Integrating components of energy intake in impaired glucose tolerant and type 2 diabetic populations

Objective - During feeding there is an integrated ‘whole body’ response which endeavours to maintain energy homeostasis. The integrated response consists of sensory, postingestive, postabsorptive and cognitive feedback which exerts control over ingestive behaviour. It is accepted that when an imbalance in this integrated response occurs and may promote an increased fat mass and ultimately can lead to obesity which is known to play an important role in the development of IGT and type 2 diabetes. This study investigated the integrated responses of a test meal to determine any differences between IGT, type 2 diabetics and controls in their integrated response mechanisms. This knowledge may be important in both predicting the onset of these diseases and in the treatment of them. Research Design and Methods - IGT and type 2 diabetics with a BMI greater than 30 and were recruited together with a group of healthy controls. The study assessed habitual energy intakes and energy expenditure in all groups. All participants’ height, weight, BMI and WHR were measured. A taste test assessed the sensory component of food intake. The metabolic response and parallel changes in appetite to the meal were recorded at baseline and at 15, 30, 60, 90 and 120 minutes. Results - Control participants had significantly lower weight (p<0.01), BMI (p<0.01), waist (p<0.01) and hip (p<0.01) measurements compared to IGT and the type 2 diabetic groups. Habitual diet diaries indicated a lower sugar intake in the type 2 diabetic group compared with IGT and control groups. Percentage protein intake was significantly lower in control participants (14.4%, p<0.05) compared to IGT (17.2%) and type 2 diabetics (18.5%). Activity diaries highlighted an indication of increased strenuous/physical activity in the control participants compared to IGT participants however, this was not statistically significant. The control group showed greater sensitivity to PROP followed by type 2 diabetics and then IGT participants (p<0.05). Throughout the study the control participants rated themselves the most hungry compared to IGT (p<0.05) and type 2 diabetics (p<0.01) respectively and controls were also the least satiated (p<0.05). There was no difference in fullness ratings. Control participants rated prospective consumption the highest compared to IGT and then type 2 diabetics (p<0.05) respectively. The differences in EE measured by calorimetry when normalised for body weight indicated that IGT (p<0.01) and type 2 diabetic participants (p<0.01) had significantly lower EE than control participants. CHO oxidation rates were significantly lower in IGT and type 2 diabetics (p<0.05). Investigating the blood parameters showed no differences in plasma ghrelin responses, that IGT participants had the highest overall plasma glucose (p<0.01) and insulin (p<0.05) responses. Conclusions - It is clear that there are subtle differences in the pathways of energy balance in IGT and type 2 diabetics compared to controls; including sensitivity to taste, subjective feelings of appetite, EE, oxidation rates and differing blood parameters. Taste appears to be an important contributor to the sensory control of food intake and is associated with an increased sugar intake. Furthermore, differences between IGT and type 2 diabetics demonstrate that the degree of management of the disease can influence the effectiveness of the metabolic pathways controlling food intake. It is not clear which component is the most influential in the control of food intake and it is likely that the synergistic effects are what potentiate the diseases and make them difficult to combat.