Assessment of Obesity

Obesity particularly abdominal obesity increases the risk of cardiovascular morbidity and mortality. Hence it is very important to identify such diabetics and treat them at early stage.

Aetiological Link Between Obesity And Type 2 Diabetes

There is abundant evidence to implicate obesity as a risk factor for development of Type 2 diabetes, although it is not clear whether a common antecedent could lead to both Type 2 diabetes and obesity. This link is specially powerful with truncal obesity. Patients with high waist hip ratio and BMI have 15% risk of development Type 2 diabetes over 13 years periods. Abdominal fat increases insulin resistance and leads to hyperinsulinemia. At the same time it is clear that every obese patients does not develop diabetes hence genetic susceptibility plays a major role.

Insulin Secretion In Obese Type 2 Diabetics

Obese diabetics are hyperinsulinemic. This could be either due to (a) increased insulin production by pancreas or (b) decreased degradation by liver. But this hyperinsulinemia is inappropriately low for that level of blood glucose. As with other Type 2 diabetics they have attenuated / absent first phase and reduced second phase of insulin response. They have increased level of basal insulin secretion. Twenty four hours secretary rates are also increased and they correlate positively with BMI. Temporal pattern of insulin secretion is not altered. The pulsetality pulsations every 10-14 minutes. Although amplitude of individual pulse seems to be higher, it is normal if taken as % rise from basal levels. Figure 1 shows pattern of insulin secretion in Type 2 diabetics.

The mechanism behind increased insulin secretion remains elusive. The proposed mechanisms are:

• Primary increase in beta cell mass and subsequently increase in secretion.
• Hyerinsulinemia due to peripheral insulin alterations in secretion may be due to imbalance between cholinergic sympathetic nervous system.

Decreased hepatic clearance of insulin is due to :

• Increased portal FFA causing decreased binding of insulin to hepatocytes.
• FFA oxidation causes internalization of insulin receptors and decrease turnover insulin at receptor level.

Insulin abnormalities seen in obese diabetics are seen much before they manifest figure 2. These abnormalities in insulin secretion can be taken as predictors of Type 2 diabetes. Abnormalities of insulin secretion in obese diabetics can be reversed to some extent by reducing the weight.

Role Of Adbominal Obesity And FFA In IR Of Obesity

Abdominal adipocytes are unique as they have:

• Increased intrinsic metabolic activity
• More receptors for glucocorticoids and androgens
• More number of catecholaminergic nerve endings
• Higher blood flow.