Time-restricted eating is often confused with intermittent fasting. While time-restricted eating involves eating food only at the specified window of hours – a component that can also be found in intermittent fasting – it also involves circadian rhythm element to it. In addition, intermittent fasting has an upper limit as to how much you are allowed to eat when you are not fasting; time-restricted eating does not have this limit.
Kessler et al. in a 2019 paper addresses how time-restricted eating aligns eating pattern to our circadian clock, the 24-hour internal clock that regulates our body's systems. The circadian system is coordinated by the suprachiasmatic nucleus (a structure in the hypothalamus, which is located in the brain), which sends signals to the organs, including those that are crucial in metabolism like the liver and the pancreas. Perhaps then time-restricted eating may influence other organs and metabolic health.
A study published in 2018 by Sutton et al. compared eight men with prediabetes on a control diet, where they were allowed to eat in a 12 hour period, and an early time-restricted eating diet (eTRF), where they were allowed to eat in a 6 hour period before 3:00 pm; the eTRF consequently ate dinner before 3:00 pm. They continued this for 5 weeks, and the participants switched in both groups switched conditions for the next 5 weeks.
The results showed that eTRF did not have a benefit to the glucose levels in these men, there was improvement in insulin sensitivity, which means that the body's cells had a higher sensitivity to insulin and that they required less amount of insulin (a hormone made by the pancreas that allows your body to use sugar for energy or store it for future use) to lower the blood glucose levels.
This is important because prediabetic individuals are at risk of developing diabetes, which is when the blood glucose levels are too high. However, the study showed that "5 weeks of eTRF did not improve glucose levels" but that it "lowers blood pressure and oxidative stress" and "lowers the desire to eat in the evening, which may facilitate weight loss."
There appears to be some benefit for time-restricted eating in this study, but it is certainly not conclusive because of the small sample size and cannot be generalized because all of the participants were prediabetic. Not eating after 3:00 pm also seems unrealistic, given that much of our culture resides around socializing over dinner with friends and family.
Nevertheless, more research is necessary to elucidate clearer benefits and drawbacks of time-restricted eating.
