No effect of caloric restriction on salivary cortisol levels in overweight men and women.
OBJECTIVE
The effect of weight loss by diet or diet and exercise on salivary cortisol levels, a measure of hypothalamic pituitary adrenal activity, in overweight individuals is not known. The objective was to test the hypothesis that 24 weeks of moderate caloric restriction (CR) (25%) by diet or diet and aerobic exercise would alter morning and diurnal salivary cortisol levels.


DESIGN AND SETTING
Randomized control trial in an institutional research center.


PARTICIPANTS
Thirty-five overweight (BMI: 27.8±0.7 kg/m(2)) but otherwise healthy participants (16 M/19 F).


INTERVENTION
Participants were randomized to either calorie restriction (CR: 25% reduction in energy intake, n=12), calorie restriction+exercise (CR+EX: 12.5% reduction in energy intake+12.5% increase in exercise energy expenditure, n=12) or control (healthy weight-maintenance diet, n=11) for 6 months.


MAIN OUTCOME MEASURE
Salivary cortisol measured at 8:00, 8:30, 11:00, 11:30, 12:30, 13:00, 16:00 and 16:30. Morning cortisol was defined as the mean cortisol concentration at 08:00 and 08:30. Diurnal cortisol was calculated as the mean of the 8 cortisol measures across the day.


RESULTS
In the whole cohort, higher morning and diurnal cortisol levels were associated with impaired insulin sensitivity (morning: P=0.004, r(2)=0.24; diurnal: P=0.02, r(2)=0.15). Using mixed model analysis, there was no significant effect of group, time or sex on morning or diurnal cortisol levels.


CONCLUSION
A 10% weight loss with a 25% CR diet alone or with exercise did not impact morning or diurnal salivary cortisol levels.
['Tam|Charmaine S|CS|', 'Frost|Elizabeth A|EA|', 'Xie|Wenting|W|', 'Rood|Jennifer|J|', 'Ravussin|Eric|E|', 'Redman|Leanne M|LM|', '|||']
D000328:Adult D031204:Caloric Restriction D002940:Circadian Rhythm D004734:Energy Metabolism D015444:Exercise D005260:Female D006801:Humans D006854:Hydrocortisone D008297:Male D008875:Middle Aged D050177:Overweight D012463:Saliva D016896:Treatment Outcome D015431:Weight Loss
Cortisol Weight loss Hypothalamic pituitary adrenal CR BMI Calorie restriction Calorie restriction+exercise CR+EX Energy expenditure Insulin sensitivity ACTH AIRg Acute insulin response to glucose Adrenocorticotropic hormone Body Mass Index CALERIE EE ELISA Enzyme-linked immunosorbant assay HPA IGF Insulin-like growth factor LCD Low calorie diet Obesity PBRC Pennington Biomedical Research Center Si T3 T4 TSH The Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy Thyroid stimulating hormone Thyroxine Triiodothyronine VLCD Very low calorie diet.