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. This also applies across generations, according to a recent study. Thus cold leads to more brown adipose tissue in offspring and protects it against obesity and metabolic diseases, reports the Swiss Federal Institute of Technology Zurich (ETHZ) on the study results. Information carriers are the sperm.

In mice, the scientists of the ETHZ could prove that the outside temperature at the time of conception has far-reaching influence on the offspring. An international team of researchers headed by ETH Zurich Professor Christian Wolfrum was able to demonstrate that a central course is set even before conception. If the father stays in the cold before being conceived, the offspring will have more active brown adipose tissue. In other words, an environmental impact to which the father is exposed is transferred to his offspring, the researchers report. A similar relationship is also evident in humans.

The outside temperatures at the time of conception have a significant impact on the child's health. (Image: tcsaba / fotolia.com)

Brown adipose tissue with many advantages

If you have a lot of brown adipose tissue, you can be lucky: this tissue that occurs in some people below the tongue, in the area of ​​the clavicle and the spine helps in the utilization of excess energy, explain the study authors. The more one has 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 in investigations on mice.

Creation time with far-reaching influence

A relationship between the temperature at conception and brown fat shows, according to the researchers also in humans. The researchers analyzed computed tomography images of 8,400 adult patients and found that people who had a birthday from July to November (and were thus conceived during the winter months) had significantly more active brown adipose tissue than those born January to June (and Time of preparation in the summer half-year).

Outside temperatures affecting the fathers

In the mice studies, the animals were either kept at moderate (23 degrees Celsius) or cool (8 degrees Celsius) temperatures and could reproduce naturally. "The analyzes of 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. Their study results have been published in the journal "Nature Medicine".

Protection against obesity and metabolic diseases

Offspring of males that remained in cool environment for several days before conception had more active brown adipose tissue than males living in temperate temperatures, the researchers explain. Also, the offspring of males who were in the cold, better from overweight (with high fat diet less weight gain) and were protected against metabolic diseases.

Epigenetic changes in the sperm

According to the ETH Zurich, the researchers were able to use in vitro fertilization and sperm analysis to show that the information on the father's residence temperature is passed on to the offspring via epigenetic imprinting of the sperm. This is a change of the pattern, which form certain chemical marks (methylations) on the genetic material. It has long been known that environmental influences can alter the epigenetic pattern of sperm. For the first time, however, the scientists were able to prove that the ambient temperature also leads to epigenetic changes, reports the ETHZ.

Better protection against cold

With regard to the function of the brown fat cells, the experts explain that the focus here is primarily on the generation of body heat through the burning of energy. Thus, mice with more brown adipose tissue are able to better regulate their body temperature at low temperatures. According to Professor Christian Wolfrum, they may "possibly be protected from freezing cold, which may explain why this epigenetic mechanism prevailed in evolutionary history." In addition, findings in mice and humans are in line with earlier observations that humans in cold regions are particularly affected have a lot of brown fat, the researchers say.

Effects of temperatures in our living environment

The authors of the study make another connection clear. There are already studies that show a relationship between living temperature and obesity. In addition, the average indoor temperature has increased in recent decades, at least in the US. This could possibly also have effects on body fat and the risk of metabolic diseases. To what extent, for example, couples who deal with family planning, should focus on cold, remains open.

Help cool down before procreation?

According to the researchers, it would probably not help if the man deliberately cools down before the act (for example, by swimming in the cold lake). "Before we can give such advice, we need to better understand the context in humans," emphasizes Prof. Wolfrum. Probably for a epigenetic imprint but a longer exposure to cold is necessary. According to the study leader, "jumping into the cold water or resting on a block of ice may not be enough." Other studies comparing the epigenetic character of human sperm in summer and winter are already in the pipeline, according to the researchers , (fp, pm)