This study assessed the association between weight gain and changes in health behaviours, such as unhealthy nutritional habits, physical inactivity and alcohol consumption, during the 6- weeks confinement period (from the 13th of March until the end of the second COVID-19 health survey on the 23th of April 2020). More than a quarter (28.6%) of the adults reported weight gain over this period in Belgium. Persons who already suffered from overweight or obesity reported weight gain more frequently. Weight gain during confinement has also been reported in other studies: 22% of adults in the US sampled by Facebook reported gaining weight during self-quarantine due to COVID-19 (23) and 49% of the Italians (survey organised between the 5th and 24th of April 2020, after 7 weeks of confinement) (24).
An increased consumption of sweet or salty snacks and being less physically active during this period both appear to be important health behaviour changes associated with weight gain during the confinement period. These behaviours were also found to be major risk factors in other studies (23, 25, 26). Eating unhealthy food and being physically inactive tend to co-exist (27).
The proportion of persons who indicated having increased their consumption of food prepared out-of-home during confinement is low, which is not surprising due to the closure of bars and restaurants. An increased consumption of alcohol was also found to be a risk factor for weight gain during confinement. On the other hand, the confinement also had a positive influence in some respects. For instance, women who decreased their alcohol consumption had lower odds of weight gain. The closure of bars and restaurants had undoubtedly an impact on the alcohol consumption, especially for social drinkers and youngsters who could not go out anymore whereby their lower consumption. However, other people possibly consumed more alcohol at home during confinement.
In case of a next epidemic wave, it is necessary that policy makers pay a greater attention to these unintended consequences, so that the prevalence of overweight and obesity does not continue to increase. According to the second COVID-19 health survey during the confinement, 19,0% of the Belgium adults were classified as obese, a prevalence that was significantly higher than that of the national Health Interview Survey in 2018 (15,9%) (13). It will be important to consider our eating habits, especially with regard to the consumption of sweet and salty snacks. A balanced diet, rich in nutrients and antioxidants, not only helps controlling our body weight (4–6), it also helps to have a strong immune system (24, 28, 29). It is crucial, especially during confinement, to keep good dietary habits including fresh fruits, vegetables, whole grains, plant and animal protein and healthy fats. In addition, hydration is important and water is the healthiest and cheapest way to do this (29). Beyond the direct effect of unhealthy eating and increased obesity during the confinement measures, the COVID-19 pandemic further amplified the burden of obesity by more severely affecting people with overweight or obesity. This highlights the need for more ambitious policies to address the multiple determinants of obesity and unhealthy eating in Belgium. Potential policy actions could be labelling to help people making healthy food choices, legislation to end the promotion of foods high in fat, sugar or salt (HFSS) and banning the advertising of HFSS products on TV and online.
Besides a healthy diet, staying active during confinement is also an important health behaviour, not only for controlling the weight status, but also for the well-being and the quality of life (30). In Belgium, even with the confinement measures, the population still had the opportunity to go outside, but in their local environment. Additionally, the combination of good weather conditions during this period and more free time due to a change in the work situation for some people made it easier to be active. This was also observed in this survey since 47.5% of the population has indicated that their physically activity habits remained the same and even 23.8% was more physically active in this period. Nevertheless, 28.8% of the adults were less physically active in this period, which could be attributed to confinement measures such as closure of indoor sport facilities, or the extra burden of home schooling because of school closure.
This study has several strengths. Firstly, the online tool made it possible to react rapidly to the crisis. The first COVID-19 health survey was launched only three weeks after the confinement. A web survey not only has financial advantages, but also logistical ones (automatic data entry, user-friendly by checks and automatic branching logic) whereby high quality data were instantly available (31, 32). Moreover, the survey could be answered on several devices like a mobile phone, a tablet and computer that makes it very accessible. Another strength is that a large sample of the population aged 18 years and older was collected on a convenience sample. Although it is a fast method of sampling, it is also a more biased process since there is no randomisation (21). Consequently, the composition of our sample differed from the composition of the general Belgian population aged 18 years and older. An overrepresentation of women and higher educated people, as well as an underrepresentation of elderly was also established in the French NutriNet-Santé cohort study who also applied weights in the analyses to improve the representativeness of the population (26). Besides elderly and low educated people are also the groups that are less motivated to participate in other web surveys (33). The last shortcoming of this study is that self-reported data may be related to misreporting (24). It is well known that the BMI based on self-reported measures is often underestimated (3).