The role of the biological clock (circadian rhythm) on human health and disease was covered in depth at the 2023 American Physiology Summit. Learning about how the body’s clock works with other organs is a topic scientists are continually intrigued by.

At the 2024 Summit, Satchin Panda, PhD, from the Salk Institute for Biological Studies, provided important insight on how circadian rhythms regulate liver function and made a compelling case for time-restricted eating according to your natural sleep cycle.

Eating only within a specific window of less than 12 hours per day is most often referred to in the media as “intermittent fasting.” This way of eating changes gene expression in the liver of mice, which causes weight loss and alleviates several metabolic conditions. In this study, sugar and fat metabolism, heart health and overall liver function improved in mice compared to mice fed the same number of calories that were not on the time-restricted schedule.

Karen Gamble, PhD, from the University of Alabama at Birmingham, also supported the benefits of time-restricted eating in her talk by addressing its effect on kidney function. Her research found that time-restricted eating alleviates chronic kidney disease symptoms by making the kidneys filter out toxins more efficiently, restoring blood flow to the kidneys and reducing the formation of scar tissue. Gamble pointed out that nighttime shift workers already have a higher chance of developing cardiometabolic conditions because their circadian rhythms don’t align with their eating schedule. When you combine that with a high-salt diet, the body’s ability to regulate its sodium-water balance decreases drastically. This can cause high blood pressure and kidney disease.

Understanding how misalignment of the circadian clock contributes to disease lets us appreciate its role in aging. Karyn Esser, PhD, from the University of Florida, provided fascinating insights on how the skeletal muscle’s clock works. Her work answers an age-old question: Is there is a perfect time in the day to exercise?

Apparently, your skeletal muscles will thank you if you work out in the afternoon, especially if you have Type 2 diabetes. Esser’s research has shown that people with Type 2 diabetes who exercised between 3 and 6 p.m. had more improvement in their glucose metabolism than when they worked out at other times of day.

This finding is not surprising because your cortisol (a stress hormone) levels are highest in the morning after you wake up and decline throughout the day. Cortisol increases blood glucose levels, so exercising early in the morning while your body cortisol levels are high already may not be an ideal strategy for managing your blood sugar. 

This Summit session reported on very important findings that can be boiled down to some good life advice: Adhere to a consistent sleep schedule and exercise and eat meals at specific times of day. This may be a challenge in your busy life, but the benefits of being meticulous about your day-to-day schedule may help you stay healthy in the long run.