Proceedings of The Physiological Society
University of Oxford (2008) Proc Physiol Soc 12, C14 and PC24
Illness, body mass index and leptin
A. Taylor1, R. Baskerville2, L. M. Castell1
1. Nuffield Dept of Anaesthetics, University of Oxford, Oxford, United Kingdom. 2. 27 Beaumont Street, Oxford OX1 2NR, United Kingdom.
Introduction There is anecdotal evidence that obese individuals suffer from poor wound healing and frequent minor illnesses such as upper respiratory tract infections (URTI) cf. lean individuals. The altered metabolic, psychological and endocrine status of obesity may lead to immunodepression. Our group has investigated URTI in fatigued athletes and military personnel (Castell, 2003); one study focused on the obesity hormone, leptin which regulates energy balance, and its role in immune function. Decreased circulating leptin can lead to hyperphagia in some genetically obese individuals (O’Rahilly, 2002). However, human obesity is usually characterized by excessive leptin, rather than deficiency. The leptin functional receptor is found in all immune response cell types: thus leptin may link nutritional status, energy balance and immune function. Sleep loss, partial or chronic, is linked to decreased immune function. Obesity is a factor in obstructive sleep apnoea, which significantly reduces sleep duration and quality. Aims This pilot study surveyed the incidence and severity of URTI, psychological and sleep profiles in sedentary participants of different ages, and body mass indices (BMI). The aim was to observe whether mild obesity (BMI 30-35) predisposed people to an increase in URTI cf. individuals with a lower BMI. The survey was a precursor to a more detailed study. Methods Eight lean, 2 overweight, 8 obese sex matched, sedentary participants were recruited for this ethically approved survey. Anthropometrics (ht, wt, waist, hips) were taken; A resting blood sample measured plasma leptin; Daily questionnaires were given for 6 wks to monitor URTI; POMS (depression, stress, fatigue, motivation); Sleep (duration, quality); Dietary diaries. A multiple regression General Linear Model was used to explain the “illness score”. Results A higher BMI was significantly associated with higher symptoms of illness (p<0.01). Calorie consumption was associated with BMI (p<0.05). BMI correlated with plasma leptin concentration. Poor sleep quality predisposed individuals to an increase in URTI symptoms (p<0.032); in addition it was associated with higher levels of depression (p<0.005) and stress (p<0.005). Sleep duration did not have any effects. There was an apparent link between smoking and increased URTI symptoms. Discussion The study showed links between increased BMI, poor sleep quality and the incidence of self-reported URTI. It is suggested that obesity is associated with an increase in URTI cf. normal or lean weight. BMI was linked with blood leptin concentration, and it is tempting to speculate that there might be a link between leptin and increased URTI.
Where applicable, experiments conform with Society ethical requirements