According to researchers from the Helmholtz Centre for Environmental Research (UFZ) in Germany, plasticizers contribute to weight gain. The scientists claim to have found the metabolic pathways that are responsible.

Plasticizers such as phthalates occur in some types of soft plastics, such as PVC. They enter the body through the skin or are ingested with certain foods. Some phthalates behave as endocrine disruptors and are suspected of having an influence on our body weight. The exact correlations and mechanisms have been unclear thus far.

Now, in collaboration with the Integrated Research and Treatment Center (IFB) Adiposity Diseases at the University of Leipzig and Leipzig University Hospital, the UFZ researchers have published an unsettling study in PLOS ONE, a peer-reviewed multidisciplinary Open Access journal that offers a platform to publish primary research. The study not only shows that the phthalate DEHP leads to weight gain, but also reveals the metabolic processes involved. In Europe, DEHP was added to the list of restricted substances in 2015.

In Germany, one in two adults is overweight, as are up to 15% of German children and young people. "The figures are alarming," said Martin von Bergen, Head of the Department of Molecular Systems Biology at the UFZ. "Because every kilo over the ideal weight increases the medical risk of cardiovascular disease, joint damage, chronic inflammation and cancer and the number of overweight people is constantly increasing all over the world."

While genetics, poor dietary habits and a lack of exercise are all seen as contributing factors, it would now seem that certain environmental pollutants, such as phthalates, may also be partly responsible for the obesity epidemic.

"Correlations between increased phthalate concentrations in the human body and the development of overweight have already been proven in epidemiological studies and should be analyzed in more detail," von Bergen said.

Phthalates are used as plasticizers in polymer processing to make plastics soft, flexible or tensile. Under certain conditions, phthalates can also leach from the material and enter the body, generally from a dietary source. Phthalates are mainly transferred from the food packaging of fatty products, such as cheese or sausage.

"We currently know very little about how exactly phthalates have an effect within the body and how they can influence body weight—we intended to evaluate this in our study," Von Bergen added.

The study reveals where phthalates can interfere with metabolism and thus pave the way for weight gain. In studies at the University of Leipzig, mice exposed to the phthalate DEHP in their drinking water gained a substantial amount of weight—especially the females.

"It is evident that phthalates seriously interfere with the hormone balance. They give rise to significant changes, for example weight gain, even in low concentrations," said von Bergen.


The work at the UFZ focused on defining the metabolic products in the mice's blood. The researchers determined that phthalates caused the proportion of unsaturated fatty acids in the blood to rise. Disrupted glucose metabolism was another effect. The composition of receptors in the blood also changed. These receptors are important for general metabolism and may cause it to change.

 "Some metabolic products that are formed by adipose tissue also act as messengers and control functions in other organs," explained von Bergen. "However, there is no conclusive clarification of how the various effects of phthalates on metabolism influence each other and ultimately lead to weight gain."

Von Bergen will continue to research the influence of phthalates on metabolism in collaboration with his colleagues from the University of Leipzig and the University Hospital Leipzig. He is also studying the impact of phthalates on the development of early childhood diseases with UFZ colleagues from the Department of Environmental Immunology within the framework of the mother-child study (LiNA).

"Our aim is to conduct solid basic research so that our results can then help the authorities responsible for assessing the risk of chemicals in Germany and at European level to perform their evaluations," said von Bergen.