The aims of this study were to describe a female obese population according to their food intake and physical activity, and to compare two methods to estimate physical activity (PA). The study included a nutritional interview where a detailed dietary history was done, an initial clinical day in which measurements of body composition and basal metabolic rate (BMR) were carried out and an estimation of PA by means of a triaxial accelerometer and a PA questionnaire. The group of volunteers showed a mean BMI of 37.15 kg/m2, a waist/hip ratio of 0.82 and a mean body fat mass of 43.34%. The average of BMR was 1720 Kcal/d and the CRNP of 0.79. The total caloric intake was 3344 Kcal/d with a energy-distribution of 43.1% Carbohydrates, 16.4% Proteins, 40.3% Lipids. Weight and BMI showed a positive correlation (p < 0.05) with the sedentary index (SI). Also, weight presented a positive correlation with the heart rate (p < 0.05). The estimates of PA derived from the questionnaire showed a positive correlation with the triaxial accelerometer (p < 0.01); and this one, revealed a negative correlation with the SI (p < 0.01). Anthropometric, metabolic and food intake variables are comparable to the results found in obese women from similar socioeconomic background. The estimates of PA according to the questionnaire were significantly correlated to the results of the triaxial accelerometer, thus confirming the validity of the questionnaire to assess PA in an obese population.