Seasonal fluctuation in energy balance among farmers in Northeast Thailand: The lack of response of energy intake to the change of energy expenditure

The study aimed to clarify the seasonal fluctuations in energy balance and their factors among rice-growing farmers in Northeast Thailand whose rice production was enough to their food energy demand.Prospective and repeated measurements in the field.A rain-fed rice-farming village.Eight pairs of husband and wife.In each of four periods in a year, anthropometry, energy expenditure survey with heart-rate monitoring and minute-by-minute activity recording, and food consumption survey were conducted for each subject for 4 days.The change of body weight was modest but differed significantly (P0.001) between pre-harvest and post-harvest seasons: 1.3 kg (2.3%) for males, 2.5 kg (4.3%) for females. Total energy expenditure (TEE) fluctuated markedly between the 4 seasons (P0.001 for males and females), but total energy intake (TEI) fluctuated to lesser extents (P0.05 for females only). In relation to energy expenditure, physiological indicators (except respiratory quotient) did not fluctuate throughout the year but behavioral indicators did. The changes in body weight were significantly correlated with the changes in TEE (r = 0.60, P0.05 for males; r = 0.83, P0.01 for females) but not with the changes in TEI; TEE and TEI were not correlated.The modest seasonal changes in body weight among rain-fed rice farmers in Northeast Thailand were caused by the lack of response of TEI to the change of TEE.