At the most basic level, the systematic collection of obesity data enables us to determine the number of individuals living with the disease.
When routine and standardised, obesity monitoring and surveillance also allows us to examine trends and monitor the progress and effectiveness of obesity-related programmes, interventions and initiatives. Large, nationally representative surveys can also help identify which subsets of populations are most at risk.
Such evidence can – and should - be used to support advocacy. It can also help justify government and non-governmental action where it's needed. This is why the ROOTS Declaration - which was launched on World Obesity Day 2020 - emphasises the importance of obesity data collection.
Status of obesity monitoring and surveillance
Many countries undertake some level of monitoring and surveillance, but standards vary widely between them. Reasons for such variation can only be speculated but may include lack of political commitment and inadequate research funding. In recent years, in particular, we have seen planned surveys and research studies put on hold as public health attention has been diverted to the ongoing COVID-19 pandemic.
There tends to be three ways in which obesity monitoring and surveillance are conducted. The first is within obesity-specific studies, the second is within country-specific national health surveys and the third is within standardised surveys that are used across countries.
The WHO European Childhood Obesity Surveillance Initiative (COSI) is an initiative that has measured trends in overweight and obesity in primary school-aged children for over 10 years. The initiative is an example of both obesity-specific monitoring and surveillance and one that is standardised across countries.
Another example of obesity-specific surveys includes the many one-off studies completed by researchers who measure overweight and obesity within set populations. While these studies often are “one-offs”, they play an important role in providing us with a “snapshot” of the situation, particularly when national surveys are absent.
National health surveys
Many countries also conduct regular, national health surveys. An example of this is in Mexico, where a flagship National Health and Nutrition Survey (Encuesta Nacional de Salud y Nutrición) is conducted approximately every two years. This survey collates prevalence and trend data (broken down by population) on several different indicators of health and nutrition including overweight and obesity. The survey uses large, nationally representative samples, and the results are based on measured weight and heights.
New Zealand has a similar monitoring programme in place. In both of these examples, standardised methodologies are used each time with appropriately trained personnel. The use of the same methodology over regular time intervals allows the collection of useful trend data.
Standardised cross-country surveys
The last way in which obesity monitoring and surveillance are commonly conducted is in standardised cross-country surveys. These are surveys that are conducted in several countries using the same methodology. Examples of such standardised surveys include the Demographic Health Surveys (DHS) and WHO STEPwise Approach to NCD Risk Factor Surveillance (STEPS). To date, the DHS programme has conducted over 400 surveys in over 90 countries. Similarly, the STEPs programme has been conducted across many countries but focuses especially on non-communicable disease risk factors.
Such standardised surveys are commonly used by lower-income countries, therefore providing a template that can be used in places where resources are scarce. Unfortunately, these surveys are not undertaken routinely, and so despite being helpful for sharing ‘snapshots’, they are less useful in providing evidence on obesity trends.
Global Obesity Observatory
Our Global Obesity Observatory utilises all of the previously mentioned surveys to give “snapshots” on obesity prevalence worldwide. Unfortunately, however, many countries still rely on irregular one-off studies and so trend evidence on obesity is often poor.
We call for more investment and political prioritisation of obesity monitoring and surveillance so that governments and policymakers around the world can better keep track of progress or the lack thereof. Fully funded and regular national health surveys should be a national priority to help monitor obesity and other communicable and non-communicable diseases. It is only then that we can properly track our progress in meeting national and international targets.