ANNALS OF HUMAN BIOLOGY, 1991, VOL. 18, NO. 3,245-251

Basal metabolic rate and physique of Gurkha and British soldiers stationed in Britain

S. J. ULIJASZEKI- and S. S. STRICKLAND$

tDepartment of Biological Anthropology, University of Cambridge, UK $Centre for Human Nutrition, Department of Public Health and Policy,

London School of Hygiene and Tropical Medicine; and Department of Anthropology, University College, London, UK

Received 8 September 1989; revised3 October 1990

Summary. Measurements of basal metabolic rate (BMR) and physique were made on Gurkha soldiers stationed in Britain, and on British controls matched by body weight and occupational background. Gurkhas were significantly shorter, with greater body mass index, calf circumference and subscapular skinfold thickness than the European controls, although there was no difference in BMR between the two groups. For the Gurkhas, linear regression analysis incorporating factors which may influence BMR showed a positive relationship between the length of time since leaving Nepal and BMR, supporting the view that Asians living in temperate regions have higher BMR than those living in the tropics.

1. Introduction It has been argued that inter-population variation in basal metabolic rate (BMR)

not due to differences in body size and composition is a function of climatic rather than ethnic variation (Soares and Shetty 1988). Although earlier proposals for the estimation of energy requirements have commented on the putative effect of climate on BMR (FAO 1950, FAO/WHO 1973), the current proposals (FAO/WHO/UNU 1985) do not. Differences in body composition are believed to account for the vast majority of observed variation in BMR within populations (Durnin 1981), and variation in body weight has been shown to explain over 60°7o of the variation in BMR of Indian subjects (Soares and Shetty 1988). In this study, however, the BMRs of subjects from urban upper socioeconomic groups are about 6°7o lower than the values predicted by the Schofield (1985) equation on the basis of body weight. This difference is attributed, without verification, to climatic and environmental factors (Soares and Shetty 1988).

In the present study, BMR and anthropometry of well-nourished adult Nepali males (Gurkha soldiers stationed in Britain) are compared with similar measurements made on British controls (members of the Parachute Regiment) matched by body weight, to examine possible ethnic differences in BMR. Possible climatic effects on the BMR of the Gurkhas are examined using multiple linear regression analysis of BMR against anthropometric variables and time since leaving Nepal.

2. Subjects and methods The subjects of this study were from one of the Gurkha regiments of the 5th

Airborne Brigade stationed at Aldershot, UK. Twenty fit, healthy individuals were selected randomly for each quartile of body mass index (BMI) from a group of 50. British controls, also from the 5th Airborne Brigade, were selected to match the Gurkhas by body weight (plus or minus 1 kg). Three subjects could not be adequately matched, and their data were excluded from the matched-pairs analysis but included in the subsequent analysis of climatic effect using multiple regression. All Gurkhas were from the same ethnic group, the Gurung, from the West Central Region of Nepal. All

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246 S. J. Ulijaszek and S. S. Strickland

subjects were aged between 18 and 33 years. BMR was measured for 15 min on waking in bed, between 04.30 and 07.00, after 11 h fast.

Oxylog portable oxygen consumption meters modified for low flow rates were used (McNeill, Cox and Rivers 1987a), calibration of flow rates being carried out by passing room air at different rates of known constant flow through the equipment. The relationship between the flow measured by the Oxylog and that measured by Chell and Hastings mass flow meters respectively, was linear and almost identical to that obtained by McNeill et al. (1987a). Correction factors of 1.047 and 0" 947 were incorporated into the calculation of oxygen consumption (McNeill et al. 1987a) for the two Oxylogs. These two pieces of equipment had mean percentage errors of measurement of 2- 0 and 2- 7 respectively. Values for oxygen uptake were derived as the mean of the final 5 min of BMR measurement. Anthropometry was carried out by one trained observer (S.U.), using methods described in Weiner and Lourie (1981). Fat-free mass (FFM) was calculated by subtracting the proportion of body weight as fat, from total body weight. Percentage of body weight as fat was calculated from the sum of four skinfold thicknesses (biceps, triceps, subscapular and suprailiac) using the formula of Durnin and Womersley (1974), in conjunction with the Siri equation (Siri 1956).

Comparisons between the two matched-paired groups were carried out using paired t-tests. None of the anthropometric data, including skinfold thicknesses, were significantly skewed and logarithmic transformations of skinfold thickness data (Edwards, Hammond, Healy, Tanner and Whitehouse 1955) were not used in analysis. Possible effects of climate on BMR were examined by including the length of time since leaving Nepal at the time of measurement (T(Nep))(months) in linear regression analysis of factors influencing BMR, for all 20 Gurkha volunteers.

3. Results Table 1 gives mean values for age, anthropometric variables and BMR for the

Gurkhas and their European controls. Although matched for body weight, Gurkhas are significantly shorter (t=3-75, p<0-01), with greater BMI (t=4.01, p <0-001), calf circumference (t= 6-90, p <0.001) and subscapular skinfold thickness (t= 2.28,

Table 1. Physical characteristics and BMRs.

Gurkha British (n = 17) (n = 17)

Mean SD Mean SD Paired t-test

Age (years) 25.1 Weight (kg) 67.1 Height (cm) 166.8 BMI (kg m) 24.1 Arm circumference (cm) 27-6 Calf circumference (cm) 37- 4 Skinfold thicknesses

Biceps (mm) 5" 0 Triceps (mm) 8.8 Subscapular (mm) 11.2 Suprailiac (mm) 13.3 Medial calf (mm) 5.9

BMR (M J/day) 7.05 BMR (KJ/kg per day) 105.1 BMR (KJ/kg FFm per day 124.1

3 "0 22"9 3" 1 2-01 4"6 66"8 4.6 1"02 3"8 173" 1 6"3 3-75** 1 "4 22-3 1 "7 4"01"** 1 "4 27"7 1 "7 0"05 2"0 35"3 1 "7 6"90***

1-7 4"0 1"0 2"10 2-5 7"9 2"8 1 "04 3-6 8"9 2"2 2"28* 5"3 11"0 3"5 1"62 1"5 7-4 3"1 1"61 0"93 7"29 1 "25 0"68

12"2 109"8 21-4 0"82 13"9 126"4 25"0 0.88

* p < O ' 0 5 ; **p<O'O1; ***p<O'O01.

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248 S.J. Ulijaszek and S. S. Strickland

p < 0.05) than the European controls. There are no significant differences in BMR between these two groups, however.

The relationship between BMR/kg body weight and T(Nep) was found to be nonlinear (figure 1), a log(e) transformation making this relationship linear (y = 5" 35 + 0" 66x, n = 20, r = 0- 54, p = 0" 014). The log(e) t ransformation of T(Nep) (log T(Nep)) was then used in the linear regression analyses.

Table 2 gives the results of regression analyses of various factors influencing BMR. Log T(Nep) explains 29% of the variance in BMR in the Gurkhas, with FFM explaining only an additional 5%. Weight alone explains only 4% of the variance in BMR.

4 . D i s c u s s i o n

Gurkha soldiers stationed in Britain show no difference in BMR from European controls matched for body weight. This supports the view that ethnic differences in themselves may have no effect on BMR (Durnin 1981). It is less clear, however, whether climatic factors affect BMR or not. The effect of log T(Nep) on BMR shown in table 2 may be due to chance, since the sample size is small and there is considerable variability in observed BMR. If the effect is real, there are problems with the interpretation of the results. I f the Gurkhas are a mixed group with different recent environmental experiences contributing to differences in BMR, then it would be expected that their BMRs would be more variable than those of the British controls. This is not the case. The inter-individual coefficient of variation (CV) for BMR of the Gurkhas is similar to those found in two studies from India (CV = 13.2%, Gurkha; CV = 11.7 %, Soares and Shetty 1988; CV = 12.7 %, McNeill, Rivers, Payne, Britto and Abel 1987b), whilst the CV for BMR of the British controls is similar to that of healthy male graduate students at Oxford Polytechnic (CV= 17.1%, British controls; C V = 15.2%, Henry, Hayter and Rees 1989). For both the Gurkha and British groups, CV of BMR/kg and BMR/kg FFM is no lower than that of BMR, however, suggesting that inter-individual variability of BMR within each of these two groups is not due to differences in body composition.

It is possible that inter-individual differences in the level of training may explain part or all of the difference in BMR variability between the Gurkhas and the British. It has been argued that highly trained men have a higher resting metabolic rate than moderately trained or untrained men, even when the measurements are adjusted for their metabolic size (Poehlman, Melby, Badylak and Calles 1989); the Gurkhas may be more homogeneous with respect to the amount of effort that they put into their physical exercise than the British controls. Further, anecdotal evidence suggests that the level o f physical activity of Nepalis in the British army is greater than that of Nepalis living in the village. It is therefore possible that the observed effect of greater BMR with longer

Table 2. Regression analysis of factors influencing BMR of Gurkhas.

Dependent variable: BMR (M J/day)

Independent variable Multiple r r 2 d.f. F

Weight 0.19 0-04 1 .18 0-66 FFM 0.28 0-08 1 .18 1.55 Duration a 0-54 0"29 1 .18 7.33* Duration a + FFM 0- 58 0" 34 2" 17 4" 30* Duration a + FFM + weight 0- 61 0" 37 3" 16 3" 11

a Duration: 1Ogl0 (time since leaving Nepal). * p<0-05.

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T(Nep) may be a function of increased training on joining the army, although this remains to be tested.

BMR/day is 3.4% greater in the British controls than in the Gurkhas, whereas BMR/kgFFM is only 1-9% greater. This residual difference may reflect small differences in body composition which could not be picked up with the method used for estimating FFM in this study, and/or real differences in the BMR of the Gurkhas, due to climate or training. It is unlikely that these differences are the result of methodological bias, since the same methodology was used throughout. Comparison of measured BMRs with those predicted from body weight using the appropriate Schofield (1985) equation gave good agreement for both the Gurkhas and the British, however, suggesting that any bias in measurement due to methodology was small.

In addition to climate, dietary factors and baseline thyroid hormone status could be responsible for the relationship between log T(Nep) and BMR observed this study. Although there is no doubt that severe dietary energy deficiency and reduced thyroid hormone levels are associated with a reduced resting metabolic rate (Millward 1986), the Gurkhas of this study were not undernourished. Prior to posting to Britain, new recruits may spend several months in a British army camp where they are 'built up', on a regime of hard physical training and an army diet not known for its meagre portions or low energy density. Although there are no data on the thyroid hormone status of the subjects of this study, the Himalayas are a region of endemic goitre (Ward, Milledge and West 1989), where the prevalence of this condition in the western and central regions varied from 32% to 57% in 1985 (Acharya 1987). It is not clear to what extent the adoption of a British army diet would result in improved thyroid hormone status and an associated increase in BMR, however. Increased iodine availability from the diet results in a fairly rapid response in the production of thyroid hormones (Hetzel 1987), and any change in BMR due to this factor is likely to have already taken place in the subjects prior to this study.

The observed relationship between log T(Nep) and BMR could be due to level of training, or to acclimatization. Most arguments for (QuenouiUe, Boyne, Fisher and Leitch 1951, Henry, Pigott and Emery 1987, Soares and Shetty 1988) and against (Durnin 1981, Lawrence, Thongprasert and Durnin 1988) a climatic effect on BMR have been based on cross-sectional data. However, in a longitudinal study of Japanese subjects, Suzuky (1959) reported a significant seasonal fluctuation in BMR which is closely related to average temperature. Further, in a study in which the effect on BMR of moving from a tropical to a temperate climate or vice-versa was measured, an average change of about 8% of the baseline value was reported (Mason and Jacob 1972). Confirmation of either a climatic or training effect on the BMR of Nepalis enlisting into the British army also requires longitudinal study.

Acknowledgements The authors gratefully acknowledge the cooperation of volunteers from the 6th

Queen Elizabeth's Own Gurkha Rifles and the 23rd Parachute Field Ambulance of the 5th Airborne Brigade, and their Commanding Officers Lieutenant Colonel J.A. Anderson and Lieutenant Colonel L.P. Lillywhite. They also thank Dr Chris Gooderson and Dr Andrew Duggan of the Army Personnel Research Establishment for advice and logistical support, and Professor P.R. Payne, Ms M. Griffiths and Professor G.W. Lasker for helpful comments. They also thank Malcolm Cox, Jim Vinter, and Dr I.A. MacDonald for technical assistance. The authors gratefully acknowledge the support of the Ministry of Defence during this study.

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Zusammenfassang. An Gurkha Soldaten, die in Grol3britannien stationiert sind, sowie an einer hinsichtlich Gewicht und Beruf entsprechenden britischen Vergleichsstichprobe, wurden der KOrperbau erfal3t und Messungen der basalen Stoffwechselrate (BMR) durchgeftihrt. Gurkhas waren signifikant kleiner und hatten einen gr613eren KOrpermassenindex, einen grOBeren Wadenumfang sowie eine grOflere

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subskapulare Hautfaltendicke als die europ~ische Kontrollstichprobe, w~ihrend in der BMR kein Unterschied zwischen beiden Gruppen beobachtet werden konnte. Eine lineare Regressionsanalyse, die Faktoren bert~cksichtigte, welche einen EinfluB auf die BMR ausiaben kOnnten, ergab for die Gurkhas einen positiven Zusammenhang zwischen der BMR und dem vergangenen Zeitinterval seit dem Verlassen Nepals. Dies belegt die Ansicht, dab Asiaten, die in gem~Bigten Klimaregionen leben, eine hOhere BMR aufweisen als solche, die in den Tropen leben.

R6sumcL On a mesur6 le taux du m6tabolisme de base (BMR) ainsi que le physique, de soldats Gurkha stationn6s en Grande-Bretagne et de contr61es britanniques qui leurs sont harmonis6s pour le poids corporel et le contexte professionnel. Les Gurkha sont significativement plus petits, avec un indice de masse corporelle, un p6rim6tre du mollet et un pli-cutan6 sous-scapulaire, plus petits que ceux des contr61es europ6ens, bien qu'il n'apparaisse pas de diff6rence de BMR entre les deux groupes. Pour les Gurkha, une analyse de r6gression lib6aire incorporant les facteurs qui sont susceptibles d'influencer le BMR, a montr6 une association positive entre BMR et dur6e de s6jour hors du N6pal, en accord avec l'id6e que les asiatiques vivant dans les r6gions temp6r6es ont un BMR plus 61ev6 que ceux qui vivent sous les tropiques.

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