I started researching and talking about Time restricted eating (TRE) more than 20 years ago and often include it in my Gut Health and Weight Loss talks as a fantastic tool for improving the gut and weight loss at the same time. However, there are many more potential benefits which should be enough reason for everyone to implement it into their lives as I have done.

TRE has been a part of human culture from the beginning only until the last 5 decades or so in developed countries with the advent of ready available and abundant foods and as a result the epidemic of chronic metabolic illnesses and poor health. Fasting and TRE, in one form or another, has been employed for various lengths of times safely for thousands of years especially for religious reasons but no more than ever for health benefits. 

TRE is not necessarily about changing the type of food you eat, although this is advisable for many people as well but about changes in the timing of food intake, without caloric restriction. TRE has many potential health benefits and allows a ketogenic state during the 12-18 hours without food intake (including the time of sleep) although most studies refer to a 16-18 hour non-eating window. Allowing a window of 6–8 h over a 24-h period, with no calorie consumption outside of this window, as opposed to the long hours, often 15-17 of food intake common in most Western countries. 

TRE is an attractive strategy, allowing the combination of a ketogenic state during the 16 h of noneating and healthy eating to achieve the most beneficial state. TRE is a more viable option than calorie counting or calorie restriction since it does not require the reduction of overall caloric intake during the day, instead compress the window of unrestricted energy consumption within a 24-h time period, with a large part of the food restriction period taking place during sleep. 

While there are many health benefits TRE can help reset you body’s metabolic health and timing.  Our regular daily eating schedule is one of the main determining factors of diurnal rhythms in metabolic pathways. Implementing TRE where food consumption is confined to an 8-h window helps rest your body’s biological clock (circadian rhythm) and prevents the harmful effects of metabolic diseases caused by high-fat, high-sugar diets without limiting daily caloric intake. The brain and nearly every peripheral organ have circadian timekeeping mechanisms that impact their function. 

Late dinner times, late-night snacking, or eating during the night can chronically disrupt circadian rhythms, lead to metabolic dysfunction and disease including obesity. Shortening the length of the eating window and skewing intake away from the evening/night helps to re-align food intake with the natural 24-h human cycle of feeding and fasting. TRE thereby resets the body’s peripheral clocks. In one study of 99 healthy individuals or those with obesity, self-reported sleep quality but not duration was improved after following 16:8 TRE for 12 weeks.

Studies have overwhelmingly shown the benefits for reducing metabolic illness including lowering excess weight, hypertension, high blood sugar, diabetes and more without any negative side effects. In animals, TRE actually reduces whole-body fat accumulation and inflammation while improving glucose tolerance, reducing insulin resistance, improving homeostasis, and restoring cholesterol balance. Preliminary evidence suggests that TRE reduces fat in ‘ectopic’ regions of the body (e.g., visceral, liver, intermuscular) which also are much more strongly linked to the primary risk of cardiovascular disease and certain cancers. 

Studies have also shown the potential for TRE to improve chronic glucose control. Among 2212 women with elevated BMI, each 3-h increase in habitual overnight fast time was associated with 19% lower odds of elevated hemoglobin A1c (blood sugar). While a meta-analysis of 10 TRE intervention studies with 238 participants also reported a reduction in fasting blood glucose of around −2.96 mg/dL.

Another meta-analysis of six TRE studies with 97 participants found significant decreases in systolic blood pressure of −3.07 mmHg, and −1.77 mmHg for diastolic blood pressure, independent of weight loss.

Allowing the digestive tract time periods without food, forces the body to burn fat during these times instead of using energy from a continuous glucose supply. In the absence of food ingestion, a metabolic change occurs which forces the liver to produce ketones from the metabolism of body fat when glucose is inaccessible. As well as acting as fuel, ketone bodies are signalling molecules that have significant positive effects on major functions of the cells and organs, including the brain. 

The regular exposure to a fasting period induced by TRE also has benefits for cellular health. Growing evidence suggests that TRE reduces oxidative stress and inflammation, both of which are involved in the development and progression of all chronic illness. Studies have shown decreases in the proinflammatory markers interleukin (IL)-6 and IL-1β independent of weight loss. 

Regular fasting activates cell signalling pathways and integrated adaptive responses between and within organs, that increase the expression of antioxidant defenses, DNA repair, protein quality control, mitochondrial biogenesis, autophagy, and reduces inflammation. This adaptive response confers resistance to oxidative and metabolic stress and the removal/repair of damaged molecules. An increasing number of studies are showing the benefits of TRE with cancer prevention and treatment.

In a study of breast cancer survivors having a non-eating period of less than 13 hours (eating for up to 11 hours), lead to a 36% higher risk of breast recurrence compared to women who fasted for longer periods. In addition to the total length of the nightly fasting duration, eating after 8 pm appeared to be a potential determinant of risk, as it was associated with increased chronic inflammation and higher BMI among these breast cancer survivors.

TRE has also been shown to have major benefits of reducing the risks for people who have cardiovascular operations. In a study of patients undergoing cardiac catheterization without prior myocardial infarction or heart failure reported that prolonged nightly fasting was associated with a 71% reduced incidence of heart failure and a 31% reduced incidence of myocardial infarction.

Other side benefits of TRE include the subconscious reduction of snacks and overall calories. One study with overweight but otherwise healthy individuals adhering to TRE significantly reduced their daily caloric consumption mainly by eliminating late-night alcohol and snacks, which resulted in sustained weight loss for up to one year. Studies with time-restricted eating in overweight or obese humans have consistently shown a reduction in overall calorie consumption which led to decreased bodyweight and fat mass. TRE typically results in 20–30% spontaneous caloric restriction and mild weight loss of 1–4% over 1–12 weeks without the need to count calories. There is just less time to eat all the food we normally do.

TRE is a simple and very effective strategy that we can all apply to our lives with minimal impact on the quality of our lives.

References

Christensen, R.A.G.; Kirkham, A.A. Time-Restricted Eating: A Novel and Simple Dietary Intervention for Primary and Secondary Prevention of Breast Cancer and Cardiovascular Disease. Nutrients 2021, 13(10), 3476; https://doi.org/10.3390/nu13103476 

Brain–Gut–Microbiome Interactions and Intermittent Fasting in Obesity
Nutrients 2021, 13(2), 584; https://doi.org/10.3390/nu13020584