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Karagiannis, Nick (2008) A study on human leanness: assessing variability of self-reported oral consumption in relation to physiological and metabolic indices. Masters thesis, London Metropolitan University.
Lean individuals who apparently possess mechanisms to resist obesity have been understudied compared to the research directed in the study of obesity. The few studies on leanness classified subjects into "small" and "large" eaters, by selecting them from a greater number of participants, based on self-reported consumption alone. 40 lean male and female individuals, with BMI below 22 kg/m2, were recruited for this study. The subjects exhibited great variability in self-reported energy (Range: 795 - 3976 kcal/day) and fat (Range: 16 - 194 g/day) intakes. Due to the small number of participants, a technique was used to classify them into "small" and "large" eaters, based on self-reported energy and fat intakes. However, this proved to be inadequate. Various physiological and metabolic indices related to energy metabolism were assessed to investigate the variability in the subject's self-reported oral intake. Body fatness was measured with the use of air displacement plethysmography. Skeletal muscle mass was quantified utilizing urinary creatinine excretion. The 24 hour urine samples were also used for the quantification of catecholamines excreted. The muscle fibres of the non-dominant vastus lateralis were quantified into type I and II, utilising a non-invasive technique. Finally, indirect calorimetry and heart rate monitoring were utilised to assess metabolic rate (REE), fat oxidation and resting heart rate, both post-absorbedly and postprandially, following the consumption of a high fat drink. Male subjects showed an inverse relationship between BMI and both energy and fat intakes, while fat mass formed an inverse relationship with fat intake. Energy intake presented a positive relationship with REE corrected for body mass and for fat-free mass in males and resting l1eart rate and REE corrected for body mass in females. Fat intake correlated positively with REE and REE corrected for body mass and for FFM in males and REE corrected for body mass and resting heart rate in females. All subjects showed a significant increase in lipid oxidation rate after the consumption of the high fat drink. However, most of the significant correlations identified were rejected after correction factors for multiple correlations were applied. Recruiting a greater number of subjects and utilizing more invasive and accurate techniques, the current study would have produced stronger results.
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