Let's Talk Fasting

Intermittent fasting has become a hot topic which garners a great deal of support in some circles and a great deal of apprehension in other circles. This week we will look at a study that examined the effects of a 12 week time restricted feeding window on study participants.


The term intermittent fasting is often used synonymously with time restricted eating. The truth is that there is a difference between the two. Intermittent fasting generally means 2-4 days a week of significantly reduced calories, or sometimes no calories at all for a period of a day or so. Time restricted eating is the practice of abstaining for food for a duration of a single day and restricting time to when you actually eat. The most popular time restricted pattern is a 16:8 window, where participants abstain from food for 16 hour periods and eat during an eight hour window. An example of this would be to eat dinner prior to 6 PM on a Sunday night and not consume calories again until 10 AM the following day. The subject then eats from 10 AM until 6 PM and repeats the process daily. Time restricted eating protocol is drastically different than intermittent fasting which often calls for a full day of 500 calories or less for 1 or more days.

This week I will be taking a look at a study done at the University of Illinois Chicago that examined the effects of time restricted eating on 23 obese patients. The study was titled “Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study,” and was published in 2018.

Study participants abstained from eating from 6PM until 10 AM the following day and then ate from 10 AM until 6 PM and repeated the cycle for 12 weeks. Investigators looked at the effects of this eating window on weight loss, lean mass, and certain metabolic and inflammatory markers compared to a matched historical control group (meaning a control group from a similar study that had been performed prior).


At the conclusion of 12 weeks the study’s authors noted that the time restricted window produced weight loss and reduction of systolic blood pressure compared to controls, however there were insignificant changes in fat mass, lean mass, and certain metabolic markers. The authors concluded that time restriction could be an effective means of weight loss BECAUSE IT PRODUCES A MILD CALORIC DEFICIT (just like we said last week).


Intermittent fasting and time restricted eating sometimes get lumped into the world of fad diets, and sometimes that is a rightful designation. Many advocates make some outrageous claims exaggerating the effects of IF and base their claims on studies often done on mice and other animal models. The truth is IF and time restricted eating have been shown to be a good tool for weight reduction and maintenance without the burden of calorie counting etc. It appears that it is effective as a result of the caloric deficit it creates which is very important. We do advocate for personal experimentation with IF and time restricted protocols in most healthy populations. Groups that should approach with caution are folks with blood sugar issues as well as elderly populations as they need to be cognizant of caloric and protein restriction due to factors such as sarcopenia. For healthy populations, we believe IF and TRE (especially TRE) can be effective tools in a program designed for healthy weight management.

Gabel K, Hoddy KK, Haggerty N, Song J, Kroeger CM, Trepanowski JF, Panda S, Varady KA. Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study. Nutr Healthy Aging. 2018 Jun 15;4(4):345-353. doi: 10.3233/NHA-170036. PMID: 29951594; PMCID: PMC6004924.

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