The triad of type 2 diabetes, obesity and cardiovascular disease : investigating optimal dietetic treatment strategies.

Obesity and type 2 diabetes (T2DM) are increasing in prevalence at an alarming rate. T2DM is a multifactorial disease that requires careful medical management of all its elements, often involving vast polypharmacy. Treatment options are under constant review to ensure that the morbidity and mortality associated with this chronic disease are reduced. Since the discovery that tighter control over glycaemia reduced the risk of developing microvascular complications, the use of insulin therapy in T2DM has expanded. However, insulin therapy has been associated with significant gain in body weight which potentially exacerbates the risk of cardiovascular disease. Dietetic clinics are often full of people with T2DM and obesity who tend to be resistant to current treatment strategies. This thesis contains a series of investigations that collectively contribute to the evidence base as to best practice in the dietetic management of T2DM. The first study uses a novel sensor that monitors interstitial glucose continuously over a 24 hour period. This study demonstrated that insulin treatment for people with T2DM did not improve glycaemic control compared to patients with T2DM treated with oral hypoglycaemic agents. Patients treated with insulin had wider daily variations of glucose, experiencing on average more than one hypoglycaemic event per day and spending over 9 hours hyperglycaemic. This study questioned whether insulin therapy actually achieves improved glycaemic control. Chapter 2 describes a randomised control trial which was designed to compare clinical outcomes in patients with T2DM who were newly starting insulin therapy. Subjects were randomised to follow either standard care or an intensive dietetic lifestyle intervention. Significant weight gain was associated with the introduction of insulin in the control group (5.6% body weight gain in 6 months), but weight gain was prevented in the intervention group (p<O.OO 1). The control group required more medications to counteract cardiovascular risk factors and reported poorer quality of life than those in the intervention group. In chapter 3, changes in postprandial metabolism were investigated in the first 6 months of insulin therapy. The sample size for this study was very small but in 3 out of 4 subjects there were trends towards improved postprandial glucose and lipid metabolism, in spite of weight gain. During the first six months of insulin treatment all patients became more insulin resistant. In the final study, with a case controlled retrospective design, a new dietetic led clinic with the ability to prescribe Sibutramine was compared to the outcomes achieved using diet and lifestyle advice only in overweight women with and without T2DM. This showed that people with T2DM have more difficulty in losing weight than people without T2DM when following Lifestyle intervention. In patients who were unable to lose weight following Lifestyle intervention alone, the addition of Sibutramine to Lifestyle advice enabled similar or greater amounts of weight 1m"> as pair matched patients who successfully lost weight in the Lifestyle clinic. These studies demonstrate that effective dietetic management for patients with T2DM result in positive outcomes, such as weight loss. However, changes to standard care would be required towards more intensive and longer term dietetic interventions as well as the use of pharmacotherapy. The treatment of obesity in T2DM needs to be more aggressive to enable people to manage their weight, and different weight loss strategies should be attempted until success prevails. Dietitians provide an excellent foundation on which new skills for obesity management can be built, which then urgently need to be implemented nationwide to help turn the tide on the obesity epidemic.