Psychobiology of Appetite and Food Reward in Type 1 and Type 2 Diabetes: Is there a Role for Exercise?

Hyperglycemia is the defining feature of type 1 diabetes (T1D) and type 2 diabetes (T2D) and results from deficient insulin production, impaired insulin-stimulated glucose uptake or both. It is now well established that hyperglycemia results in profound metabolic complications, but the effect of diabetes and its associated metabolic effects on homeostatic and hedonic appetite control has received less attention. Inappropriate food choices and excess food intake might promote weight gain, further exacerbating the metabolic consequences of T1D and T2D. The need to control blood glucose through diet, physical activity and/or medication as a consequence of impaired insulin secretion and/or sensitivity adds a further level of physiological and behavioural complexity to the processes underlying food choice and appetite control. Alterations in appetite-related processes have been noted in people with T2D, but the effect of T1D on appetite is largely unexplored. Peripheral neuroendocrine signalling appears disrupted in people with T2D, and brain regions involved in the central modulation of appetite might display central insulin resistance. However, it is difficult to isolate the consequences of T2D from those of obesity. Health-care policy advocates the use of physical activity as a means of preventing and treating T2D via the promotion of weight loss and its independent influence on insulin sensitivity. Exercise-induced perturbations to energy balance can elicit biological and behavioural compensation that attenuates weight loss, and diabetes pathophysiology might alter the strength of such compensation. However, the effect of exercise on appetite in people living with diabetes has yet to be fully explored.