Fasting. It’s the new thing!
Only, new it’s not.[1]
Back in the days of ancient Greece (500 BCE-ish), philosopher Pythagoras encouraged followers to fast if they wanted to make contact with the supernatural world.
The Bible is littered with references to fasting, and many Muslims don’t eat or drink from dawn to sunset during the holy month of Ramadan. Some Buddhist monks fast for 18 or more hours a day, and there are a select number of fasting days on the Jewish calendar.
The ties between fasting and religion run deep.
Nowadays, we talk about fasting when we ask what’s for breakfast. That’s when we rise from our sleep and break our overnight fast by eating, well, breakfast.
The buzz online and in the news is all about intermittent fasting, or time-restricted eating. Both of which may improve blood sugar levels and contribute to weight loss.[2] Our little prediabetic ears perked up when we heard this.
What is intermittent fasting (IF), exactly? Are time-restricted feeding (TRF) and IF basically synonyms? What about intermittent energy restriction (IER) and continuous energy restriction (CER), or time-restricted eating (TRE)?
It’s terminology overload.
The terms and the definitions vary a bit, depending on who’s talking. Here’s a glossary to help us keep it all straight:
Continuous Energy Restriction (CER)
This is the conventional version of a diet, where we’re severely restricted in the number of calories we can consume 24/7. No on-and-off, or intermittent, fasting.
Intermittent Energy Restriction (IER)
Time periods in which we eat little (maybe 500 calories) to nothing at all. These time periods generally run from 16 hours to 48 hours.
Intermittent Fasting (IF or IMF)
IER and IF are the same. Time periods in which we eat little (maybe 500 calories) to nothing at all. These time periods generally run from 16 hours to 48 hours.
Periodic Fasting (PF)
PF is extended IF, running a time period of two days to three weeks, give or take, during which little (maybe 500 calories) or nothing is eaten.
Time-Restricted Eating (TRE)
A limited block of hours each day in which we can eat, typically 8-10 hours.
Time-Restricted Feeding (TRF)
This term is used for people or animals. It refers to a limited block of hours each day in which the animal (or person) eats, typically 8-10 hours.
A tiny study published in Cell Metabolism[3] swept the holiday chatfests. By just changing how many hours a day we eat, we might see an improvement in our weight and our blood sugar levels.
In this small study, participants ate within a 10-hour window each day for three months. And only within that window of time. Because they only ate during that block of time, they fasted the other 14 hours of the day.
In general, they lost weight, lowered their blood pressure, and found their fasting blood sugar and A1C numbers were improved.
There’s a larger study in the works,[4] funded by the NIH, that follows up on this subject. But we’ll have to wait a few years for the results.
While we’re waiting, talk with your healthcare provider about intermittent fasting, or time-restricted eating. See if it’s something they feel you could tolerate and if so, and you want to try it, determine the length of time that would be safe for you to eat/not eat.
[1] Western Journal of Medicine, Fasting: The History, Pathophysiology and Complications, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1274154/pdf/westjmed00207-0055.pdf, (January 2, 2020).
[2] Ageing Research Reviews, Impact of intermittent fasting on health and disease processes, https://www.sciencedirect.com/science/article/pii/S1568163716302513, (January 2, 2020).
[3] Cell Metabolism, Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome, https://www.cell.com/cell-metabolism/fulltext/S1550-4131(19)30611-4, (January 2, 2020).
[4] UC San Diego Health | Clinical Trials, Impact of Time-Restricted Feeding (TRF) on Glucose Homeostasis and Mitochondrial Function in Patients with Metabolic Syndrome, https://clinicaltrials.ucsd.edu/trial/NCT04057339, (January 2, 2020).