A critique of models for body composition and energy-balance components in childhood and adolescence

QA Mathematics;RJ101 Child Health. Child health services

Haig, Caroline E ; McColl, John H.

University:University of Glasgow

Department:School of Mathematics and Statistics

关键词: Statistical modelling;    missing data;    MICE;    longitudinal simulation;    energy-balance;    energy intake;    energy expenditure;    overweight and obesity;    ALSPAC;    DEXA;    BIA;    pubertal staging;    healthy growth.;   

Others  :  http://theses.gla.ac.uk/4386/1/2013haigphd.pdf

来源: University of Glasgow

【 摘 要 】

It is well known that, in Western countries, people of all ages and both sexes are becoming ‘fatter’ in general. In a ‘healthy’ population, we arbitrarily consider cut-offs to be that 10% of people should be ‘overweight’ and 5% ‘obese’, as there is limited evidence that these cut-off points are related to ill-health. However, we are seeing a dramatic rise in the numbers of people in each of these categories. The mechanism behind weight gain is energy-imbalance. At energy-balance for adults - i.e. where weight is expected to remain stable over time, we know that:energy intake (EI) = energy expenditure (EE)This equation is far less straightforward than it first appears. The first important issue is that EE has several different components (e.g. resting EE). The second issue is to do with measurement - how do we measure energy intake andenergy expenditure? Another is down to physiological differences between people - how do things vary between individuals and do they differ systematically betweenmales and females, adults and children? The above equation applies to adults, but we know that children and adolescents actually require a positive imbalance for healthy growth - what is not known is what degree of positive imbalance is healthy.This thesis is particularly concerned with energy-balance and imbalance during puberty, at which time the human body goes through extreme changes. We investigate how these changes are measured, and how energy-imbalance and themodelling thereof must change across this time. We will show that the proportions of children who are overweight and obese are higher than we would expect; commonly used models for body composition are not in agreement; commonly usedmodels for resting energy expenditure are not in agreement; children do not need a high energy-imbalance for normal growth; and those girls with early menarche are more likely to become overweight than their counterparts.