Meaning to say, if we were to live in complete darkness (like in caves), we would fall into cycle of days that last up to 25 hours.
In fact, the body clock of people who are blind is set to a 25-hour cycle since they are unable to receive signals in the form of daylight exposure. That is why blind people often have problems with sleeping.
Why this is so is unknown, but this explains why traveling from east to west is much easier as our body's internal circadian rhythm is 25 hours, so we can adapt quickly to this time zone change.
There Is A Right Time For Everything...
Our biological clock influences how our bodies change throughout the day—our blood pressure, blood flow, blood clotting, and other processes in our bodies. Therefore, the time of the day surgery is performed or a medicine is taken may be vital to successfully treat diseases.
In fact, we have reports that cancer patients treated with chemotherapy at a proper time, which corresponds to patient's body clock of 7:00 PM, experienced considerable improvement in their health. It was also reported that diabetes patients who were given medicine at their body clock time of 7 PM were cured in just a few days.
Also, obese or overweight women who followed proper eating time according to body clock were able to lose weight.
I myself eat breakfast at 6 AM, lunch at 12 noon, and dinner at 7 PM. I don't eat anything at all after 7 PM. No work and no overtime, but just rest. It is according to my body clock, and it makes me feel fine and healthy.