Normal levels of energy expenditure in patients with reported "low metabolism'

The present study examined the hypothesis that patients with apparent diet-resistant obesity have subnormal energy expenditure. Ten biochemically euthyroid patients (eight women and two men), aged 21-76 years, with either excessive gynoid fat distribution or obesity (BMI 23.8-41.0), were referred to the department thought to be suffering from a low metabolic rate syndrome since dietary records showed very low energy intake (< 5 MJ day-1) in combination with failure to lose weight on low-energy diets. Twenty-four-hour energy expenditure (24-h EE), basal energy expenditure (BEE) and sleeping energy expenditure (SEE) were measured in a respiration chamber on a fixed activity programme. The patients consumed a diet containing 37 energy-per cent (E%) fat, 47 E% carbohydrate and 16 E% protein. The individual energy intake was estimated from a previously established algorithm between 24-h EE and fat-free mass (FFM) estimated by bioimpedance. Results were compared with equivalent values in a reference population of 76 subjects ranging from normal weight to obese. No evidence of low metabolism was found in terms of adjusted 24-h EE in the patients with diet resistance when compared with the control group (9263 +/- 819 kJ vs. 9211 +/- 558 kJ). No differences were found when comparing adjusted BEE and SEE in the two groups (7655 +/- 727 vs. 7411 +/- 770 kJ 24 h-1 and 7048 +/- 672 vs. 6911 +/- 408 kJ 24 h-1). The physical activity index (PAI) during the chamber stay was likewise within normal values (1.32 +/- 0.07 vs. 1.34 +/- 0.04; NS).