It has become clear that in certain contexts, such as in older people and in those with a variety of diseases, obesity is not as adverse as had been thought. This is referred to as the “Obesity Paradox”. Obesity before middle age certainly is harmful. The laboratory has been exploring whether there might be a neuroscience explanation of the obesity paradox. We have been investigating the sympathetic nerves of the heart in lean, and obese patients with hypertension. The cardiac sympathetic nerves have a definite potential to cause 'mischief' in the heart.
In a recent analysis we have found that obese patients with high blood pressure are free of a range of noxious changes in the cardiac sympathetic nerves which are present in patients with normal-weight hypertension. In lean hypertensive patients cardiac sympathetic outflow to the heart is activated, sympathetic nerve fibres fire in grouped salvos which causes extra stimulation, the reuptake of the neurotransmitter (noradrenaline) after its release is faulty such as to intensify the nerve signal, and surprisingly, adrenaline is released as a second transmitter from the sympathetic nerves of the heart. None of these potentially toxic features are present in obesity-hypertension. We think this might be an explanation of the obesity paradox.