Wednesday, August 18, 2010

Decreased Catecholamine Release in Obese Individuals: Another Weight Loss Obstacle

Jabbour et. al. (Jabbour. 2010) found that the exercise induced stress response in obese individuals is significantly reduced. The amount of catecholamines released in the course of 6 x 6sec maximal sprints with 2 min of passive rest between each repetition, was significantly lower in the 11 normal-weight adolescent boys compared to their 9 obese (body fat: 31.0 +/- 3.0%) and 11 overweight (body fat: 24.0 +/- 1.9%) age-mates:
Maximal epinephrine concentration was significantly (p<0.05) higher in lean vs. obese and was negatively correlated to body fat percentage (r=-0.60, p<0.05). Maximal norepinephrine values were higher in lean vs. overweight and obese and a negative relationship was found between maximal norepinephrine concentration and body fat percentage (r=-0.60, p<0.05). Maximal lactate concentration was higher in lean vs. overweight and obese (14.7 +/- 3.3, 10.4 +/- 2.7 and 10.2 +/- 2.5 mmol.l-1 in lean, overweight and obese respectively).
In view of the fact that both, epinephrine as well as its precursor, norepinephrine, are well known antagonists of alpha- and beta-receptors, which - apart from their vasoconstrictive properties - also elevate the blood sugar level by increasing hydrolysis of glycogen to glucose in the liver, and at the same time initiating the breakdown of lipids in adipocytes, this may well be another reason for obese people having an extra hard time to get rid of their extra pounds.