Eating and sleeping are two essential behaviors that humans engage in, on a daily basis [2]. Caloric restriction is known as one of the ways to live a long life. Several studies and experiments have shown that eating less increases the lifespan of animals by reducing the rate of aging. Reducing calorie intake reduces weight, in addition to lowering blood pressure and inflammation levels, and also regulates blood sugar in a better manner [3]. Furthermore, another study added that along with the amount of food eaten, the timing at which it is eaten is also important for extending the life span. Acosta-Rodríguez et al. [1] reported that a four-year experiment on hundreds of mice showed that eating only during active hours of the day contributes to an increase in life expectancy. The researchers examined these mice by dividing them into six groups and used an automatic feeder to control the amount of food and meal times. One group allowed them to eat as much as they wanted, while the other five groups were given 30%–40% less feed. These groups were further divided into five sub-groups according to the meal intervals. While two groups were supplied with an intensive daily feeding amount within 2 hours from the start of either the day or night, the other two groups ate at regular intervals of 90 minutes within 12 hours during the day or night and starved for the rest of the time. The last group was given a steady supply of feed once every 160 minutes for 24 hours a day, regardless of biological rhythm.

The classification of meal supply methods was performed to investigate the influence of time-based meal plans such as intermittent fasting and biological rhythm along with the amount of food consumed. The average life expectancy of mice that ate less was 10% longer. The group that ate only at night when the mice were active had a longer lifespan compared to the group that ate meals in daytime. The mice that consumed less feed during the day had a 20% increase compared to the mice without restrictions on feed, whereas the mice that consumed food for only a short period of time at night showed a 35% increase in their lifespan, respectively. The lifespan of mice that ate only at night was nine months longer compared to that of the mice that ate without any time-bound restrictions, with an average lifespan of two years.

The results of this study also have great implications for the recent trend of intermittent fasting. It suggests that eating for a short period of time during the day and not eating at all at night is a healthy way to live a long life in humans. This study emphasizes the importance of adopting a lifestyle according to the circadian rhythm to maintain good health. It further describes the flaws of previous studies that did not consider the issue of timing, particularly, circadian rhythm. In the future, thus, to conclude, research designs based on circadian rhythms should be considered in future biomedical studies.