season

It turns out your body’s metabolism might have been influenced long before you were even born, specifically, by the season your parents conceived you. A study from the University of Tokyo found a fascinating link between conception in colder months and a potentially faster metabolism in adulthood.

Researchers looked at 642 Japanese adults and calculated when they were likely conceived. They discovered that people conceived during winter tended to have more active brown fat as adults. Brown fat is a special kind of fat that burns energy to produce heat and helps regulate blood sugar levels—even when you’re at rest. The result? A higher resting energy expenditure and possibly a lower risk of obesity.

Lead researcher Dr. Takeshi Yoneshiro believes that cold exposure around the time of conception may cause epigenetic changes—alterations in how genes are expressed—which can lead to more brown fat later in life.

Professor Jaswinder Sethi, an expert in metabolism at the University of Southampton, added that brown fat plays a major role in keeping us warm and contributes to the number of calories we burn, which may help prevent weight gain and metabolic diseases.

However, not everyone is convinced it’s a major factor. Dr. Adam Collins from the University of Surrey pointed out that while brown fat may boost cold tolerance, it may not significantly raise the metabolic rate for most people.

Bottom line? This study is observational—it shows a pattern but doesn’t prove cause and effect. Still, it’s a fascinating peek into how something as subtle as seasonal temperature might influence long-term health. And who knows? It might one day inspire new ways to support healthy metabolism from the very beginning of life.