What effect does the outside temperature have on our body weight?

Cold prevents overweight and metabolic diseases in offspring

The temperatures in our environment have a significant impact on our metabolism and the risk of certain diseases. According to a current study, this also applies to all generations. For example, cold before conception gives offspring more brown adipose tissue and protects them against obesity and metabolic diseases, the Swiss Federal Institute of Technology Zurich (ETHZ) reports on the study results. The sperm are the transmitters of information.

The scientists at the ETHZ were able to demonstrate in mice that the outside temperature had a far-reaching influence on the offspring during conception. An international team of researchers headed by ETH Professor Christian Wolfrum was able to demonstrate that a key course is set prior to conception. If the father stays in the cold before conception, the offspring have more active brown adipose tissue. In other words, the environmental impact that the father is exposed to is transferred to his offspring, the researchers report. A similar connection can also be seen in humans.

Brown adipose tissue with many advantages

Those who have a lot of brown adipose tissue can count themselves lucky: This tissue, which occurs in some people below the tongue, in the area of ​​the clavicle and spine, helps to utilize excess energy, the study authors explain. The more you have of the tissue and the more active it is, the lower the risk for a person to become overweight or to develop metabolic diseases. The research team came to this conclusion when examining mice.

Date of conception with far-reaching influence

A connection between the temperature at conception and brown fat can also be seen in humans, according to the researchers. The scientists had analyzed computed tomography images of 8,400 adult patients and were able to show that people who were born in July to November (and were therefore born in the winter half-year) have significantly more active brown adipose tissue than people who were born in January to June (and Generation in the summer half year).

Outside temperatures affecting fathers

In the studies of the mice, the animals were kept either at moderate (23 degrees Celsius) or cool temperatures (8 degrees Celsius) and were able to reproduce naturally. "The analyzes in the offspring showed that the mother's temperature before and after conception had no influence on the brown adipose tissue in the offspring, but that of the fathers"; the scientists report. They published their study results in the journal "Nature Medicine".

Protection against obesity and metabolic diseases

The offspring of males who stayed in a cool environment for a few days before conception had more active brown adipose tissue than those of males who stayed at moderate temperatures, the researchers explain. The offspring of males who stayed in the cold were better protected from being overweight (less weight gain with a high-fat diet) and from metabolic diseases.

Epigenetic changes in the sperm

According to information from the ETHZ, the researchers were finally able to use in vitro fertilization and tests on sperm to show that information about the father's temperature at home is passed on to the offspring via an epigenetic character of the sperm. This is a change in the pattern that certain chemical markings (methylations) form on the genetic material. It has long been known that environmental influences can change the epigenetic pattern of sperm. For the first time, however, the scientists have been able to demonstrate that the ambient temperature also leads to epigenetic changes, reports the ETHZ.

Better protection from the cold

The experts explain the function of the brown fat cells that the main focus here is the generation of body heat by burning energy. Mice with more brown adipose tissue are able to regulate their body temperature better at low temperatures. According to Professor Christian Wolfrum, this could "possibly protect them from freezing cold, which could explain why this epigenetic mechanism has become established in the history of evolution." In addition, findings in mice and humans are in line with previous observations that humans in cold regions are particularly strong have a lot of brown fat, the researchers say.

Effects of the temperatures in our living environment

The study authors make another connection clear. There are already studies that show a connection between living temperature and being overweight. In addition, the average temperature indoors has increased in recent decades, at least in the United States. This could potentially affect body fat and the risk of metabolic disorders. To what extent, for example, couples who deal with family planning should now specifically focus on cold, remains open.

Help cool down before conception?

According to the researchers, it would probably not help if the man cooled off specifically before the act (for example, by swimming in the cold lake). "Before we can give such advice, we have to better examine the connection in humans," emphasizes Prof. Wolfrum. Longer exposure to cold is probably necessary for epigenetic imprinting. According to the study director, “a dip in the cool water or a short rest on a block of ice may not be enough.” According to the researchers, further studies in which the epigenetic characteristics of human sperm are to be compared in summer and winter are already being planned . (fp, pm)

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