Summary: Circadian clocks control fat cell growth through a short daily window. For about four hours, the protein PPARG switches on, and the body decides how many fat cells to make. Stress hormones timed against that clock change metabolism. Some rhythm disruptions protected mice from fat build-up in the liver. Others promote obesity.
The new study adds to what we know about how a broken daily rhythm may lead to metabolic disorders. Some changes in the rhythm seem to protect. Others may promote metabolic disorders. So learning more about the body clock’s role could be one way to fight the pandemic of metabolic disease.
It is no secret that obesity is rising around the world. It has become a serious problem in rich nations like the US, where most people are overweight. So we need to understand it better. No doubt, one cause of obesity is eating too many calories. But we also know that two people eating similar calories do not gain the same weight. That is because metabolism differs, and many things affect it. Some push toward obesity, and others protect against it. In recent years, researchers have paid more and more attention to the body clock and the role its disruption plays in obesity. This body clock is run by the circadian rhythm. Under some conditions, changes in this rhythm may even protect against obesity. In other cases, they may promote it. The link between the body clock and obesity is complex. Understanding it is key to fighting this pandemic of obesity and related disorders. What amazed researchers is that some rhythm changes may protect, unlike what was thought before. In one study, they implanted mice with a pellet that released stress hormones all day long. This broke the rhythm. But they found this kind of stress had a protective role. More fat moved into fatty tissue. Less fat built up in organs like the liver. And the mice made more insulin. The study tried to mimic chronic stress. It lasted 21 days. Of course, that is a short time, and results may differ over the long run. Still, the study shows a complex link between the body clock, stress hormones, and obesity. It means that stress at the wrong time may have a dramatic effect on an animal’s metabolism. So the researchers ran another study to learn more. In this lab-dish study, they used a special glowing protein to track the gene that controls the daily rhythm. They used another glowing marker to watch the activity of Peroxisome Proliferator-Activated Receptor Gamma (PPARG). This protein plays a key role in making fat cells. The study made a few interesting findings. At certain times of day, PPARG levels rose, playing a key role in making fat cells. PPARG switched on only for a few hours, about four hours, each day. That is a short window. During that window, the body decides what happens to fat cells, how many to make, and much more. Fat cells build up over many days. What is interesting is that the body decides to form fat cells within a few hours each day. Researchers say they are still trying to make sense of these findings. For example, they want to know why short-term stress gives only short-lived protection. They are also looking for ways to use these findings to manage obesity and metabolic disorders. Researchers say these findings could matter a great deal. For example, people with conditions like asthma often take glucocorticosteroids (steroid drugs) every day. So researchers now need to learn whether regular steroids cause short-term or lasting changes in metabolism. We also need ways to reset or adjust the body clock. That may offer a safer, non-invasive way to fight obesity and metabolic disorders.
Frequently asked questions
How does circadian rhythm affect fat cells?
Your body clock sets a short daily window, about four hours, when the protein PPARG switches on. During that window the body decides what happens to fat cells, including how many new ones to make. Fat builds up over days. But the decision to form fat cells is made within a few hours each day. So timing matters.
What is PPARG?
PPARG stands for Peroxisome Proliferator-Activated Receptor Gamma. It is a protein that plays a key role in making fat cells. In the lab study above, researchers tracked it with a glowing marker. Its levels rose only at certain times of day, for about four hours. That short window is when the body commits to making fat cells.
Can stress hormones change how your body stores fat?
Yes, and the timing decides the effect. Some mice got pellets that released stress hormones all day for 21 days. They moved more fat into fatty tissue, stored less fat in organs such as the liver and made more insulin. Other rhythm disruptions promote obesity. It was a short study, and long-term results may differ.
Can circadian rhythms help with weight loss?
Not as a proven treatment yet. Researchers are looking for ways to reset or adjust the body clock. It may offer a safer, non-invasive way to fight obesity and metabolic disorders. The findings so far come from mice and cells studied in the lab. Scientists are still working out why short-term stress gave only short-lived protection.
Why do two people who eat the same calories gain different amounts of weight?
Eating too many calories is one cause of obesity. But two people eating similar calories do not gain the same weight. Metabolism differs, and many things shape it. Some push toward obesity and others protect against it. The body clock is one of them. Some changes in the daily rhythm seem to protect, while others promote weight gain.
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Light exposure and meal timing are among the factors reviewed in physician-led weight management.
Dr. Gurpreet Singh Padda, MD, MBA, MHP
