Why does weight increase – in children, adolescents, and adults?

Global projections of weight trends, new mathematical models, and critical perspectives on common explanations.

We covered a lot of ground, and the reading level was high when a group of the world’s leading researchers on the causes of obesity visited Copenhagen for our full-day symposium, Symposium on the Obesity Epidemic – Understanding the History, Drivers, and Future of the Obesity Epidemic in Children and Adolescents.

External input

The day included presentations and group discussions, where graphs, methods, hypotheses, numbers, and perspectives were examined and debated.

Nina Geiker, Research Director at the Centre for Childhood Health, explains why it is important to organize a symposium like this:

“Curiosity is one of the center’s core values. We need to be open to new explanations and connections. We need to test our hypotheses and look at methods and models without bias. One way we do this is by bringing in external input and debating it.”

It was also an opportunity to invite Danish researchers, practitioners, and students to hear from some of the top international experts in the field. The symposium was open to all and had around 160 participants.

A scientific marketplace

The center aims to be a meeting place for exchanging ideas and knowledge that can advance the collective understanding of what affects children’s and adolescents’ weight.

Stanley Ulijaszek from Oxford University also argued in his presentation that more bridges should be built between scientific disciplines so that information and knowledge can be exchanged like in a marketplace.

“You don’t need to share underlying analyses and theoretical frameworks to collaborate. You take what you can use and move on,” he said, advocating for more interdisciplinary cooperation.

The trend started before fast food

Professor Emeritus Thorkild I.A. Sørensen – strategic advisor to the center and the main architect behind the symposium – has studied the mysteries of weight for decades. As early as the 1970s, he documented that the rise in population weight began in the 1940s.

“That was long before fast food and television became part of everyday life, which are often cited as explanations. So it was a mystery – and it still is,” he says.

Multiple explanations at once?

George Davey Smith from the University of Bristol and David B. Allison from Indiana University School of Public Health encouraged looking for causes in completely new places. Many explanations – such as fast food – keep resurfacing in the debate despite lacking evidence.

“It’s almost like a zombie in a horror movie that refuses to die,” as George Davey Smith put it.

Perhaps it’s time to accept that weight trends may result from many small, simultaneous factors, suggested David B. Allison, who offered several possibilities:

“For example, we get fewer infections thanks to better treatments and vaccines. We also have fewer parasites in our bodies than before. We can also see that the average body temperature is decreasing in many places, without knowing why. The same goes for testosterone levels.”

These are small changes that may be connected, may reinforce each other, and may affect weight, he explained.

“And maybe weight is the price we pay for an overall healthier population?”

Using what works

At the Centre for Childhood Health, we are now continuing this work – across disciplines and approaches – like in a marketplace, where ideas are exchanged, and we use what works.