Objective: To investigate parameters of energy metabolism during a 28 d VLCD to identify possible prognostic markers of weight change observed, subsequently, when the subjects were on a six-month hypocaloric diet.
Design: Longitudinal, clinical intervention study of a 2 MJ diet daily for 28 d and six month follow-up under a conventional, hypocaloric diet.
Subjects: Seven pre-menopausal women and one male all morbidly obese but otherwise healthy (age: 16-47 y, BMI 38.9-50.5 kg/m2).
Measurements: Body weight, resting energy expenditure (REE), resting respiratory quotient (RQ) and the 5 h thermic effect of food (TEF) were assessed by indirect calorimetry at the beginning and at the end of a 28 d VLCD treatment. Body composition was measured on day 1 by hydrodensitometry and tetrapolar bioelectrical impedance (TBIA), on day 28 by TBIA and nitrogen balance (NB) and by TBIA on follow-up.
Results: The individual weight loss during VLCD (mean 9.9 +/- 2.4 kg) was significant (P < 0.01) and correlated significantly with energy deficit (r = 0.83, P = 0.01). REE/FFM decreased 6.2% (FFMTBIA) and 8.9% (FFMNB), respectively. TEF28 was unchanged from TEF1 while fasting RQ declined during the intervention period but was back to baseline already within one month of follow-up even though the mean weight loss at six months had increased to 14.0 +/- 5.6 kg. There was a significant (P < 0.05) positive correlation between RQ28 and body-weight changes after one, three and six months of follow-up. The RQ28 explained 60-72% of the inter-individual variation in weight change.
Conclusion: The resting RQ measurement is recommended as a simple and inexpensive assessment at the end of a strict weight-loss regimen in order to identify those individuals who may need greater assistance in maintaining a weight-loss when placed on a subsequent, free-living hypocaloric diet.