Our body weight does not only depend on how we feed and how much we move. Genetic influences also play a role – and even the temperature at which we were converted. This is suggested by a study that has related the season of their conception in almost 700 people to the activity of the brown adipose tissue. Anyone who was converted in the winter half-year tends to have a more active brown adipose tissue, which is associated with higher energy consumption and a lower body mass index. The effect could be based on the fact that cooler outside temperatures influence the epigenom of fatherly sperm.
Most of the fat reserves of adults consist of white adipose tissue, which acts as a long -term energy storage – and is sometimes difficult to get rid of. Brown fat tissue, on the other hand, can convert the stored calories directly into heat. It is particularly active in infants. But even in adults, the brown adipose tissue can be activated by cold. The more active the brown adipose tissue, the less energy is saved in the form of white adipose tissue. People with particularly active brown adipose tissue are therefore average slimmer. So far, little has been researched which factors contribute to individual differences.
Active brown adipose tissue in winter-produced
A team led by Takeshi Yoneshiro from the University of Tokyo in Japan has now examined the influence of the season and their typical temperatures in the care. In addition, the density and activity of the brown adipose tissue in 356 young men from Japan. Since the brown adipose tissue is mainly activated by cool temperatures, the test subjects stayed in a room air -conditioned to 19 degrees Celsius before the measurement. For the evaluation, the researchers compared in the cold half of the year, i.e. between October 17th and April 15, had been compared with those who had been organized in the warm half of the year between April 16 and October 16.
The result: “An active brown adipose tissue seemed significantly more common in people who were generated in the cold season,” reports the research team. While only 66 percent of individuals had an active brown adipose tissue in the summer generation group, the winter generation group was 78 percent. In order to further support the results, Yoneshiro and his colleagues examined over 300 other men and women between the ages of three and 78. This cohort also showed that the brown adipose tissue was particularly active in people who were generated in the cold season.
Does the sperm program
A comparison with historical weather data for the respective production time revealed that apparently large daily temperature fluctuations and a low outside temperature in the production are associated with a more active brown adulthood in adulthood. “However, other parameters, such as the length of the day, duration of the sun, humidity and precipitation shortly before the conception, were not related to the activity of the brown adipose tissue,” report the researchers. They were also unable to demonstrate any influence for the weather conditions in other phases of pregnancy or after birth.
Although the underlying mechanisms are still unclear, according to Yoneshiro and his team, these results indicate that it is not the mothers, but the fathers are decisive for the effect of temperature on the offspring. This interpretation also fits an earlier study of mice, in which a cold exposure of the males – but not the female – before the generation, led to the brown adipose tissue more active in the offspring. The reason for the effect could be cold -related epigenetic changes in sperm. This effect could have been evolutionary: Anyone who can create heat with their brown adipose tissue is better equipped for cold ambient temperatures.
According to Raffaele Tepperino from the Helmholtz Zentrum Munich, which was not involved in the study, these results are relevant in view of the increasing global warming. “The new findings once again underline the crucial role of the environmental conditions at the time of the generation of the formation of the metabolism of the descendants,” he writes in an accompanying comment, which was also published in the Nature Metabolism journal. “This means that they offer perspectives for understanding the coexistence of two global health problems – obesity and global warming – and their coping with tailor -made strategies to influence the lifestyle.”
Source: Takeshi Yoneshiro (University of Tokyo, Japan) et al., Nature Metabolism, DOI: 10.1038/S42255-025-01249-2