Why do we tend to reach for snacks more often as daylight fades? A breakthrough study now provides concrete scientific evidence: Our internal biological clock plays a direct role in orchestrating our daily eating patterns.

In groundbreaking research at the Warren Alpert School of Medicine at Brown University, scientists studied 51 adolescents between ages 12 and 18. The participants were categorized into three groups based on their body mass index: normal weight, overweight, and obesity. These young volunteers spent 11 days in a controlled laboratory environment, completely isolated from natural light and time cues. They were offered six eating opportunities during their waking hours, with a consistent menu allowing them to eat as much as they desired at each meal.

The findings proved illuminating: Across all participants, food consumption consistently peaked during late afternoon and early evening hours, while reaching its lowest point in the morning – even in this entirely controlled environment. For teenagers maintaining a normal weight, maximum calorie intake occurred around 5:30 p.m.

The biological clock's influence on eating patterns

A notable distinction emerged between the groups: Adolescents carrying extra weight reached their peak calorie consumption nearly an hour later than their normal-weight peers. Furthermore, while the biological clock – our internal system regulating daily biological activities – influenced everyone's eating patterns, this effect showed less prominence in overweight or obese teenagers.

"This is the first study to prove that food consumption itself is regulated by our internal biological clock," Frank A.J.L. Scheer, a professor of Medicine and director of the Medical Chronobiology Program at Brigham and Women's Hospital, said.

Professor Mary Carskadon, a senior researcher at Brown, underscored the significance of these discoveries: "Adolescence is critical in shaping health patterns for life, so it's essential to understand the role of sleep processes and the biological clock in eating behavior," she said.

She suggests these insights could help physicians better guide teenagers in weight management. "For example, we can influence the timing of the biological clock by limiting exposure to light in late evening hours and increasing exposure to bright light in the morning, especially during physical activity," she explains. "This may help regulate biological rhythms and create healthy habits."

The research team emphasizes the need for further studies to determine whether influencing the biological clock's food consumption patterns leads to weight changes, whether weight changes affect how the biological clock regulates food intake, or if both factors work in tandem.

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A new study at the Weizmann Institute of Science reveals that our hormones also follow a seasonal pattern. By analyzing the data on several kinds of hormone from millions of blood tests, the researchers discovered that some hormones peak in winter or spring, and others in summer. This research, which was published in the Proceedings of the National Academy of Sciences (PNAS), USA, provides a broad, dynamic picture of hormone production – covering those connected, for example, to fertility, but also hormones such as cortisol, which are mostly short-lived and not thought to be seasonal.

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Alon Bar led the study together with Avichai Tendler; both are research students in Professor Uri Alon's group at the Institute's Molecular Cell Biology Department.

The team analyzed the hormone levels in males and females between the ages of 20 and 50, in millions of blood tests sorted according to the months of the year. The researchers tracked 11 different hormones, including cortisol (a stress hormone released by the adrenal glands), a thyroid hormone, reproduction and sex-based hormones and a growth hormone produced in the liver.

On average, all of these hormones exhibited peaks and dips over the year with a seasonal variation of around 5%, but the surprise was the ways in which certain ones peaked at different times. For example, the hormones testosterone and estradiol – one more prevalent in men, the other in women – were mirror images of one another. So the fact that more children are conceived in certain seasons may have more to do with hormone balances than the blooming of flowers in the fields, says Bar.

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Students will study at the University of Haifa's Marine Sciences school and the Interuniversity Institute for Marine Sciences in Eilat.

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The graduate student program was initiated in order to forge a connection between the next generation of oceanography professionals through international collaboration. Students are collaborating with 25 labs from six host institutions in Israel, Canada, Australia, and Sweden.

Elena Forchielli, a fourth-year Ph.D. student in molecular cellular biology and biochemistry at Boston University, is one participant who will conduct research this fall at the University of Haifa's Leon H. Charney School of Marine Sciences. She has previously visited Haifa for collaborative research with the Charney School's Daniel Sher; they will join forces again as part of her LOREX experience from Nov. 1 to Dec. 31.

"I'm excited to perform experiments at the University of Haifa that my lab doesn't have the capacity to carry out in Boston," Forchielli said. "The Eastern Mediterranean setting enables us to collect valuable samples in the sea, and then to replicate our experiments in an environment which closely resembles the conditions of the real ocean. I'm looking forward to obtaining powerful data from this process."

Given its home along Israel's coastline, the Charney School is strategically positioned to study the Mediterranean Sea in an interdisciplinary manner. The school has four complementary divisions: Department of Maritime Civilizations; Dr. Strauss Department of Marine Geosciences; Department of Marine Biology; and Hatter Department of Marine Technologies. It also offers an MBA program in shipping and ports management.

Through this exchange, the research collaboration "promises to deliver not only significant findings for the marine biology community but also the latest fruitful partnership between American and Israeli academic institutions," said Karen L. Berman, CEO of the American Society of the University of Haifa. "Situated at the doorstep of the Mediterranean Sea, the school finds itself at a cradle of maritime civilizations throughout history. There is simply no substitute for a real-world laboratory of that magnitude."

Reprinted with permission from JNS.org.

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