The amount of fat we eat can signal the season to our bodies. A new study from a UCSF team found that meals high in saturated fat can trick the body’s internal clock. That confusion can lead to increased fat storage and weight gain.
The study suggests the amount of fat in our diet affects how our bodies respond to seasonal changes.
What Did the Scientists Discover?
“The types of food you consume help your body determine the season,” neurologist Dan Levin, the lead author of the study, told BBC Science Focus in an interview.
His team found that eating more saturated fats — found in red meat, butter, cakes, pies, and other buttery pastries — causes the protein PER2, which regulates circadian rhythms, to signal the body that it’s summer. That signal prompts the body to store more energy as if preparing for the cold winter months.
However, if we eat more unsaturated fats — those found in nuts, seeds, fatty fish, and plant oils — PER2 makes the body believe that winter has already arrived, signaling that the body needs to burn the energy it consumes.
At least, that outcome came from a non-invasive experiment on mice. The team exposed the rodents to cycles of light and darkness to simulate seasonal changes. To mimic spring and autumn, the mice received 12 hours of light per day; for summer, 20 hours; and for winter, just 4 hours of light.
As the nights grew longer in the artificial winter, mice fed a balanced diet showed typical winter behavior for nocturnal rodents. They began running on wheels as soon as it got dark.
Meanwhile, mice fed high-fat diets took longer to wake up. They started running significantly later than the artificial sunset, indicating their internal clocks were out of sync with the light cycles.
The researchers then compared the effects of different types of dietary fats. They found that mice consuming a diet high in saturated fats woke and began running on wheels only many hours after midnight. Thus, their internal clocks became increasingly desynchronized from the light schedule as they consumed more saturated fats during the artificial winter.
Dr. Levin said that most of the findings from the rodent study are relevant to humans.
“In the wild, seasonal changes in water, light, and temperature completely alter the landscape and force organisms throughout the food chain to adapt. One such adaptation is for plants to produce more unsaturated fats to survive the cold. This compels herbivores and carnivores to consume and store more of these types of fats,” Dr. Levin remarked.
Therefore, our bodies are programmed to seek out more unsaturated fats as the days grow shorter. However, many people lose this natural seasonal shift in diet because they have access to the same foods year-round.
We can indulge in our favorite high-saturated-fat foods regardless of the season, forgetting that excessive consumption in the fall and winter can desynchronize our biological clocks. The team emphasized that eating on a schedule aligned with our daily circadian rhythms is generally healthier.
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