Abstract
Increased adiposity is often associated with over activation of the hypothalamo-pituitary adrenal axis (HPA axis) and the sympatho-adrenal medullary system (SAM system) and excessive activation of these pathways in response to physiological challenges may be linked with the development of diseases. We tested the hypothesis that overweight/obese men aged 50–70 years will have greater HPA axis and SAM system responses to food intake compared with age matched lean men. Lean (Body Mass Index; BMI = 20-25 kg/m2; n = 19) and overweight/obese (BMI = 27-35 kg/m2; n = 17) men (50–70 years) made their own lunch using standardised ingredients at 1200 h. Concentrations of cortisol and alpha amylase were measured in saliva samples collected every 15 min from 1145 h-1400 h with the exception of during lunch (1215 h) where no sample was collected. Blood pressures and heart rate were measured at 1145 h and every 15 minutes between 1245 h and 1400 h. Overweight/obese men had significantly higher body weight, BMI, percentage body fat and waist and hip circumferences compared to lean men (p < 0.001 for all). The meal consumed by the participants consisted of 22% protein, 53% carbohydrates and 25% fat. Overweight/obese men responded to lunch with a significant increase in cortisol whereas lean men did not show such an increase (time*treatment p = 0.008). There were no significant differences between the groups in the salivary alpha amylase response to the meal (time*treatment p = 0.195) or in SBP, DBP, MAP or HR responses (time*treatment p = 0.726, 0.898, 0.713, 0.620, respectively). While men with a moderate level of overweight/obesity had a significant HPA axis response (as measured by salivary cortisol) to a standardised lunch, lean men had no HPA axis response. Lean and overweight/obese men had similar increases in SAM system activity (as measured by salivary alpha amylase) in response to the meal.
Highlights
Increased adiposity is often associated with over activation of the hypothalamo-pituitary adrenal axis (HPA axis) and the sympatho-adrenal medullary system (SAM system) and excessive activation of these pathways in response to physiological challenges may be linked with the development of diseases
Exposure to stress activates the SAM system and the HPA axis [1]
With the exception of heart rate, all of the SAM system parameters that were measured in the current experiment increased in response to lunch
Summary
Increased adiposity is often associated with over activation of the hypothalamo-pituitary adrenal axis (HPA axis) and the sympatho-adrenal medullary system (SAM system) and excessive activation of these pathways in response to physiological challenges may be linked with the development of diseases. Exposure to stress activates the SAM system (which results in increases in salivary alpha amylase, blood pressure and heart rate) and the HPA axis (which results in increases in salivary cortisol) [1]. Hyperactivity of these pathways can be associated with the development of numerous chronic conditions including cardiovascular disease, type 2 diabetes, anxiety and depression [2]. Animal studies by our research group as well as others suggest that obesity can be associated with increased HPA axis and SAM system responses to stress [4,5]. Others have suggested that there is no association between increased adiposity and stress pathway activation or that increased adiposity is associated with lower stress pathway activation to similar stressors [9,10,11]
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