The aim of this study was to quantify the impact of obesity class on Health-Related Quality Of Life (HRQOL) and Total daily Energy Expenditure (TEE). 69 obese individuals were self-selected to 1 of 3 groups based upon Body Mass Index (BMI). Anthropometric parameters (height, weight, waist and hip circumference, fat mass, lean body mass), biological parameters (high density lipoprotein, low density lipoprotein, triglycerides, glycaemia, total cholesterol), and resting energy expenditure were assessed for each group. The Short Form Health Survey (SF-36) questionnaire and Hospital Anxiety Depression (HAD) scale were used to measure HRQOL, and TEE was estimated by Kurpad's method. Class 3 obesity was associated with greater impairment of the physical aspects of the SF-36 (37.2±11.3), greater depression risk (8.2±4.1), and higher TEE (30.0±7.9 Kcal·day (-1)·kg (-1)) than the lower obesity classes. No difference was observed among the 3 groups in the mental and psychosocial aspects of HRQOL. Impaired physical functioning was correlated with fat mass, age, waist circumference, glycaemia control and bodily pain. TEE was positively correlated with BMI, weight, fat mass and lean body mass. The obesity class had a negative impact on the physical health aspect of HRQOL, depression risk and energy expenditure. These impairments were associated with excess fat mass, waist circumference and glycaemia parameters.