Evaluation of the Metabolic Indicators in Obese Diabetic Patients: A Case-Control Study

Abstract

Measurement of the energy expenditure in man is a key step in the calculation of the energy requirements that are needed for clinical nutritional assessment and body weight management. Obese diabetic patients suffer from variable metabolic abnormalities that are associated with insulin resistance. The respiratory quotient (RQ) is an important metabolic indicator. It is the ratio of carbon dioxide produced to oxygen consumed at the cellular level; however, when it is calculated from expired gasses, it is referred to as the respiratory exchange ratio (RER). Under steady conditions, the RER provides a precise estimate of the RQ. On a mixed diet, part of the total CO2 produced and O2 consumed by the cells comes from metabolism of carbohydrates (RQ= 1.0), and proteins (RQ= 0.82) in addition to fats (RQ= 0.71). In general, the RQ varies between 0.7 to 1.1 depending on the proportion of substrates being metabolized and the rate of ventilation [1]. When the value of the RER is high, oxygen consumption is lesser than required, and anaerobic metabolism is taking place, e.g. during high-intensity exercise. It is worth noting that, RER excludes protein metabolism, which during rest is assumed to be very minimal. Many factors affect the value of the RQ and accordingly cause changes in the metabolic rate. Previous studies showed ethnic variation with the Africans having higher RQ and lower resting metabolic rate (RMR) compared to the European subjects [2,3]. The high RQ indicates that the carbohydrate is utilized as the primary source of energy and this is a recognized cause of weight gain.