The areca nut is chewed by many of the world's population, mainly in South and Southeast Asia. Anthropometric data for 458 Sarawaki adults aged over 24 years, measured both in 1990 and in 1996, were examined in relation to use of tobacco and areca nut. Compared to non-smokers, smoking men were significantly taller and slightly (not significantly) thinner in both years, while smoking women were thinner in 1990 and slightly (not significantly) thinner in 1996. In both sexes there was an increase in the mean and range of body mass index (BMI, W/H2) over the 6-year interval. Smoking women showed a significantly smaller increment in BMI after allowing for areca nut use, which was associated with a similar trend, and this finding depended on including areca use in the model. The trend for men was similar. Possible effects of areca use could reflect variation in 'affluence' or conservatism, or appetite suppression. However, resting metabolic rate in 54 men and 70 women aged 24-60 years was associated with areca use. This association appeared to be mediated by the maximum room temperature of the 24 h preceding measurement. In women, a significant curvilinear association of RMR with maximum temperature was found in users of areca nut but not in non-users. In men, RMR was 7% higher (p < 0.05) in users of areca nut than in non-users, after allowing for age, height, weight, the sum of four skinfold thicknesses, and haemoglobin, but the association with maximum temperature was similar in both groups. It is speculated that constituents of areca nut modulate thermoregulatory pathways, resulting in prolonged temperature-dependent and hyperthermic heat production in this population; that males are more responsive to this effect than females; and that by this mechanism, and possibly also through centrally mediated effects on appetite for food, areca use could contribute to long-term variation in energy balance represented by change in BMI.
The effects of population pressure on agricultural sustainability in the delicate tropical and subtropical ecosystems have often been thought to explain high prevalence rates of malnutrition in rural South-East Asia. However, recent studies in rural Sarawak suggest that processes of modernisation have resulted in increased variations in energy nutritional status in adults. A contributory factor may be consumption of the areca nut (Malay pinang, of the palm Areca catechu). This is thought to influence energy balance through effects on appetite and resting metabolic rate. Body mass index (BMI, kg/m2) data for 325 Iban men and 438 non-pregnant Iban women, measured in 1990 and again in 1996, have been analysed in relation to areca use, smoking behaviour, socio-economic status, and reported morbidity. Body composition derived from skinfold thickness measurements for 313 men and 382 women was also analysed. The results suggest that use of areca nut is associated with significantly lower age-related increments in BMI and percentage body fat in women after allowing for age, smoking, reported morbidity, and confounding socio-economic factors. Therefore, the impact of recent economic and social development seen in rising prevalences of 'over-nutrition' may be modulated by use of the areca nut.