Basal metabolic rate (BMR) of 15 healthy male adult Papua New Guinea highlanders who live on a sweet-potato staple diet were examined by the indirect energy metabolims measuring method from October to December in both 1980 and 1982.
In experment 1, 5 subjects followed a rice diet (RD) for 13 days and then switched to a low-protein rice diet (LPRD) for another 13 days. Mean RMR in the last 2-3 days of each diet period was 22.1±2.7 and 21.2±1.4 kcal/kg body weight/day (35.1±4.1 and 33.6±2.6 kcal/m²/hr), respectively.
In experiment 2, 5 subjects followed a sweet-potato diet (S-PD) for 14 days and then switched to a low-protein sweet-potato diet (LPS-PD) for another 14 days. Mean BMR in the last 2-3 days of each diet period was 21.2±1.9 and 22.1±1.6 kcal/kg body weight/day (32.3±2.3 and 33.3±2.2 kcal/m²/hr), respectively.
In experiment 3, 5 subjects were fed with a protein-free diet (PFD) for 11 days. Mean BMR in the last 2-3 days of this period was 25.3±2.2 kcal/kg body weight/day (38.3±4.0 kcal/m²/hr).
Mean BMR measured within 2-3 days following the start of each of experiments 1, 2 and 3 was 24.7±2.3 kcal/kg body weight/day (38.0±3.3 kcal/m²/hr) in all subjects (15 persons) . We considered this value to be their usual BMR (control) .
The subjects apparently followed a diet of similar content to the sweet-potato diet before the start of this experiment, but mean BMR of the S-PD group was significantly lower than the control value.
On the oter hand, mean BMR of the RD and PFD groups, having a higher protein intake than obtained from their usual diet, was similar to the control value. We thought from the above results that protein intake levels do not influence BMR, although no clear explanation could be found for the results.
In addition, we found that the Papua New Guinea highlanders showed high respiratory quotients (0.91-0.99) under such BMR measurement conditions, and we discussed this finding.