The described studies explore differences in overweight and obesity in the adult, child, and youth populations in Spain, using data from the ENE-COVID seroprevalence study, thus having a large study sample. The main contribution of both studies is their representativeness at the provincial level, allowing them to explore territorial differences in the prevalence of excess weight. Both studies show that populations with lower socioeconomic status, both individual and contextual, have higher rates of overweight and obesity, consistent with previously published studies with different populations, including those conducted in Spain.

Both studies have a large population sample and employ correct analyses to address the stated objectives. However, there are two aspects that need to be highlighted: firstly, the study sample was designed to study the prevalence of SARS-CoV-2 infection in the Spanish population and not the prevalence of obesity or other associated diseases. This affects the sampling design, which, for example, includes stratification levels that take into account population density in response to the original needs of the sample (due to its connection with virus transmission), which might not be considered for a study of this nature.

Secondly, the Body Mass Index (BMI) is used as an indicator of overweight and obesity. On one hand, it is an increasingly contested measure in the scientific community as a valid health indicator, due to various elements such as not measuring the percentage of body fat or using universal classification standards that do not account for demographic differences. Moreover, the present study does not collect anthropometric measurements standardized for deriving BMI (weight and height) but relies on self-reported data provided by the participants in the interview. Evidence suggests that when BMI is identified from self-reported measurements, it tends to overestimate BMI values in underweight patients and underestimate values in those with higher weight, which may introduce biases in the measurements used in both studies.

The two studies show very concerning results both in the child and adult populations due to extremely high prevalences of overweight and obesity.

Once again, there are geographical (between regions) and social (between social classes) inequalities, which we refer to in public health as 'the social gradient of disease.'

This is an analysis of data from an ENE-COVID study that was not designed to study adult and child obesity, but it does corroborate previous data and knowledge.

In terms of childhood overweight and obesity, Spain, along with Greece and Italy, presents the most concerning data in all of Europe, with overweight and obesity prevalences close to 40%, while in countries like Denmark or the Czech Republic, prevalences are exactly half that.

Therefore, from a public health perspective, in terms of health protection and prevention of diseases associated with overweight/obesity, this is an enormous and concerning challenge in Spain, and it is an uneven challenge. A challenge that, from the perspective of childhood, in Spain involves developing and implementing the national plan to reduce childhood obesity effectively.

Obesity is a complex problem, globally present, that we must take very seriously in Spain and in Europe, where there are already successful experiences.