SEASONAL VARIATIONS IN ENERGY INTAKE, EXPENDITURE AND BODY COMPOSITION OF STUDENTS IN A NIGERIAN COLLEGE OF AGRICULTURE

Abstract

Studies were carried out using students of Federal College of Agriculture, Akure, Nigeria, on energy intake, energy expenditure and body composition. There were two groups of students - the longitudinal and the cross sectional groups. The longitudinal group participated in the three studies while the cross sectional group took part in two, that is energy intake and body composition studies. On the whole, 104 students participated in the experiments all aged between 18 and 30 years. Out of this number, 41 students took part in the longitudinal study while 63 took part in the cross sectional study. The three studies took place simultaneously in eight experiments covering a period of 19 months. The first study was on energy and dietary intake. The dietary survey methods used were 7-days weighed inventory and 24 -hour recall for the longitudinal and cross sectional groups respectively. Food samples were chemically analysed to determine nutrient content. It was found that both methods accurately estimated energy and nutrients intakes as the differences between them were not statistically significant (P>0.05). It was also found that foods collected at different seasons did not differ significantly in their nutrients content (P>0.05). Mean energy intake for the longitudinal group were 9.87 MJ (2362±146 Kcal/d) and 8.48 MJ (2028 ± 137 Kcal/day) for males and females respectively. Corresponding energy values for the cross-sectional group were 9.30 MJ (2225 Kca/d) and 8.14 MJ (1948 ± 29Kcal) for males and females respectively. For both males and females and in both groups, carbohydrate, fat and protein contributed about 75%, 13% and 12% respectively to the total energy intake. Moreover, the vegetable protein component of the total protein intake was over 70%. There were significant within individual and between group variations in energy intake in both sexes (P<0.05). Mean energy intake was significantly correlated with body weight (r=0.42) and body fat (r = 0.34) in males and highly correlated in females, (r m= 0.72) and (r= 0.77) for body weight and fat respectively. There were no significant differences in energy intake between the rainy and dry seasons in both sexes. Among the males, the influence of socio-economic background was also not significant (P>0.05). However, in the females socio-economic background significantly influenced their energy and nutrient intake. The second study was on energy expenditure and only the longitudinal group participated in this phase. Factorial method was used for the total energy expenditure (TEE). This method was validated against the intake-balance technique. In factorial method, Food and Agriculture Organisation/World Health Organisation/United Nation University (FAO/WHO/UNN (1985) prediction equations were used for estimating Basal metabolic rate (BMR) and energy cost values were obtained from Literature. The predicted mean BMR values ranged from 4.56 MJ (1091.35 ± 14.70 Kcal) to 6.75 MJ (1615.04 ± 64.99 Kcal) for the females and ranged from 6.08 MJ (1455.48 ± 11.48 Kcal) to 7.49 MJ (1793.03 ± 23.87 Kcal) for the males. Both BMR and BMR/kg body weight for males were significantly different from those of the females (P<0.05). However, when expressed per kilogram lean body mass (LBM), the differences were no longer significant. Mean TEE for males was 11.84 MJ (2832.93 ± 71.84 Kcal) and 9.47 MJ (2264.63 ± 72.52 Kcal) for females. The TEE and TEE/kg body weight were significantly different between males and females. The differences were removed when TEE was expressed per kilogram LBM. This showed that LBM was the major determinant in BMR and TEE. Energy expenditure was highly correlated with energy intake in both males (r = 0.72) and females (r = 0.94). Mean TEE was significantly different from the mean daily energy intake in both sexes. There were however, no significant seasonal variations in energy expenditure. The third study was on body composition. Anthropometric method was employed alongside the measurement of skinfold thicknesses. Skinfold thicknesses were measured at triceps, biceps, subscapular, breast, abdominal and suprailiac sites and, body weight and height were also determined. Mean height for the male longitudinal group was 172.31 ± 0.4 cm while that of the females was 161.16 ± 5.14 cm. Corresponding values for the cross-sectional group were 171.40 ± 5.97 cm and 163.59 ± 5.03 cm for males and females respectively. The mean body weights for the longitudinal group were 61.27 ± 1.28 kg and 57.64 ± 1.53 kg for males and females respectively. Corresponding values for the cross- sectional group were 59.29 ± 5.93 kg and 58.85 ± 7.12 kg for males and females respectively. Body weight correlated poorly with skinfold thicknesses in males (r = 0.21) while it correlated highly in females (r = 0.78). Total skinfold thicknesses were significantly higher in females than the males (P<0.05). Body mass index (BMI) were 20.63 and 22.13 for males and females respectively. This value for females was higher than what is desirable while that of the males was lower than the desirable value, using body scale index of British Fogarty Conference on Obesity of 1983. Mean optimum weights were 65.82 ± 74 kg and 57.55 ± 62 kg for males and females respectively using Mohr and Johnsen's (1974) formula. The values were 68.30 ± 0.31 kg and 59.11± 0.25 kg for male and females respectively when Ott 's formula (1963) was used. A different rapid method for determining optimum weight was devised from this research. It compared favourably with Ott's (1963) method but differs from Mohr's and Johnsen's (1972) method. Its ease of use makes it applicable to social and epidemiological researches. LBM contributed about 87% to the Total body weight in males and about 75% in females, thus exhibiting sexual dimorphism. About half of the females studied had relative weight more than 100% which means having body weight higher than what is optimally desirable. The males had normal body weight by Mohr's (1979) relative weight standards. However, by Jelliffe's (1966) standard, the males were within 90- 94% of the weight-for-height while the females were within 100 - 104%. There were no significant changes in body composition between the raining and dry seasons (P>0.05). There were however, significant differences in body composition between the upper socio-economic class and the lower socio-economic class. This is an indication that changes in body composition and energy intake are more of a reflection of the financial status of the individual than it is with seasonal influence.