| Abstract: | We investigated the thermic effect of feeding (TEF) equicaloric (1004.16 kJ) portions of randomly provided fresh squeezed orange juice (17.45 oz) and Protein RushTM (40g protein, 17 oz). Eight subjects (5 women, 3 men; 25.8 ± 9.2 yrs, 174.9 ± 12.4 cm, 71.5 ± 17.5 kg) reported to the lab on subsequent mornings and underwent 30-minutes of resting metabolic rate testing, followed by 2-minutes of drink ingestion, followed by 60-minutes of supine rest. Data were collected via a metabolic cart and ventilated hood. Resting data were subtracted from all post-ingestion measures. Within groups the rate of O2 uptake (l min-1) increased significantly for protein (+29%, p = 0.03) but not for orange juice (+21%, p = 0.11); when expressed as ml . kg-1 min-1, both groups had significant increases (p < 0.005). Between groups O2 uptake measurements over the 1-hour period revealed a 21% difference between orange juice (2.66 ± 0.6 liters) and protein (3.36 ± 0.9 liters) that did not reach statistical significance (p = 0.10). Energy expenditure (kJ) determined via the respiratory exchange ratio (RER) revealed orange juice at (60.8 ± 10.1 kJ) and protein (63.7 ± 20.0 kJ) were 5% different, also non-significant (p = 0.72). The RER averaged over the 60-min TEF period was significantly different between orange juice (0.868 ± 0.07) and protein (0.773 ± 0.04) (p = 0.005). Sample size calculations indicate that 14 subjects would reveal statistical significance for O2 uptake yet 163 subjects would be required for energy expenditure differences between drinks. We suggest the potential for bias in selecting a measure of TEF from data within- and between-groups and, O2 uptake vs. energy expenditure. |
