What is the benefit of using stable isotope techniques to assess energy expenditure?
- Childhood obesity is increasing worldwide — from 4.2% in 1990 to 6.7% in 2010. Of 43 million children under 5 years of age with excess weight, 32 million are in developing countries. In Latin America, approximately 7.1% of children who are below 5 years of age and between 17% and 37% of school age children and adolescents are overweight;
- Physical inactivity and poor diet quality are risk factors for obesity and related non-communicable diseases (NCDs);
- Total energy expenditure (TEE) can be assessed using the doubly labelled water (DLW) technique;
- The DLW technique is the only way to accurately measure the amount of energy a person uses each day, as they go about their normal activities;
- The DLW technique gives an estimate of energy requirements, and can be used at any stage in life;
- The DLW technique can be used to assess the impact of interventions to increase physical activity.
Physical activity is an integral part of the school day in Chile. (Photo: S. Gorisek, IAEA)
How does it work?
- A person drinks a dose of water containing two stable, non-radioactive, isotopes (deuterium (2H2O) and oxygen-18 (H218O)). The dose mixes with the water in their body. The isotopes leave the body in urine, sweat and breath;
- Urine samples are collected before administration of the dose and for 7-14 days after the dose was given;
- Deuterium is lost only in water, whereas oxygen-18 is lost in both water and carbon dioxide. The difference in the elimination rates of deuterium and oxygen-18 (the slope of the lines in the graph) is a measure of carbon dioxide production rate, from which energy expenditure can be calculated.
Tackling childhood obesity in Chile
- Obesity is a major risk factor for the development of NCDs later in life;
- The increasing prevalence of childhood obesity in Latin America has become a cause for concern, and needs to be addressed early in childhood;
- Since 1997, the IAEA has worked closely with the Institute of Nutrition and Food Technology (INTA), University of Chile, to address the problem of childhood obesity in the country;
- Studies conducted with the support of the IAEA, focused on energy expenditure and body composition in children aged 4-5 years attending day care centres in Santiago. The first study showed that the children consumed 10% more energy than is recommended for children of this age. They were also found to be physically inactive;
Structured exercise is part of the curriculum at a day care centre in Santiago, Chile. (Photo: S. Gorisek, IAEA)
- Based on this information, an intervention programme with advice on healthy eating and physical activity was developed, implemented and periodically evaluated with the support of the Ministry of Health and the National Institute of Sports in Chile and the IAEA's Technical Cooperation Programme to assess the impact;
- The physical activity programme was incorporated into the curriculum of the day care centres, and was subsequently adopted by the national authorities in Chile;
- Chile is the only country in Latin America that has successfully halted the rise in childhood obesity in pre-school children. The latest statistics show that between 2000 and 2010, the rate of obesity in children attending day care centres dropped from 10.4% to 8.4%.
Educational resources produced by the Chilean National Institute of Sports. (Photo: B.T. Gebka, IAEA)