This article examines childhood obesity and its negative impact on physical fitness levels. The World Health Organisation (WHO) defines obesity, a complex disease, as ‘abnormal or excessive fat accumulation that presents a risk to health’. The latest WHO report, published in 2022, found that 390 million children and adolescents aged 5 to 19 were overweight, while 160 million of them were obese.

Body mass index (BMI) is the commonly used indicator worldwide in epidemiological and public health studies to assess and monitor the nutritional status of populations. BMI is a simple ratio of weight (expressed in kg) to height (expressed in m2). It is now generally accepted that overweight (BMI value) in the adult population is between 25 and 29.99 kg/m2 and obesity (BMI value ≥30 kg/m2). The values in children that define these weight categories are different, because they have to be adjusted for age and gender according to the WHO’s proposed growth standards for children (we recommend visiting the following website for more information: https://www.who.int/tools/growth-reference-data-for-5to19-years/indicators/bmi-for-age). 

One of the key questions asked by researchers is as follows: what, if anything, causes obesity? Available research across the years shows that it involves a combination of factors, including individual characteristics (e.g. genetic and hormonal factors, lifestyle habits, mental health aspects, etc.) and the environment (e.g. access to primary health care, access to recreational and leisure facilities, access to unhealthy foods, education, obesogenic environments, etc.). A related question is as follows: do people with obesity have an increased risk of developing other diseases? The answer is yes. There is now scientific evidence showing that obesity tends to trigger the onset of other chronic diseases, such as diabetes, cardiovascular disease and some types of cancer. People with obesity also tend to have their physical and mental well-being seriously compromised.

But there is good news despite this scenario: obesity in most cases is preventable and reversible if it starts at an early age, namely in childhood and adolescence. In adulthood, it is more difficult to reverse.  

The covid-19 pandemic, with all its lockdowns and drastic changes in people’s lives, has brought new challenges in the fight against overweight and obesity.  Portugal faced three waves of covid-19. The first was from March to April 2020, followed by a second wave from October to November 2020, and a final wave from January to February 2021. To protect its citizens and contain the spread of the SARS-CoV-2 virus, the Portuguese government declared a state of emergency and implemented strict yet necessary measures to mitigate the effects of virus transmission – mandatory home confinement, closure of schools, restaurants, non-essential businesses and borders. Restrictions on the movement of people and goods and an unexpected, drastic change in lifestyles exacerbated the problem of overweight and obesity. In terms of the population, there is therefore an urgent need to focus on children and young people at risk, i.e. those that are overweight and obese, in order to outline new, more effective strategies to tackle this widespread public health problem.

In addition to the fundamental importance of monitoring nutritional status, current evidence indicates a need to monitor physical fitness in children and adolescents. Physical fitness is a state that reflects the ability to perform daily tasks efficiently, and it is associated with physical well-being and health. It is now accepted that physical fitness is also a marker of health status. Acquiring and maintaining a satisfactory level of physical fitness throughout one’s life is associated with a lower risk of developing chronic diseases, thereby playing a very important preventive role in the individual and collective health of populations.

With regard to children of healthy weight, it has been reported that those who are overweight are systematically less physically fit. This is a problematic issue that requires attention and intervention in order to promote the health and well-being of these children and prevent the development of pathological conditions in the future. It is therefore important to understand whether these relationships have been maintained following the pandemic. 

The RUSH project analysed the physical growth, motor development and health behaviours of primary school children following the covid-19 pandemic. This article focuses on the description of overweight and obesity prevalences in these children, comparing its values with national and European studies and probing into its links with physical fitness levels. We sampled 2,681 Portuguese children aged between 6 and 10 years from the mainland (Matosinhos, in the northern region; n=1,273) and the Autonomous Region of the Azores (n=1,408).

Table 1 shows the socio-demographic indicators of the two samples. In the Azorean families, 44% have 1 child, 51.9% have 2 or 3 children and only 4.1% have 4 or more children. In Matosinhos´ families, the frequencies are as follows: 24.6% have 1 child, 70.3% have 2 or 3 children and 5.1% have 4 or more children. In terms of the number of people living in the home, around 6.1% of children in the Azores live in a single-parent family, while in Matosinhos the frequency is 3.8%. About half of the Azoren (46.4%) and Matosinhos (51.6%) families have 4 members. Regarding mothers and fathers education levels, the following was observed: 28.6% of mothers and 46.6% of fathers from the Azores have only completed the first or second cycle of basic education. However, 32.3% of the mothers and 32.9% of the fathers had completed high school or its equivalent (vocational course), and 36.6% of the mothers had a degree or higher, compared to 23% of the fathers. In Matosinhos, 18% of mothers and 31% of fathers have only completed the first or second cycle of education, while 42.1% of mothers and 40.5% of fathers have completed secondary education or the equivalent. Finally, 39.8% of mothers and 28.6% of fathers have a university degree or higher.

RUSH results show that four out of ten children (44.1%) are overweight (including obesity). Girls and boys have similar rates (44.6% and 43.7% respectively). Azorean children have a significantly higher prevalence (49.1%) than Matosinhos children (38.6%).

Figure 2 shows the distribution of the prevalence of overweight and obesity between the ages of 6 and 10. In the case of overweight, the values tend to be more homogeneous between the ages, ranging from 19.2% in 6-year-olds to 22.0% in 10-year-olds. On the other hand, there is a greater variation in prevalence for obesity, from the lowest at age 6 (12.8%) to the highest at age 8 (25.5%), and 20.0% (1 in 5) at age 10.

Figure 3 shows the comparisons between the two locations: Matosinhos and the Azores. The prevalence of overweight is generally lower in Matosinhos children than in those from the Azores. In terms of obesity, the prevalence is higher for Azorean children of all ages. The trend is maintained for overweight, i.e. children from the Azores have higher prevalence rates than those from Matosinhos, except at 8 years of age (21.8% versus 24.0%, the Azores and Matosinhos respectively).

Children aged 6 years have the lowest prevalence of obesity in the Azores (13.8%) and Matosinhos (12.0%). In Matosinhos, higher prevalence of obesity occur at the age of 8 (23.0%), while in the Azores, it occurs between the ages of 7 and 9 (27.0%).

Figure 4 shows the probabilistic trend for children to be overweight (including obesity) between the ages of 6 and
10. Older children are about twice as likely to be overweight compared to younger children. This risk increases until the age of 8 and then decreases. Moreover, children from the Azores are 1.38 times more likely to be overweight than children on the mainland. Which group of children is most at risk? Children aged 8 and 9 from the Azores (the probabilities are 0.53 and 0.54, respectively). This means that one in every two children aged 8 or 9 from the Azores is likely to be overweight. In Matosinhos, children aged 8 and 9 are most likely to be overweight (0.43 and 0.42, respectively).

This section compares the prevalence of overweight (including obesity) in children from the RUSH project with the most recent information published by the COSI Portugal study (https://www.ceidss.com/pt/cosi-portugal/) in children aged 6-8 years and by the NCD Risk Factor Collaboration (NCD-RisC) network study published in The Lancet in March 2024 (https://doi.org/10.1016/S0140-6736(23)02750-2) in children aged 6-10 years. The data from the two studies refer to the years 2021 and 2022 – in a sense, during and after lockdowns, although there is a huge variation in the forms of lockdowns and their duration between countries. Despite the interpretative care taken because we are dealing with data of different scales and representativeness, it is important to refer to the RUSH project's results.

Figure 5 shows the comparisons of RUSH prevalences with those from COSI, considering the total sample for the country, the mainland sample in the northern region, and the Autonomous Region of the Azores. There is a 10.0% difference between the RUSH project and the COSI when considering the overall prevalence. However, the differences are not so pronounced when we look at the regions – on the mainland, 33.2% of children were overweight in the northern region and COSI, and 38.5% in the RUSH study. The difference between the two studies in the Autonomous Region of the Azores is only 2.4%.

When we compare the results by gender (Figure 6), three out of every ten children are overweight in the COSI Portugal study, while four out of every ten children present this condition in the RUSH study.

Finally, when we contrast the results of the two studies by age and gender (Figure 7), it is from the age of 7 onwards that the differences between the studies become more evident.

The second set of comparisons considers four clusters of children: the first refers to participants in the RUSH project, and the others are derived from the terminology used in the aforementioned paper from The Lancet (2): Central and Eastern Europe, high-income Western countries and all countries participating in the study.

The comparisons are shown in Figures 8 and 9. Girls and boys from the RUSH project have the highest prevalence of overweight. It is also important to note that the prevalence of overweight in girls aged 6 (30.0%) and 10 (39.0%) is very close to that in high-income Western countries (29.0% and 37.0%, 6 and 10 years respectively). The ages at which differences are noticeable are 7, 8 and 9. The boys in the RUSH project also have a higher prevalence of overweight than the other participants in The Lancet study, except at age 6.

Pysical fitness in the RUSH project was assessed by two main components: motor fitness and musculoskeletal fitness. Agility and running tests were used for the former, while muscle strength tests (handgrip and standing long jump) were used for the latter. Figures 10, 11, 12, and 13 indicate that overweight boys and girls (including obesity) are generally less physically fit than their normal weight peers. The exceptions are 6-year-old girls in the standing long jump and agility tests and 6-year-old boys in the speed and agility tests.

The differences in physical fitness between normal weight and overweight children tend to increase with age, except for the handgrip test – the differences are constant across age.

1.    The results of the RUSH project revealed that the prevalence of overweight and obesity in Portuguese children (Matosinhos and the Azores) following the covid-19 pandemic not only remains high but also in many cases is higher when compared to other studies at national and European levels. This fact calls for epidemiological surveillance.

2.    Moreover, it indicates that the prevalence of overweight and obesity is higher in children from the Azores when compared to children living in Matosinhos (northern region of the mainland). This result suggests the existence of regional differences in the prevalence of overweight, and these must be taken into account when designing and implementing intervention programs and monitoring them.

3.    This study also highlighted the negative impact of overweight on children’s physical fitness. This effect is more pronounced in older children.

It is important to bear in mind that the WHO and its Member States have set a target of halting the rise in obesity by 2025. The RUSH results suggest that this goal may be difficult to achieve in these places. The social, economic, and public health impact of childhood obesity is significant.

Despite the indications of the National Health Programme and its reference to combating childhood obesity (https:// www.dgs.pt/em-destaque/plano-nacional-de-saude-revisao-e-extensao-a-2020-aprovada-pdf.aspx), as well as the general indications of the official Physical Education Programme in the primary school on the importance of developing physical fitness ( http://www.dge.mec.pt/educacao-fisica), we would like to make the following suggestions:

1.    There is an urgency to develop new approaches to weight management from an early age, including greater involvement of schools, families, and the children themselves. These approaches must also consider the educational departments of local city-hall councils, given their importance in school communities and the group of physical education teachers.

2.    Actions must aim to educate children about healthy lifestyles, focusing on adopting more balanced eating habits designed by nutritionists who prepare school meal plans. They should also encourage families to adopt a more consistent approach to their eating habits.
 
3.    It is important that local city-hall councils, through their education departments, incorporate into their political agenda an increase in the number of physical education classes in primary schools – from one to two classes per week over the four years of schooling. The ideal should be three classes a week.

4.    It is important that the development of fundamental movement skills be given a high priority in physical education classes or in children’s introductory sports training, as this is the best guarantee of widespread participation in moderate-to-vigorous physical activity, which has a cumulative effect on children´s perceptions of motor competence. Furthermore, this will increase their physical fitness levels and helps to regulate their body weight.

5.    Sports clubs and coaches who work with children must also be involved in this ‘battle’ by developing and monitoring new approaches so that all children, including those who are overweight or obese, feel successful in a wide range of training and competitive activities. No child should be left behind.

In sum, close coordination between different social players is mandatory: families, school communities, local health organizations, sports clubs, and local authorities. The sharing of responsibilities, the implementation of programs with achievable goals, and their monitoring are windows of opportunity expected to be effective and sustainable in halting and reversing the systematic increase in overweight and obesity. This will also increase the time devoted to moderate-to-vigorous physical activity, physical fitness, and sports participation during the primary school years.