Weight status

1. Key messages

2. Background

Overweight and obesity are defined as an excessive accumulation of body fat, which favors the development of chronic diseases (diabetes type 2, cardiovascular diseases, cancers). The body mass index (BMI), calculated as the weight divided by the square of the height, is a simple tool allowing to classify the weight status into broad categories: underweight, normal weight, overweight, and obesity. In adults, obesity is defined as having a BMI ≥ 30. A person is considered overweight if they have a BMI ≥ 25, a definition including overweight-non obese as well as obese people. It is to be noted that the same term (overweight) is sometimes used to designate overweight-non obese people (BMI between 25 and 29.9). To avoid any confusion, in this report, it will be always specified if overweight percentages include obesity or not. In children and adolescents, the cut-offs of the BMI categories are age and sex-specific, the cut-offs recommended by the International Obesity Task Force (IOTF) [1] are used.

The BMI categories can be assessed either from self-reported information about weight and height, such as that collected in the Health Interview Survey (HIS) [2] and the Health Behavior in School-aged Children survey (HBSC) [3,4], or from measured information such as that collected by the Health Examination Survey (HES) [5] and the Food Consumption Survey (FCS). The HES is a subsample of the HIS; for 1184 participants in the HIS a second visit was realized by a nurse who performed physical measurements and collected biological samples. Self-reported data usually lead to some underestimation of the true overweight/obesity prevalence. People are not exactly aware of their exact height and weight and tend to overestimate their height and underestimate their weight.

We first present results for the adult (18+) population. The prevalence of self-reported overweight and obesity are based on the HIS 1997 to 2018 data, and that of measured weight status on the HES 2018. Results for adolescents are based on the HBSC surveys conducted in the Flemish and the French Community. We computed a Belgian average based on the results by community. For socio-economic disparities and international comparisons, data are used from the most recent international reports published by the World Health Organization.

More information about the cost of overweight and obesity can be found in a dedicated factsheet.

More information about the projected prevalence of overweight and obesity in the future can be found in a dedicated factsheet.

3. Overweight and obesity in adults

Situation in 2018

Belgium

According to the HIS, based on self-reported height and weight, the prevalence of overweight (including obesity) was 49% and the prevalence of obesity was 16% in 2018. More men (55%) than women (43%) were overweight (incl. obesity), and more men (17%) were obese than women (15%) (the latter is however not significant).

According to the HES, the prevalence of overweight (including obesity) (55%) and obesity (21%) based on measured height and weight were higher than those based on self-reported data. The difference between self-reported and measured rates was higher among women.

The measured prevalence of overweight (incl. obesity) was higher among men (59%) than among women (52%), as was the case for the self-reported prevalence. The measured prevalence of obesity was higher among women (23%) than among men (20%), but this difference was not statistically significant.

The prevalence of self-reported overweight (incl. obesity) increased with age until the age group of 65-74 years where it reached a peak in both men (68%) and women (56%); it then decreased among people aged 75 and older, in both sexes. This increase starts earlier in men (25-34 years) than in women (35-44 years).

Self-reported obesity follows the same age pattern as overweight and reached its highest level in 65-74-year-olds, in both men (26%) and women (20%).

Regional differences

The prevalence of both overweight and obesity was higher in Wallonia than in the other regions in all HIS waves and in both sexes.

Trends

At the Belgian level, the prevalence of overweight (incl. obesity) has continuously increased when considering both sexes together. From 2013, the prevalence remained stable among men but continued to increase among women. The prevalence of obesity also slowly and continuously increased over all HIS waves, with a stronger increase between 2013 and 2018.

Regional differences

At regional level, the prevalence of overweight and obesity has always been higher in Wallonia than in the other regions. Among men, the trends of obesity and overweight were similar, and similar to the ones described for Belgium; among women, a stabilization of overweight and obesity was observed in Flanders.

Socio-economic differences

Overweight, and even more obesity, are associated with the educational level. The lowest educated group (61%) had a prevalence of overweight (incl. obesity) 1.5 times higher than the most educated group (41%). There were two times more people obese among the less educated (23%) compared to the most educated (12%).

International comparison

The prevalence of overweight (incl. obesity) was lower in Belgium than the EU-15 average, both in men (54.4% versus 57.6%) and in women (43.5% versus 44,8%).

4. Overweight and obesity in adolescents

Situation in 2018

In 2018, the prevalence of overweight (incl. obesity) in adolescents was around 15%, calculated as the average of the estimates in the French and Flemish HBSC 2018. It was higher among boys (15.5%) than among girls (14.5%) and tended to increase with age (the statistical significance is unknown). The lowest prevalence (around 13%) was observed among the younger girls (11-14 years) while the highest prevalence (around 16%) was observed among boys aged 15-16 years and girls aged 17-18 years.

The prevalence of obesity in adolescents was 4.0% among boys and 3.6% among girls and was relatively similar across age groups.

Trends and differences between Communities

In 2018, overweight (incl. obesity) prevalence among 15-year-old adolescents was slightly higher in the French than in the Flemish Community. This was especially pronounced among boys, with an overweight prevalence of 19% in the French Community and 13% in the Flemish Community (the statistical significance is unknown). Overweight prevalence among girls was more similar in both Communities.

The overweight prevalence increased between 2006 and 2014 in each Community and for both sexes. Between 2014 and 2018, among boys, the prevalence decreased in the Flemish Community while it continued to increase in the French Community. Among girls, the overweight prevalence increased in a same way in both Communities.

Trends in obesity prevalence are not available at the moment.

Socio-economic differences

According to the HBSC report, being overweight (incl.obesity) is associated with low family affluence for both sexes. In the Flemish Community, boys and girls from the lowest socio-economic group were 1.8 more likely to be overweight than boys and girls from the higher socio-economic group. In the French Community, boys and girls from the lowest socio-economic group were respectively 2 times and 3 times more likely to be overweight than boys and girls from the higher socio-economic group. Low- and high-affluence groups represent the lowest 20% and the highest 20% in each Community.

International comparison

Based on the results for 2018, Belgium ranks quite favorably among the EU-15 countries with an overweight prevalence of 16.1% compared to 20.7% for the EU-15 average among boys. The prevalence of overweight is similar to the EU-15 average among girls (14.3% in Belgium, 14.5% for EU-15).

5. Read more

View the metadata for this indicator

HISIA: Interactive Analysis of the Belgian Health Interview Survey

Health-Behaviour in School-aged Children (HBSC) survey - French Community

Health-Behaviour in School-aged Children (HBSC) survey - Flemish Community

Definitions

Body mass index (BMI)

The body mass index (BMI) is a measure of a person’s weight relative to their height that is reasonably well related to body fat. It is calculated as a person’s weight (in kilograms) divided by the square of his/her height (in meters).

BMI categories

In adults:
• Underweight: is defined as a BMI lower than 18.5.
• Normal weight: is defined as a BMI range of 18.5-24.9.
• Overweight: is defined as a BMI between 25.0 and 29.9. We often referred to overweight including obesity i.e. with a BMI ≥ 25.
• Obesity: is defined as a BMI ≥ 30.
In children and adolescents, the cut-off points to define BMI categories are age and sex-specific.

EU-15

The EU-15 corresponds to all countries that belonged to the European Union between 1995 and 2004: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Portugal, Spain, Sweden, and the United Kingdom. We compare the Belgian health status to that of the EU-15 because these countries have a similar socio-economic situation.

References

1. International Obesity Task Force. https://www.worldobesity.org/about/about-obesity/obesity-classification
2. Health Interview Survey, Sciensano, 2018.  https://www.sciensano.be/en/projects/health-interview-survey
3. HBSC French Community, ULB, 2018. http://sipes.ulb.ac.be/
4. HBSC Flemish Community, UGent, 2018. http://www.jongeren-en-gezondheid.ugent.be/
5. Health Examination Survey, Sciensano, 2018.https://www.sciensano.be/en/projects/health-examination-survey
6. Eurostat. http://ec.europa.eu/eurostat/fr/data/database
7. Inchley J et al. eds. Growing up unequal: gender and socioeconomic differences in young people's health and well-being. Health Behaviour in School-aged Children (HBSC) study: international report from the 2013/2014 survey. Copenhagen, WHO Regional Office for Europe, 2016 (Health Policy for Children and Adolescents, No. 7). http://www.euro.who.int/__data/assets/pdf_file/0003/303438/HSBC-No.7-Growing-up-unequal-Full-Report.pdf?ua=1
8. Currie C et al. eds. Social determinants of health and well-being among young people. Health Behaviour in School-aged Children (HBSC) study: international report from the 2009/2010 survey. Copenhagen, WHO Regional Office for Europe, 2012 (Health Policy for Children and Adolescents, No. 6). http://www.euro.who.int/__data/assets/pdf_file/0003/163857/Social-determinants-of-health-and-well-being-among-young-people.pdf?ua=1
9. Currie C, Nic Gabhainn S, Godeau E, Roberts C, Smith R, Currie D, Pickett W, Richter M, Morgan A & Barnekow V (eds.) (2008). Inequalities in young people's health: HBSC international report from the 2005/06 Survey. Health Policy for Children and Adolescents, No. 5, WHO Regional Office for Europe, Copenhagen, Denmark. http://www.euro.who.int/__data/assets/pdf_file/0005/53852/E91416.pdf?ua=1
10. Inchley J, Currie D, Budisavljevic S, Torsheim T, Jastad A, Cosma A. Spotlight on adolescent health and well-being. Findings from the 2017/2018 Health Behaviour in School-aged Children (HBSC) survey in Europe and Canada. International report. Volume 2. Key data [Internet]. Copenhagen: WHO Regional Office for Europe; 2020 [cited 2020 Jun 15]. Available from: https://www.euro.who.int/en/health-topics/Life-stages/child-and-adolescent-health/health-behaviour-in-school-aged-children-hbsc/publications/2020/spotlight-on-adolescent-health-and-well-being.-findings-from-the-20172018-health-behaviour-in-school-aged-children-hbsc-survey-in-europe-and-canada.-international-report.-volume-2.-key-data
11. OECD Health at a Glance 2020. https://www.oecd-ilibrary.org/social-issues-migration-health/health-at-a-glance-europe-2020_82129230-en

Please cite this page as: Sciensano. Determinants of Health: Weight status, Health Status Report, 01 July 2020, Brussels, Belgium, https://www.healthybelgium.be/en/health-status/determinants-of-health/weight-status