Some children can 'outgrow' obesity, says study in The Lancet
The new model, published in The Lancet Diabetes & Endocrinology, indicates that some children may be able to 'outgrow' obesity during key periods of rapid growth, particularly between the ages of 11 and 16, and without the need to actually lose weight.
Led by Dr. Kevin Hall from the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda (USA), the model is the first to actively differentiate between the healthy weight gain that is normal in childhood, and the excessive levels which result in obesity.
The model accurately represents how energy balance in children is responsible for weight gain. This is the difference between the total consumed energy and the amount which is actually expended.
Current models may have hugely underestimated the amount of calories which overweight or obese children are eating. For example, models currently used by clinicians predict that a girl who was a healthy weight at age 5, but is now 10kg overweight at age 10 has an excess calorie intake of around 40kcal per day. This is measured as being the approximate calorific content of a small apple.
However, the new model is based upon a more sophisticated understanding of how metabolic function, growth and energy expenditure change as children gain weight. This estimates that in actuality, the same overweight 10 year old is consuming closer to 400kcal per day more than her healthy peers. In contrast, this is measured as being the approximate calorific content of a beef burger or medium portion of fries.
This model also suggests that due to the aforementioned interaction between growth rate, metabolism and energy expenditure it may be possible for some children to actually 'outgrow' obesity during periods of rapid growth, most exhibited between 11 and 16 years of age.
Boys who are obese over this period will tend to normalise their body fat levels while continuing to grow taller and add lean tissue mass. However, this effect is less pronounced in girls, primarily because they lose less body fat during this period and do not have as high a growth potential.
By testing this model against real-world data from studies assessing the effect of various weight-loss interventions, the research team were able to show that their model is so far the most accurate tool developed to predict the effect of calorie intake on child weight loss.
With roughly one-third of children in the UK and US estimated to be overweight or obese, the new model may provide clinicians and policy-makers with a vastly improved understanding of how calorie-controlled dieting and physical exercise regimes can be utilised effectively in order to address the epidemic of childhood obesity.
Dr. Hall said:“One of the most disconcerting aspects of the global obesity epidemic is the high prevalence of childhood obesity, which carries both health and economic consequences.
"The model we have developed is a substantial step forward in fighting this rising tide of childhood obesity. It allows us to accurately predict how a child’s energy intake affects his or her likelihood of becoming overweight or obese.
“Though the model doesn’t apply perfectly to all children – for instance, those who start adolescence late, or who undergo particularly rapid weight gain – it provides an accurate representation of the average effect of reducing or increasing calorie intake on the weight of children.
"Our future research will adapt the model to individual children as well as study the effects of increasing physical activity along with diet changes.”
Also commenting on the research, Professor Claudio Maffeis from the University of Verona, Italy, suggests that the best time for implementing weight loss plans in children is likely to be before puberty, particularly in order to further prevent obesity in girls, since they do not have as great a capacity to regulate their fat levels.
However, if childhood obesity is to be effectively tackled, awareness of correct portion sizes and calorific intakes must be instilled in both parents and children.
“The accuracy of parents’ awareness of children’s portion sizes and reporting of children’s food intake is only moderate,” says Professor Maffeis.
He added that: "To translate into practice these desired changes in energy balance, it will be necessary to increase families’ knowledge and awareness of energy content and composition of childrens’ diets by designing effective and sustainable educational programmes about nutrition.”