Mediators of effective energy-balance interventions in youth

Obesity prevention in youth requires effective interventions targeting the so-called energy balance-related behaviours (that is, physical activity, sedentary and dietary behaviours). To improve (cost-)effectiveness of these interventions, we need to know the working mechanisms underlying behavioural change. Mediation analyses is a technique that helps to explore an analyse via what pathways interventions have their effects (...or not). Identifying such mediators of intervention effects can help professionals in developing new interventions or adapting existing interventions so that these are targetted at these succesful mediators as good as possible. Dr. Maartje van Stralen and colleagues just published a systematic review of studies on  identification of psychosocial and environmental mediators of  school-based interventions for youth, aiming to change physical activity, dietary and/or sedentary behaviours. The review paper was published in the International Journal of Obesity and was conducted as part of the ENERGY project, a cross-European and European Commission funded project to inform effective prevention of overweight and obesity in schoolchildren across Europe. Twenty-four studies were identified in the scientific literature. Based on the review of these 24 studies, strong evidence for self-efficacy and moderate evidence for intention as mediators of physical activity interventions was found, i.e. improvements in physical activity were brought about via positive changes in self-efficacy and intentions. Some evidence was found that attitudes, knowledge and habit strength were mediators of dietary behaviour interventions. Too few studies were avialbale on interventions aiming to reduce sedentary time to draw any conclusions regarding potential mediators.

KLV 125 years

The Wageningen University and Research Center Alumni network (KLV) celebrates its 125 year anniversary this year. Part of the celebrations is a series of presentations and debates on emerging topics regarding food, nutrition and agriculture, with ‘How to feed the World’ as the over-arching theme. Yesterday afternoon I presented at one of these debate sessions in Nieuwspoort in the Hague.


The topic of the afternoon was how healthy and sustainable food and nutrition can and should go together. The debate focussed on whether promotion of healthy and sustainable food should be primarily be pursued via health education to encourage well-informed healthy choices, or more via health protection measures, i.e. by changes in the availability and accessibility of foods in order to make the healthy and sustainable choice more or less the ‘default’ choice.

The great public health promotion accomplishments (the US Centers of Disease Control (CDC) as well as for example the department of Public Health of Erasmus University Medical Center have made overviews succeses of prevention as well as   of the past were mostly the result of health protection measures. Two well-known examples are the building of drinking water and sewage systems that has resulted in the almost disappearance of some major infectious diseases; and traffic safety measures have resulted in an impressive reduction in (fatal) traffic accidents.

Recent research shows that our dietary choices are strongly influences by environmental cues, i.e. by what is easily available and accessible. And in our fast food nations, some of the most readily available and almost unavoidable foods are high calorie-low nutrient foods like sweet and savoury snacks, sugar-sweetened drinks.

the impact of too much sitting...

A recent systematic review conducted by Dr. Mai Chinapaw and colleagues, published in the journal Obesity Reviews, focusses on the possible health consequences of sedentary behavior. Recent research indicates that sedentary behavior, often operationalized as TV-time and other screen viewing behaviors, is associated with higher risk for being overweight and obese, as well as (other) metabolic health problems. the effects of sedentary behavior appear to be rather independent of physical activity, i.e. even when people do exercise a lot, sitting for prolonged periods of time may still increase their risk. The aim of this systematic review was to describe the prospective relationship between childhood sedentary behaviour and health indicators. 31 studies were indentified in data bases of scientific publications. In these studies 27 different cohorts were investigated. The systematic review of these studies confirmed that more  'sedentary time'- mainly TV viewing - predicts a higher body mass index (BMI) and other indicators of body fat. Evidence was also found that more sedentary time is associated with lower fitness levels, but no convincing evidence was found that sedentary time is associated with higher blood pressure, blood lipids or lower bone mass.

The successes of prevention in the Netherlands.

On March 11, the department of Public Health of Erasmus University Medical Center celebrated its 40 anniversary with a symposium on the success of prevention in the Netherlands, in the period of 1970-2010. The symposium was well attended by almost all experts in the field, as well as representatives of policy and practice organisations.


The head of the department, Prof Johan Mackenbach provided an overview of the success of prevention. This overview is more extensively documented and described in the book that he edited on the topic (see the picture), and illustrated in a short documentary.

Mackenbach argued in his presentation that the successes of prevention are often rather unnoticed, because, indeed successful prevention prevents ill health or mortality, i.e. it prevents an event from happening. This relative invisibility of the success of prevention may be one of the important reasons why policy makers have less attention for prevention and are often less willing to invest in prevention (only a few percent of the national health care budget is invested in prevention).

The successes presented by Mackenbach were identified based on the following criteria:

1. The effectiveness of the preventive action, policy or intervention should be scientifically well-documented

2. The effect of the preventive intervention should have clearly caused a reduction in mortality or morbidity because of the disease that the intervention was aiming to prevent

The team that did the analyses came up with 5 fields of prevention, i.e. prevention regarding pregnancy and youth care, prevention regarding work & health, prevention of accidents and injuries, promoting health lifestyles, and medical preventative interventions.

In terms of prevention of deaths, the antismoking efforts were by far the most successful prevention intervention in the last 40 years, with more than 6900 deaths prevented per year. Other important successes are the removal of trans fatty acids from foodstuffs (1500 deaths per year avoided), the screening on and treatment of high blood pressure (3000 per year), and traffic safety measures (2000).

Writing papers for the energy project

The last few days I spend in Ghent. Part of the team of the Energy project met there to write a series of scientific papers on overweight, obesity and energy balance behaviors in European schoolchildren. Papers were prepared on the validity of the questionnaires used for data collection in the project, on sedentary behaviors among the children and the relation with metabolic function, and on mediators and moderators of dietary, physical activity and sedentary behaviors. All these papers are prepared to further inform obesity prevention efforts in this important target group.

Bregje Onwuteaka Philipsen inaugurated

Today prof. Bregje Onwuteaka Philipsen accepted her chair in End of Life Research. In the Netherlands about 135,000 people die annually. For about 90,000 of these people, their end of life is something they foresee and something they and their important others can prepare for in this phase of end of life care. Bregje Onwuteaka Philipsen, a recent 'Vici laureat', i.e. she received one of the most prestigious personal research grants available in the Netherlands, has conducted and will conduct and lead important research to inform and improve end of life care. In her inaugural address she provided an overview of work accomplished and work to be done.

Active transportation, e.g. walking or cycling to school or work, may contribute to energy balance, i.e. preventing unwanted weight gain, and prevent becoming overweight. Some studies have been conducted looking at the association between  active commuting to school and weight status among youth, but no clear conlusion can be drawn. Some recent studies suggest that cycling to school may make a bigger difference than walking to school. The purpose of our study, recently published in the Scandinavian Journal of Medicine and Science in Sport, (with Dr. Elling Bere as first author) was to assess the association between cycling to school and weight status in two cities, Rotterdam and Kristiansand, i.e. in the Netherlands and Norway, two countries where cycling to school remains common. Data from two studies, ENDORSE (Rotterdam) and Youth in Balance (Kristiansand), were used including, respectively, 1361 and 1197 adolescents around 14 years old. The adolescents were categorized as cyclist or non-cyclist based on questionnaires asking them about their usual mode of transportation to school. Twenty-five and 18% were categorized as overweight, and 35% and 31% were categorized as cyclists, in Rotterdam and Kristiansand, respectively. Further analyses showed that youth who cycled to school were about half as likely to be overweight than their peers who did not, after adjusting for a range of other possible 'reasons' for being overweight. These results thus suggest that cycling to school may 'protect' against overweight, but more rigorous research is necessary.