Behavioral and physiological responses to stress are affected by high-fat feeding in male rats

Interactions between monoaminergic neurochemistry and macronutrient intake have been frequently shown. Because monoaminergic systems in the brain are also closely involved in behavioral and physiological stress responses it c an be hypothesized that differences in the macronutrient composition of die ts are reflected in these responses. The present studies, therefore, were d esigned to assess the consequences of a change in dietary macronutrient com position on a variety of physiological and behavioral responses (both acute and long-term) to a number of stressors. The effect of chronic high-fat (H F: 61% kcal from fat) feeding on the stress responses was compared with con trols receiving regular high-carbohydrate (HC; 63% kcal from carbohydrates) laboratory chow. Rats were kept on this diet for at least 2 months before they were exposed to either psychological (social defeat) or physiological (lipopolysaccharide, LPS, administration) stress. At baseline, chronic HF f eeding caused a slight, but significantly reduction in body temperature rel ative to that observed in HC-fed rats. Following social defeat or LPS injec tion, HF feeding caused a faster recovery of the body temperature increase relative to animals on the Hd diet. Stress-induced suppression of home cage locomotor activity and body weight gain were also reduced by HF feeding. T he serotonergic 5HT(1a) receptor hyposensitivity that was observed in HC-fe d rats 2 weeks after stress was absent in the HF regimen. Although the pres ent results cannot be readily interpreted as showing purely beneficial effe cts of high-fat diets on stress responsivity, the findings in the present s tudy do encourage further investigation of possible ameliorating effects of high-fat diets on aspects of the behavioral and physiological response str ess. (C) 2001 Elsevier Science Inc. All rights reserved.