Management of Obesity

The concordance rate for Type 2 diabetes is high about 60%. However, the fact that it is not 100% shows that even genetically predisposed individuals are not condemned to develop diabetes - environmental factors are also important. This is encouraging, because it means that a large proportion of the risk is potentially modifiable. It also means that, people with a genetic predisposition, should be warned to control obesity and other risk factors.

No single gene for Type 2 diabetes has been identified, except in the case of maturity-onset diabetes of the young (MODY). Other candidate genes have been proposed, including those coding for glucokinase, insulin, and the insulin receptor. However, no clear association between these genes and the presence of Type 2 diabetes has so far been demonstrated.

The more common forms of Type 2 diabetes are likely to be polygenic, resulting from an interaction between different frequent gene variants, each of which have individual, small effects on glucose tolerance. Interaction between these different genes, and between the genes and the environment leads to Type 2 diabetes. Type 2 diabetes and cardiovascular disease share a common genetic background. It has been proposed that a thrifty genotype of 'diabesity' gene may be responsible for the development of obesity and its adverse consequences. In evolutionary terms, such a genotype would have protected our ancestors against starvation by ensuring the efficient storage of any excess calories as fat. In modern times, with a more than adequate food supply, however, this genotype would lead to obesity, and from there to Type 2 diabetes and cardiovascular disease.

Early - Life Influence

Low birth weight and low weight gain during the first year of life are associated with the occurrence of Type 2 diabetes, hypertension and hyperlipidaemia (Syndrome X), decades later in adult life. Low birth weight has also been shown to predict the future development of abdominal obesity.

It has been suggested that inadequate nutrition during foetal development and early life might lead to inadequate development of pancreatic islet cells, predisposing to islet cell failure, and diabetes, it has also been proposed that if inadequate nutrition in early life limits adipocytes development, storage of excess calories in adult life is more likely to occur in the visceral adipocytes, which hypertrophy more readily than those in other parts of the body.

Management

Can Weight Loss Prevent Or Treat Type 2 Diabetes ?

Even quite modest levels of weight loss can have an impact on the obese person’s risk of developing Type 2 diabetes. And although weight loss cannot be expected to reverse pancreatic dysfunction in established diabetes, it can achieve quite striking improvements in diabetic control. This may reduce or even eliminate the need for hypoglycaemic agents. There is also an evidence that weight loss can reduce mortality in diabetic patients.

Prevention Of Diabetes

There is a convincing evidence that weight loss can prevent or delay progression to diabetes in obese patients. In the Nurses’ Health Study women who lost more than 5 kg over a 10 year period reduced their risk for diabetes by 50% or more.

In the Malmo study, individuals with IGT took part in programme of weight loss combined with increased physical activity. The treatment group lost a mean of 6 kg over the first year, and maintained a weight loss of 2.0 – 3.3 kg after 5 years, whereas the control group gained 0.2-2.0 kg. At five years, 29% of the control groups had developed diabetes, compared with only 11% of the treatment group. Again, this suggests that a relatively modest weight loss substantially reduces risk.

Blood Glucose Control

A loss of as little as 5 kg has been shown to be beneficial in obese diabetics.

In the UK Prospective Diabetes study, the more weight patients lost, greater the improvement in blood glucose. However, weight loss does not have to be very great in order to achieve clinically relevant benefits. In one long-term study, patients who lost more than 6.9 kg or had more than a 5% reduction in body weight, had significant improvements in glycosylated haemoglobin values at one year.

Some patients with Type 2 diabetes show a much better plasma glucose response to weight loss than others. Those who are going to improve usually start to do so early after a weight loss of only 2-4 kg. There also appears to be effect of calorie restriction independent of weight loss.

Insulin Sensitivity

Both peripheral sensitivity and the ability of insulin to suppress hepatic glucose output are improved as weight is lost. The insulin response to a glucose load tends towards normalization after weight reduction, whether it is initially elevated (as in patients with IGT but to diabetes) or blunted (as in patients) with franks diabetes. Plasma FFA and lipid oxidation are reduced after weight loss, leading to improved glucose storage, and glucose uptake. All aspects of glucose of uptake into muscle and adipose tissue are improved with weight loss. Binding of insulin to its receptor is improved, as is glucose transport into muscle, Tyrosine kinase activity in adipocytes is also improved after weight loss, thereby activating insulin effects within the cell.

Dyslipidaemias

Weight loss has been found to ameliorate all the dyslipidaemias that occur in obese Type 2 diabetics. For example, a one – year study found a significant reduction in triglycerides in patients who lost 2.4 kg or more, and a significant increase in HDL cholesterol in those who lost 6.9 kg or more. The greater the amount of weight lost, the greater the improvement in the lipid profile. The American Diabetes Association recommends weight loss as the First - line treatment in the management of lipid disorders and prevention of related cardiovascular disease in diabetes.

Effects On Complications

There have been no specific studies on the effects of weight loss on the complications of Type 2 diabetes, such as retinopathy, neuropathy, or cardiovascular disease. However, there is ample evidence that weight loss reduce blood pressure in obese patients with and without diabetes. This may be expected to have a beneficial effect on the vascular complications of diabetes.

There is also compelling evidence that weight loss reduces cardiovascular morbidity and mortality, and again this should apply to diabetic as well as nondiabetic individuals – perhaps even more so.

Effects On Mortality

There is evidence from a retrospective study that patients with Type 2 diabetes who lose weight live longer. Survival was prolonged by 3-4 months for each kg of weight lost.

Benefits Of A Low – Fat Diet

A diet with a low fat : carbohydrate ratio is therefore likely to have the greatest effect on weight loss, and the greatest metabolic benefit.

Additional Benefits Of Exercise

Regular exercise can improve glucose tolerance decrease plasma insulin and improve the lipid profile in obese individuals. Some benefits of exercise may be related to a change in body fat mass (especially in visceral fat) although there also seems to be an independent effect. It seems prudent to recommend increased physical activity to all obese & obese diabetic patients, in combination with dietary manipulation as part of an overall lifestyle management programme.