Jonatan Ruiz
Professor in the Department of Physical Education and Sport at the Faculty of Sports Sciences, Director of the Joint University Institute for Sport and Health (iMUDS) at the University of Granada, and Coordinator of the CIBEROBN Group on Physical Activity and Obesity
Is the study of good quality?
“This is an extremely robust study analysing more than 4,000 population-based studies using measured — rather than self-reported — height and weight data from over 230 million people across 200 countries between 1980 and 2024. Its main strength is that it does not simply examine ‘how much obesity there is’, but also the speed at which obesity rates are increasing, stabilising or declining.”
Are there any limitations that should be taken into account?
“The main limitation is that, as this is a global analysis, some countries have less available data and the estimates therefore rely on statistical modelling. In addition, the study describes trends, but it cannot establish with certainty which policies, social changes or cultural factors may explain the stabilisation or decline in obesity.”
What are the implications of the study, and how does it fit with the existing evidence?
“In my view, the most important message is that obesity is not progressing uniformly across the world: in many high-income countries it appears to have slowed or stabilised, whereas in low- and middle-income countries it continues to accelerate. This fits with the concept of an ‘obesity transition’: obesity initially rises with the modernisation of food systems and lifestyles, and may later stabilise if social norms, diet, education, public policies or access to healthier environments improve.”
What is happening in Spain, and what might explain it?
“Spain is among the few countries where, in adults, the trend has not only levelled off but may even be showing a slight reversal, in both women and men. This is likely not due to a single factor, but rather to a combination of influences, including partial preservation of the Mediterranean diet, greater nutritional awareness, more physically active lifestyles, healthier living patterns, increased health awareness, and possible generational changes. Nevertheless, the study itself makes clear that, with the available data, direct causality cannot be established.”