Focus on environments and systems to tackle childhood overweight and obesity

IHME and collaborators have published two new studies in The Lancet that examine overweight and obesity worldwide in children and adolescents (available at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(25)00397-6/fulltext) and adults (available at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(25)00355-1/fulltext) since 1990 with forecasts through 2050. IHME interviewed Dr. Jessica Kerr, an adolescent health researcher at the Murdoch Children’s Research Institute and the lead author of the study focused on children and adolescents.

Katherine Leach-Kemon: In your study, you note that among children and adolescents globally, there’s been a doubling of the prevalence of overweight and obesity, and a tripling of the prevalence of obesity between 1990 and 2021. What is driving this?

Dr. Jessica Kerr: The drivers of the obesity epidemic are complex. For example, there are interacting factors between one’s genetic biology, developmental things going on, obviously with children, adolescents, and the environment. We tend to think about it as a biological response to living in an obesity-promoting environment. It’s difficult to maintain a healthy lifestyle when they're living in an environment where they are surrounded by ultra processed foods that are affordable and good. Some people are more affected by living in these environments than others, and quite often these environments promote weight gain. I guess another way to think about it is, how did the environment become so obesity-promoting? We see that these obesogenic environments arise from fast paced changes such as urbanization and economic development and changes in food systems that all encourage high growth and consumption. That is how things start. And once you’re living in the environment, it can be difficult to break that cycle.

Katherine Leach-Kemon: Definitely. Some researchers have stated that obesity is plateauing among children and adolescents. Your work, however, paints a vastly different picture, noting that you don’t expect obesity to stabilize in any region before 2050. Why is that?

Dr. Jessica Kerr: That’s a good question. Our results do look a bit different from other studies. We didn’t see obesity prevalence by itself plateauing or decreasing in any region or country before 2050. I think what’s important to note that, in our paper, we separated overweight from obesity because we saw these as two different health states. Overweight is more of a risk marker for what problems might come in the future – kind of pre-obesity – whereas obesity is more of a marker for disease. We decided to separate these and see what was going on with each of them. What we saw was that the trajectory of overweight prevalence was stabilizing and even decreasing in some regions of the world, and obesity was increasing. We think that what’s happening is that when studies report overweight and obesity together, it can mask those findings.

Katherine Leach-Kemon: In the study, you note that you anticipate that the greatest increases in obesity will occur in the future. Can you tell me more about this?

Dr. Jessica Kerr: The greatest increases that we saw in obesity prevalence in the paper were happening in the future period through 2050 compared to the past period. This is an important finding because it means that we have a great opportunity to impact this public health crisis if we act now with multi-sectorial actions coordinated across government at the system level. I think it’s important that we don’t think it is too late, because that’s not what the data are showing us. And we did find there were some populations living with more obesity than overweight. But we also saw quite a lot of regions and countries that are still forecast to be living with more overweight than obesity even until 2050. These are real opportunities for prevention, and that’s occurring in parts of South Asia, Central Asia, and Europe.

Katherine Leach-Kemon: What steps do you think decision-makers should take right now to slow or reverse these trends?

Dr. Jessica Kerr: It’s important to realize that we need to change our overarching systems rather than our people. Our environments need to change. We need coordinated action across the entire life course, not just in a little period of childhood and not just in a period of adulthood. We found that adolescence was an important time period in our study because people tend to gain weight and experience a lot of developmental shifts between 15 to 24 years old. And we also know it’s an important period where our adolescents are entering their reproductive years.

Secondly, we need coordinated action across multiple layers of the problem and of government. Too often, we focus just on the young person and what we can do to change this one young person. But we need to move away from these kinds of individual level strategies that tend to blame the person or the family. And we need more of a systems-level approach from government, including changing big things that are going to affect more people. That includes trying to shift the commercial determinants, such as taxing sugar-sweetened beverages or regulating unhealthy food and food advertising to children and subsidizing healthy food options. In lower-middle-income countries, that means supporting local farming and agricultural practices before they are overtaken by big food companies.

Katherine Leach-Kemon: You’re stressing the urgency of addressing overweight among children and adolescents before it progresses to obesity. What does that look like?

Dr. Jessica Kerr: There are a lot of regions that we forecast are going to have countries. It's still important to remember that we need to help support their systems and stop their systems being overtaken and becoming obesity-promoting.

Katherine Leach-Kemon: Are there promising interventions you can point to in specific countries and regions?

Dr. Jessica Kerr: A nice example that I always give is the Amsterdam Healthy Weight Approach. It used a systems-level approach. They didn’t just focus on schools and families. They went to the whole community and to the health sectors. They had government involved. It was a citywide effort. They made changes to recreational facilities and sports participation. And, for example, they tried to change the types of foods that were eaten at sports games, and that type of thing requires people to come on board and support you from both the public and private sector. They tried to go across the whole city and change multiple policies to focus on reducing obesity, not just health policies, and they had some nice results. Although these interventions only change body mass index by a little bit, they actually make a difference at the population level.

We also found an intervention that was implemented in schools in China. It is called the Decide Children intervention. It was a school-based intervention. They focused on children and changing education around physical activity and nutrition, but they also tried to change the school environment. They engaged families, community leaders, and local stakeholders to try and make this more of a system level intervention. They changed things such as policies at school. There were no sugar-sweetened beverages allowed, and they encouraged different things like sports participation and things like that.

Katherine Leach-Kemon: You note that Australia and the US are unique in the speed at which obesity took hold among children and adolescents. Why did this occur so early in these countries compared to others?

Dr. Jessica Kerr: It was an interesting finding that Australasia and North America were the first groups in the world to transition to more obesity than overweight, and that happened especially quickly for children and adolescent girls in Australasia and for adolescent girls in North America. This means there were more girls with obesity than with overweight in those countries, and that was by 2010. In terms of why this happened, they are two high-income regions where the drivers for obesity changed a long time ago. Their food systems have long been overtaken by big food companies. They’ve had more time in these obesity-promoting environments. They started their nutrition transition to Western style diets a long time ago. Girls were particularly affected in these regions probably due to an interaction between different developmental, social, and biological drivers, including things like hormones and puberty and different opportunities for exercise. These trends are particularly concerning given that they’re females, they’re about to enter their childbearing years, and we know that obesity can be transmitted intergenerationally to the next generation of offspring and children.

Katherine Leach-Kemon: My last question is, given that you’re in Australia, what do you hope decision-makers in your country will do differently because of your findings?

Dr. Jessica Kerr: In Australia, obesity often seems too big and too complex and too hard to tackle, especially because it doesn’t belong to any one part of government. It spans multiple portfolios. It gets lost in the system, and no one seems to take full responsibility for it. What we would hope to come from this paper is a clear message that we need strong leadership in this space across all levels of government, we need multi-sectorial action. We need people to take responsibility in health and education and transport. Also, we’d love it if people stopped focusing on the individual level – the eat less, move more ethos – and blaming families and parents. Rather, it’s the overarching systems that we want people to recognize need to change rather than focusing on blaming and trying to get individual people to change.