A study of the prognostic respiratory markers of sustained weight loss in obese subjects after 28 days on VLCD

Abstract

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% (FFM_TBIA) and 8.9% (FFM_NB), 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.