Impact of body weight loss, body fat distribution and the nutritional status on the cortisol response to the Trier Social Stress Test (TSST) was investigated in this study. Fifty-one men (17 non-obese, 20 abdominally obese and 14 reduced obese) and 28 women (12 non-obese, 10 peripherally obese and 6 reduced obese) were subjected to the TSST in fed and fasted states. The TSST response was determined using salivary cortisol measurements. The nutritional status (being fed or fasted) had no effect on the cortisol levels during and following the TSST. Reduced obese men exhibited lower cortisol levels than non-obese men. Cortisol levels in obese men were not different from those of non-obese and reduced obese subjects. In women, there was no significant difference between groups. These finding suggest that weight status in men influences cortisol reactivity to a psychological stress and the different responses seen among genders could be linked to the different fat distributions that characterize men and women.
In humans, high levels of glucocorticoids have been reported to promote the deposition of abdominally located visceral fat and its associated metabolic alterations (Björntorp, 1993, Björntorp, 2001, Chalew et al., 1995, Drapeau et al., 2003, Epel et al., 2001, Marin et al., 1992 and Pasquali and Vicennati, 2000). One of the most acknowledged examples of the link existing between hypercortisolemia and abdominal (visceral) obesity is the Cushing's syndrome patient, in whom normalization of cortisol levels is followed by a decrease in visceral fat (Peeke and Chrousos, 1995 and Rebuffe-Scrive et al., 1988). In addition, psychological and socioeconomic factors leading to sustained HPA axis activation have also been shown to promote visceral obesity (Larsson et al., 1989, Rosmond and Björntorp, 1999, Rosmond and Björntorp, 2000 and Wing et al., 1991). In male cynomolgus monkeys, social stress-induced hypercortisolemia leads to the deposition of intra-abdominal adipose tissue (Jayo et al., 1993). Similarly, in dominated cynomolgus monkeys, social subordination, which stimulates HPA axis, is also strongly associated with a preferential deposition of visceral fat (Shively et al., 1997).
Increase in the HPA axis activity seems to not only be a source of visceral obesity but may also be a consequence of excessive deposition of abdominal fat, which has the capacity to release cytokines stimulating the HPA axis (Mastorakos et al., 1993 and Yudkin et al., 1999). We indeed recently demonstrated that a reduction in waist circumference in men could reduce the awakening cortisol response (ACR) (Therrien et al., 2007), which is used to assess the HPA axis function (Fries et al., 2009 and Schmidt-Reinwald et al., 1999). The proposition that visceral fat can stimulate the cortisol secretion to stress based on ACR needs to be further substantiated, using other types of stress such as the one we propose in the present study.
The observation that visceral fat loss can reduce the activity of the HPA axis contrasts with findings demonstrating that weight loss and associated behaviors restricting energy intake increase HPA axis activity. In laboratory animals, weight loss and fasting are associated with a HPA axis activation that has been demonstrated to be rather extreme in the obese Zucker rat, in which fasting may represent a psychogenic stress (Timofeeva and Richard, 1997). Studies conducted in humans have also demonstrated that fasting and weight loss may increase circulating levels of cortisol (Beer et al., 1989, Dallman et al., 2004, Fichter et al., 1986 and Vance and Thorner, 1989) to potentially increase appetite in order to ‘defend’ an existing body weight (Doucet et al., 2000). This stimulating response appears to be more apparent in women in which subcutaneous fat could eventually protect against stress.
The goal of the present study was to investigate the effect of body weight and fat loss on the secretion of cortisol in response to the Trier Social Stress Test (TSST). The TSST is a standardized psychosocial stress test that has been extensively used. Because of the apparent importance of the nutritional status on the HPA axis activity, the TSST was performed in fed and fasted states. Based on previous data (Therrien et al., 2007), we predicted (i) that weight loss in men, in whom fat is predominantly deposited in the abdominal cavity, would reduce (compared to non-obese subjects) stress-induced cortisol secretion, and (ii) that weight loss in women, in whom fat is largely subcutaneous, would increase the stress response and that the increase would be enhanced by food restriction.
