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Intermittent Fasting

Intermittent Fasting

If you think about how humans have been eating for centuries, it has likely included some "natural" intermittent fasting. For example, people have typically consumed their last meal of the day by 5 or 6 PM as daylight ended, gone to sleep, and then awoke at sunrise to consume their first meal before beginning their day's workbreaking the nighttime fast. Therefore, there was a natural intermittent fast of 12 to 14 hours. As we have evolved, we are up late at night or early in the morning, and eating patterns have become scattered. So here is a new approach to weight loss: limiting the time of eating throughout the day so there is a period of prolonged fasting, allowing the metabolism to reset.

In a recent publication in Cell Metabolism, subjects were allowed to eat whatever they wanted but only between 8 AM and 6 PM, creating a 10-hour eating window and a 14-hour fasting window in each 24-hour period. Nineteen subjects enrolled in the 3-month study, and multiple outcome measures were analyzed. Results showed statistically significant systolic blood pressure and body fat reductions, LDL cholesterol reductions, an average weight loss of 7 pounds, and an average waist circumference decrease of 4 cm. There were also reductions in glycated hemoglobin (A1C) and fasting blood glucose, but these measures were not statistically significant. Study subjects logged intake data into apps and analysis showed they did not skip meals, but rather compressed the time between meals. The subjects' daily intake while intermittent fasting was about 200 calories less than in the pre-study period. This was assumed to be due to the time-restricted eating schedule. During follow-up, researchers contacted the student participants and found that only 5 of the 19 were still adherent to the restricted calorie consumption time window.

In a critique of the study, Dr F. Perry Wilson ponders several issues, the greatest being that the study design did not have a control group. Participants knew they were being studied, so one may consider the "Hawthorne effect" as a possibility as to why the subjects were compliant, and the results promising. On the upside, limiting the hours when a person consumes calories to create a daily fasting period of about 14 hours is a very simple approach to changing eating behavior. This alone seemed to reduce caloric intake daily, which was significant over time. Other diets are much more complicated and may require weighing and measuring food or balancing macros such as proteins, carbohydrates, and fats. Ultimately, behavior changes to eating routines are more likely to be successful if they are simple.

  • Wilkinson M, Manoogian E, Zadourian A, et al. Ten-hour time-restricted eating reduces weight, blood pressure, and atherogenic lipids in patients with metabolic syndrome. Cell Metabolism. 2019 [Epub ahead of print].
  • Wilson FP. Intermittent fasting may help treat metabolic syndrome. Accessed December 17, 2019.

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Filed under: Cardiometabolic, Miscellaneous, Preventive Medicine, Public Health

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