Use of [14C]-sodium bicarbonate/urea to measure total energy expenditure in overweight men and women before and after low calorie diet induced weight loss.

expenditure (REE) and the thermic effect of a 2.7 MJ test meal (TEF) were measured at both weeks 0 and 10. At week 10 as compared to week 0, body weight decreased by 12.2 ± 1.6 kg (12.5%) ( P < 0.001). Total fat and lean mass decreased by 8.4 ± 1.0 kg (20.4%) and 3.8 ± 0.7 kg (6.7%), respectively ( P < 0.001). REE decreased by 500 ± 128 kJ/day (5.6 ± 1.3%) ( P < 0.002). Decreases in the TEE (0.18 ± 3.7%) and TEF (1.4 ± 0.9%) were not significant. In conclusion, although [ 14 C]-sodium bicarbonate/urea was well tolerated and di d not interfere with normal daily activities, it did not have suffi cient sensitivity to accurately measure weight loss induced changes in TEE in the range of 0.1-10%.