The Study: Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes.            

The Facts:

a. The authors note that while there have been health benefits attributed to intermittent fasting (IF), these benefits may be due to the weight loss frequently associated with IF.

b. The authors state, “We conducted the first supervised controlled feeding trial to test whether IF has benefits independent of weight loss by feeding participants enough food to maintain their weight.”

c. “We performed a five-week, randomized, crossover, isocaloric and eucaloric controlled feeding trial testing eTRF (Early Time Restricted Feeding) in men with prediabetes.

d. This was a small study. Only 8 subjects that completed the study (four subjects dropped out). The authors cited problems with recruiting as the subjects had to be able to eat all meals under supervision, to ensure compliance to the study parameters.

e.. The participants had a six hour period each day in which they could eat for a period of 5 weeks.

f. They ate dinner before 3pm as the authors felt there might be an effect from circadian rhythms.

g. They found that there was a lowering of blood pressure of 11 mm Hg (+/- 4 mm) of the systolic and 10mm (+/- 4mm) of the diastolic.

h. “Although five weeks of eTRF did not improve glucose levels, it dramatically lowered insulin levels and improved insulin sensitivity and β cell responsiveness.”

i. Other interesting findings included; an increase in morning heart rate though it did not reach statistical significance, reduced oxidative stress (8-isoprotane) although there did not appear to be any reduction of inflammatory markers, an increase in triglycerides but no change in LDL or HDL cholesterols, and substantial reductions in hunger levels and capacity to eat during the evening hours.

Take Home:

This small study showed a decrease in blood pressure and insulin levels and improved insulin sensitivity. There were also other changes that merit further study.

Reviewer's Comments:

So what do I think about this study? First I think that the idea to see if IF has beneficial effects without weight loss is a good thing to study. I have to tell you that I always worry about studies that show big changes in blood pressure when we don’t expect it as there are so many things that affect blood pressure. So I like to see multiple studies to confirm blood pressure changes. But it would be really great if that is confirmed by more studies. I know the number of subjects is small due to the difficulty in recruiting as noted above. But I found this study interesting largely because of the lowered insulin levels and the improvement in insulin sensitivity. Someone I know keeps bending my ear about insulin so this one’s for you. I look forward to seeing more studies in this area.

Reviewer:  Roger Coleman DC 

Editor’s Comments: Improvements in insulin sensitivity are potentially a big factor in weight loss and other aspects of metabolic health. As noted above, while all of this needs more study, this paper is interesting in concept because the role of weight loss has been removed as a factor in the metabolic changes.

Editor: Mark R. Payne DC

Reference: Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab. 2018 Jun 5;27(6):1212-1221.e3. doi: 10.1016/j.cmet.2018.04.010. Epub 2018 May 10.  

Link to Abstract: https://www.ncbi.nlm.nih.gov/pubmed/29754952

Link to Full Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5990470/