The double burden of malnutrition: Malnutrition in early life can lead to overweight or obesity in adults. (Photo: INCAP/CIIPEC)
What is the benefit of using stable isotope techniques to assess body composition?
- Malnutrition caused by a poor-quality diet can result in loss of lean tissue (mainly muscle wasting) or excess body fat. Both have consequences for health. Simply measuring body weight cannot provide this key information;
- Body composition in terms of the relative amounts of fat and lean tissue is an indicator of nutritional status reflecting the quality of the diet;
- In many low and middle income countries, under-nutrition and obesity exist together in the same family; sometimes in the same person. This is the double burden of malnutrition;
- The body can be thought of as being composed of two categories: Fat mass, and fat-free mass. Water is only found in the fat-free mass;
- The amount of water in the body can be measured by isotope dilution using stable, non-radioactive, isotopes of hydrogen (2H) or oxygen (18O);
- Stable isotope dilution techniques can be used in community settings. The samples are taken back to the laboratory for analysis.
A field worker speaking with children during a lunch break at an urban primary school in Guatemala. (Photo: INCAP/CIIPEC)
How does it work?
- If a person drinks an accurately weighed amount of water labelled with deuterium (2H2O) or oxygen-18 (H 218O), the labelled water mixes with the water in their body. Aftera few hours, the isotope is evenly spread throughout the body water, which can be sampled in the form of saliva or urine. The amount of water in the body is known as total body water, and can be calculated from the dilution of the isotopes;
- The fat-free mass (FFM) is 73-80% water. At birth, the hydration of the FFM is approximately 80%. This gradually gets less as children grow and their bodies mature. By the time they are adults, the FM contains approximately 73% water;
- If we measure total body water, we can calculate FFM using an appropriate hydration factor;
- Body weight is the FFM + Fat mass. Therefore the amount of fat mass is the difference between body weight and FFM. Sometimes the results are expressed as a percentage of body weight.
Guatemala works to control the double burden of malnutrition
- Guatemala has one of the highest rates of chronic malnutrition worldwide; due partly to lack of protein and micronutrients in the diet which is composed mainly of high carbohydrate foods. Tackling this issue is a key priority for the government;
- With the help of nuclear techniques, scientists and health workers in Guatemala are now able to identify the causes and consequences of malnutrition in the country's children, enabling policymakers to devise strategies to combat obesity and stunting;
- Poor quality diets in infancy can lead to obesity later in life. Monitoring body composition is important, because changes in body composition are associated with physiological changes in the body that can lead to non-communicable diseases;
- While obesity is the main health challenge among children in the cities, the indigenous population in rural areas, mostly suffer from the opposite problem. Nearly eight out of ten children of indigenous origin are stunted (short height for their age) compared to four out of 10 children, who are not indigenous Guatemalans. The latest research has shown that, contrary to popular belief, the short stature of indigenous Guatemalans is not due to genetics. It is caused by inappropriate feeding practices and poor diet in the early years of life;
- With the information and data collected under IAEA projects, a task force endorsed by eight health ministers from Central America was established in June 2014 to develop a regional policy on the prevention and management of obesity in children and adolescents. Nutrition programmes include increasing the intake of vitamins and minerals through food fortification or micronutrient supplementation, and advocacy for healthy eating and increased physical activity.