## 4 Discussion  
The main finding was the lack of clear associations between the KP and psychosomatic disorders, which was unexpected (Table 3). Most reviews and studies pinpoint the importance of the KP for mental health and psychological disorders [1; 3; 4; 15; 16; 17]. As seen in this study, the burden of psychosomatic comorbidity in subjects with turbid obesity is not insignificant. It was, therefore, expected to find associations between the psycho-somatic disorders and the KP. Some studies have shown associations between KP and fibromyalgia and chronic fatigue [11; 18]. In this study, neither fatigue nor muscle-skeletal pain (fibromyalgia-like symptoms) were associated with the KP. Daytime sleepiness is a frequent disorder in subjects with depression, and the sleepiness scores before surgery were nearly as high as in subjects with depression [31]. The slight negative association between KY/QA and sleepiness in this study, the same association as has been reported between KY/QA and depression, indicates that sleepiness and depression are related disorders [32]. The favourable effects of the KA/Kyn ratio reported in other studies might be reflected in the tendency to associate with improved self-esteem in this study [11]. One explanation for the lack of clear associations between the KP and psychosomatic disorders could be that the psychosomatic disorders were, nevertheless, not severe. Subjects with severe anxiety, depression, or other psychiatric disorders in need of treatment, were excluded from the study and offered other treatment. Another explanation is that the pronounced metabolic disorders in subjects with turbid obesity, which affects the KP, might have obscured the associations between KP and the psychosomatic disorders. The third explanation could be poor correlation between KP in serum and the cerebrospinal fluid. Tryp and Kyn easily pass the blood-brain barrier, and 60-80% of Kyn in the brain is of exogenous origin [1; 33]. In contrast, KA and QA hardly cross the blood-brain barrier, and the values in serum might be invalid markers of psychosomatic disorders [34]. Measures of the KP in cerebrospinal fluid could have given other results. In all, the study indicates that the peripheral KP is of minor importance for the psychosomatic comorbidity in subjects with obesity. All KP metabolites and their ratios were reduced after bariatric surgery. Other studies have reported these findings in subjects with obesity undergoing surgery with the same surgical methods [8; 10]. The downregulation from high to normal values has been judged as favourable and interpreted as reduced inflammation. The interpretation is confirmed by the reduction in CRP and positive associations between CRP and the KP metabolites, particularly with the Kyn/Tryp ratio, a known marker of inflammation [1; 2; 3]. The metabolic improvements are, however, not accompanied by a reduction in the adipose tissue inflammation [35]. High values of the KP metabolites, especially Kyn, KA, and XA, have been reported in subjects with DM type II and are potential tools for evaluating cardiovascular risk [2]. After surgery, the reduced KA/Kyn and KA/QA ratios could indicate reduced exercise and reduced neuroprotection, respectively, which did not fit the improved physical activity and mental health [1; 3; 13; 14]. The reduced QA/XA ratio after surgery was not compatible with the improved glucose tolerance measured as reduced HbA1c and s-glucose after surgery [2; 8]. The results reveal the uncertain relations between clinical disorders and the KP metabolites. There were several significant associations between the KP and variables assumed to interfere with the KP (Table 2). After adjusting for multiple testing, one of the statistically significant findings was the positive association between the Kyn/Trypt ratio and CRP, also seen in another study [8]. Inflammation is upregulated in subjects with obesity, and the Kyn/Trypt ratio is a well-known marker of inflammation [1; 2; 3; 5; 7; 10].