if you’re overweight or obese. Although, weight isn’t everything - you can still reduce your health risks by eating healthy foods, exercising, not smoking, and managing your stress. We also know that the quality of the foods in our diet is important to promote health and reduce disease risk - so we shouldn’t look at any of these fasting regimens and even weight as the sole indicator of health, i.e. you should still eat healthy foods no matter your weight or weight goals.

As always, if you have any questions, please contact me at Bridget@nutribridgerd.com

(1) https://the5-2dietbook.com/basics

(2) https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2623528

(3) Chowdhury EA, Richardson JD, Holman GD, Tsintzas K, Thompson D, Betts JA. 2016. The causal role of breakfast in energy balance and health: a randomized controlled trial in obese adults. Am. J. Clin. Nutr. 103: 747–56

(4) https://www.annualreviews.org/doi/full/10.1146/annurev-nutr-071816-064634?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed

(5) https://www.sciencedaily.com/releases/2018/11/181126115842.htm

(6) Appleton KM, Baker S. 2015. Distraction, not hunger, is associated with lower mood and lower perceived work performance on fast compared to non-fast days during intermittent fasting. J. Health Psychol. 20:702–11a