Effect of dietary restriction on peripheral monoamines and anxiety symptoms in obese subjects with metabolic syndrome

Reduced circulating monoamines may have a role in the development of the metabolic syndrome (MetS), which is becoming a major health problem worldwide. Moreover, an association between anxiety disorder and MetS has been reported; however, it is not clear whether weight loss can diminish anxiety. This investigation is aimed to examine the effects of a weight loss intervention on peripheral monoamines levels and anxiety symptoms in subjects with metabolic syndrome (MetS). The study population encompassed subjects with MetS (age: 50 ± 10 y.o. and BMI: 35.8 ± 4.3 kg/m2) selected from the RESMENA study after they had completed the 6-month weight loss intervention (−30% energy). Anthropometric measurements, dietary records, anxiety symptoms, and blood monoamines levels were analysed before and after the intervention. Dopamine (DA) (+18.2%; 95% confidence interval (CI): −51.2 to −0.5) and serotonin (5-HT) (+16.1%; 95% CI: −26.3 to −2.2) blood levels were significantly increased after the intervention. Higher DA blood concentrations at the end of the study were inversely related with the carbohydrate intake during the study (B = −3.3; 95% CI: −8.4 to −0.4) and basal DA levels predicted a greater decrease in body weight and anthropometric parameters. Subjects with higher 5-HT concentrations after the weight loss intervention also showed a lower energy intake during the intervention (B = −0.04; 95% CI: −0.07 to −0.01). Additionally, anxiety symptoms decreased after the weight loss treatment (−28.3%; 95% CI: 6.2-20.4), which was parallel to a greater decrease in body weight and anthropometric markers, being related to lower 5-HT basal levels. Dietary restriction in patients with MetS may help in reducing anxiety symptoms, and also in increasing 5-HT and DA blood levels. These results provide further insights regarding emotional and neurological factors behind weight loss.