Indulging in snacks rich in saturated fats during winter can mislead your body into accumulating more fat, as noted by recent findings.

Researchers at the University of California, San Francisco (UCSF) have uncovered that the types of dietary fat we consume can affect how our bodies recognize seasonal changes.

“Our research indicates that the food you eat plays a crucial role in informing your body clock about the time of year,” stated Dr. Dan Levin, a postdoctoral fellow in neurology at UCSF, in a conversation with BBC Science Focus.

They discovered that consuming more saturated fat—found in red meat, butter, cakes, pies, and various baked goods—activates a protein named PER2, signaling your body that it’s summer and that it needs to store energy for the forthcoming colder months.

Conversely, consuming unsaturated fats (present in nuts, seeds, fatty fish, and vegetable oils) influences PER2 to make your body believe it’s winter, prompting it to utilize the energy from food.

These conclusions arose from experiments where the UCSF researchers simulated seasonal transitions by altering light and dark periods for mice.

During the experiments that mimicked spring and fall, mice were exposed to 12 hours of light daily, 20 hours during summer, and only 4 hours in winter.

As the faux winter nights extended, the mice, on a balanced diet, exhibited normal nocturnal behaviors, such as running on wheels as darkness fell.

However, the mice on a high-fat diet took longer to wake up and began their running routine much later after the artificial sunset, indicating a misalignment of their internal clock with the simulated light conditions.

The scientists then assessed the impacts of various dietary fats. Mice consuming a diet abundant in saturated fat were found to wake up several hours later than their counterparts before engaging in physical activity.

As a result, increased saturated fat consumption during these simulated winter conditions appeared to further disrupt the synchronization of the body’s internal clock with the light cycles.

Professor Levin emphasized that, despite being conducted on mice, the relationship between dietary fats and the body clock via the protein PER2 is likely relevant across different species.

“We believe that many insights gained from our mouse studies can be translated to humans,” he remarked. “I am eager to discover any disparities that may exist between species.”

How Our Bodies Prepare for Winter

For both wild animals and hunter-gatherers, adapting to seasonal changes is vital for survival, especially during prolonged, harsh winters when food is limited.

“In nature, fluctuations in water availability, light, and temperature dramatically alter the environment each season, compelling all organisms within the food chain to adjust,” noted Levine.

“For instance, one adaptation is for plants to produce more unsaturated fats, aiding their survival in cold, which causes both herbivores and carnivores to consume and store greater amounts of unsaturated fats.”

Thus, our bodies might be biologically programmed to anticipate higher intake of unsaturated fats as daylight hours shorten.

However, because we have access to the same food options throughout the year, many individuals often disregard this natural dietary shift.

We can indulge in our favorite saturated fat-laden foods year-round, but excessive consumption in the fall or winter can mislead your body clock into thinking it’s still summer.

“In modern society, foods high in saturated fats are abundantly available,” asserted lead author Professor Louis Ptacek, a UCSF neurologist, in BBC Science Focus. “Moreover, we often eat at ‘unnatural’ times due to light conditions. Generally, adhering to a consistent circadian eating schedule during daylight is healthier.”

Levin added that consuming seasonally appropriate foods might also be advantageous, suggesting a potential shift in fat sources throughout the year. However, he stated that further research is needed to validate this strategy.

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