Rise of ketone bodies with psychosocial stress in normal weight men.

BACKGROUND: Ketone bodies are known as alternative cerebral energy substrates to glucose. During psychosocial stress, the brain of a normal weight subject demands for extra glucose from the body to satisfy its increased needs. In contrast, the brain of an obese subject organizes its need, supply and demand in a low-reactive manner. The present study aimed at investigating (i) whether psychosocial stress increases ketone body concentrations and (ii) whether ketone reactivity to a psychosocial challenge differs between normal weight and obese people. METHODS: Ten normal weight and ten obese men participated in two sessions (stress induced by the Trier Social Stress Test and a non-stress control session). Blood samples were frequently taken to assess serum ß-hydroxybutyrate concentrations and stress hormone profiles. RESULTS: Our main finding was that social stress markedly increased concentrations of serum ß-hydroxybutyrate by 454% in normal weight men. The increase in ketone bodies during stress in normal weight subjects was associated with an increase in ACTH, norepinephrine and epinephrine concentrations. Interestingly, we could not detect any increase in serum ß-hydroxybutyrate concentrations during stress in obese men. CONCLUSION: Normal weight men showed high ketone reactivity to a psychosocial challenge.

The brain's supply and demand in obesity.

During psychosocial stress, the brain demands extra energy from the body to satisfy its increased needs. For that purpose it uses a mechanism referred to as "cerebral insulin suppression" (CIS). Specifically, activation of the stress system suppresses insulin secretion from pancreatic beta-cells, and in this way energy-particularly glucose-is allocated to the brain rather than the periphery. It is unknown, however, how the brain of obese humans organizes its supply and demand during psychosocial stress. To answer this question, we examined 20 obese and 20 normal weight men in two sessions (Trier Social Stress Test and non-stress control condition followed by either a rich buffet or a meager salad). Blood samples were continuously taken and subjects rated their vigilance and mood by standard questionnaires. First, we found a low reactive stress system in obesity. While obese subjects showed a marked hormonal response to the psychosocial challenge, the cortisol response to the subsequent meal was absent. Whereas the brains of normal weight subjects demanded for extra energy from the body by using CIS, CIS was not detectable in obese subjects. Our findings suggest that the absence of CIS in obese subjects is due to the absence of their meal-related cortisol peak. Second, normal weight men were high reactive during psychosocial stress in changing their vigilance, thereby increasing their cerebral energy need, whereas obese men were low reactive in this respect. Third, normal weight subjects preferred carbohydrates after stress to supply their brain, while obese men preferred fat and protein instead. We conclude that the brain of obese people organizes its need, supply, and demand in a low reactive manner.