The Study:  Intermittent fasting and weight loss: Systematic review                 

The Facts:

a. The authors examined the evidence for using intermittent fasting (IF) as a method of weight loss.

b. This is a review of the literature and the authors selected 41 articles which were generated from 27 trials.

c. The trials varied in quality of evidence generated, length of trial and number of subjects.

d. The authors note the recent interest in intermittent fasting. (see SIB# 395 for our previous review of one such article.)

e. Two of the most common variations of intermittent fasting are: 1) Fasting for 16 hours of the day and then eating all calories for the day within the remaining 8 hour period and 2) to fast (or eat only a small amount, often 500 calories or less) on 2 non-consecutive days and then eat as desired on the remaining days of the week.

f. All the trials included in this review showed weight loss but the amount varied from 0.8% to 13.0%.

g. “Twelve studies used calorie-restricted diets as a com­parator to IF and found equivalent weight loss in both groups.”

h. The authors indicate that intermittent fasting “is a moderately successful strategy for weight loss, it shows promise for improving glycemic control.”

i. But the authors note that in diabetes there is a risk of hypoglycemia.

j. They also cited the finding of one study on blood sugar, “Kahleova et al compared a daily fast of at least 16 hours to caloric restriction (n = 54). Both groups experienced decreases in insulin levels but IF participants had significantly lower fasting glucose levels (-0.78 mmol/L vs -0.47 mmol/L, P < .05). Increased oral glucose insulin sensitivity, decreased C-peptide levels, and decreased glucagon levels were also statistically significantly greater in the IF group. The decrease in hemoglobin A1C level was similar between the IF and calorie-restricted groups—a 0.25% decrease over 12 weeks (level I evidence).” 

k. The authors indicate, “No serious adverse events were reported in the 27 IF trials.”

l. The authors conclude, “Intermittent fasting shows promise as a primary care intervention for obesity, but little is known about long-term sustain­ability and health effects.”  

Take Home:

There were a lot of different methods and time intervals that were included in this paper  therefore it is difficult not to get into “ apple and oranges” types of comparison problems. The authors note that the subjects lost weight in all the studies but the amount varied greatly as did the time and methods. At this point it appears the use of IF may shows some promise.

 Reviewer's Comments:

We’ve reported on IF before and for the reader you know that I have been doing this on a basis of eating an average of around four hours a day. I have lost weight but have had difficulty recently as the current virus problem has closed our gym and limited the places we can walk. But I am very interested in this method and I think we will see a lot more study in this area in the future.

Reviewer:  Roger Coleman DC

Editor: Mark R. Payne DC 

Reference:  Welton S, Minty R, O’Driscoll T, Willms H, Poirier D, Madden S, Kelly L. Intermittent fasting and weight loss: Systematic review. Can Fam Physician 2020 Feb;66(2):117-125.

 

Link to Abstract: https://www.ncbi.nlm.nih.gov/pubmed/32060194

Link to Full Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021351/pdf/0660117.pdf