Obesity is a complex disease that greatly increases the risk of disease including diabetes, cardiovascular disease and certain cancers. Non-surgical weight loss is the first line of therapy for weight loss; however, many people struggle to lose weight loss and keep it off. There are strong connections between obesity and stress. Elevated levels of the stress hormone cortisol share several clinical metabolic and cardiovascular outcomes that are also apparent with obesity. It is well known that cortisol promotes cravings for sweet fatty foods, fat accumulation around the stomach region. For these reasons cortisol may play a key role in weight loss success. No studies have critically evaluated the relationship between stress and weight in obese population. Whilst salivary cortisol is a common technique used to diagnose Cushings Syndrome; a condition characterized by chronically elevated cortisol levels; few studies have validated this method in obesity.
Therefore, this study aims to investigate the relationship between stress and weight in lean and obese individuals through assessing salivary cortisol levels throughout the day and correlating with a range of metabolic parameters including body mass index (BMI), waist circumference, body composition, metabolic rate, stress and disease risk. Cortisol follows a diurnal pattern, with highest levels in the morning and lowest levels in the evening; therefore, we measured salivary cortisol at various time-points over multiple days. We find that obese appear to have greater variation in salivary cortisol compared to lean individuals, and this is associated with higher anxiety and perceived stress rather than fatness. We find whilst morning cortisol correlates with BMI, waist circumference, and fat mass, evening cortisol does not. These studies demonstrate the requirement of taking multiple samples to assess cortisol metabolism in obesity. Future studies will investigate the relationship between cortisol and non-surgical weight loss success.