General practice management of type 2 diabetes

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Adults with impaired fasting glucose, impaired glucose tolerance or diabetes can be strongly advised that the health benefits of 5–10% weight loss include prevention, delayed progression or improved control of type 2 diabetes


NHMRC, 2013


For adults with body mass index (BMI) >40 kg/2), or BMI >35 kg/2) and comorbidities that may improve with weight loss, bariatric surgery may be considered, taking into account the individual situation


NHMRC, 2013


Use BMI to classify overweight or obesity in adults


NHMRC, 2013


For adults, use waist circumference, in addition to BMI, to refine assessment of risk of obesity-related comorbidities


NHMRC, 2013


*Refer to Summary, explanation and source of recommendations for an explanation of the level of evidence and grade of evidence

Clinical context

Excess weight in individuals usually results from a prolonged period of energy imbalance. However, the causes of overweight and obesity are complex. Older people with diabetes may also be at risk of malnutrition. Diet and physical activity are central to the energy balance equation, but are directly and indirectly influenced by a wide range of social, environmental, behavioural, genetic and physiological factors, the relationships between which are not yet fully understood. Increasing physical activity regardless of weight loss may reduce CVD risk factors, improve functional mobility in older people and reduce HbA1c by ~0.6% in adults with type 2 diabetes.78 Table 4.4 in Clinical practice guidelines for the management of overweight and obesity in adults, adolescents and children in Australia78  lists common medications associated with weight gain at 12 weeks of commencement of a weight management diet.79

 It is important to encourage some degree of healthy weight loss, except where there are other associated risks (eg frail and elderly, or those with psychologically related eating disorders). A healthy body weight is often not achievable and setting this as a goal discourages patients from attempting any dietary change. Many studies suggest that weight loss of 5–10% will improve glycaemic control.80, 81 .Section 2.2.3 in the above clinical practice guidelines discusses the importance of psychological issues influencing weight management.78

A recent multi-centre, randomised clinical trial (Action for Health in Diabetes [Look AHEAD]) provided evidence that intensive lifestyle intervention focusing on weight loss did not result in a significant reduction in cardiovascular events in overweight or obese adults with established type 2 diabetes.82 This was despite greater reductions in HbA1c and greater initial improvement in fitness and all CVD risk factors, except for low-density lipoprotein cholesterol levels.

In practice

Weight assessment

Assessing weight is typically done using BMI. Note that BMI is a difficult parameter to standardise between different population groups.

For those of European descent, a healthy BMI is 18.5–24.9 kg/2), overweight is 25–29.9 kg/2) and obese is ≥30 kg/2).78 Different classification criteria may apply to other population groups. Some groups may have equivalent levels of risk at a lower BMI (eg people of Asian origin) or higher BMI (eg Torres Strait Islander and Maori peoples).83

It is advisable to also assess waist circumference (in cm) as this is a good indicator of total body fat and useful predictor of visceral fat. Waist circumference of ≥94 cm in men and ≥80 cm in women conveys increased risk; ≥102 cm in males and ≥88 cm in females conveys high risk.84 As with BMI, these values may differ for other population groups.78 Measuring waist circumference in patients with a BMI >35 kg/2) may not add any further to predictive disease risk classification.85

Weight management

Modest weight loss (5–10%) may provide clinical benefits for those with type 2 diabetes, especially early in the disease process.75 Loss of body weight often results in improved glycaemic control, BP and lipid profiles. Sustained weight reduction of approximately 5 kg is associated with a reduction in HbA1c of approximately 0.5–1%.78 In adults with BMI <35 kg/2) with dysglycaemic states or hypertension, weight loss of at least 2–3 kg achieved with lifestyle interventions may result in a clinically meaningful reduction in BP (an average SBP of 4.5 mmHg and DBP of 3–3.5 mmHg).78

In overweight or obese people with diabetes, a nutritionally balanced, energy-reduced diet should be recommended if a lower, healthier body weight is to be achieved and maintained as part of a multicomponent lifestyle intervention (including healthy eating, physical activity and support for behavioural change).

Very low energy diets are a useful intensive medical therapy for supporting rapid weight loss when used under medical supervision.78 This involves regular appointments with appropriate health professionals aimed at supporting the progress of the individual. These diets may be considered in adults with a BMI >30 kg/2), or with BMI >27 kg/2) and obesity-related comorbidities, taking into account each individual situation.

Pharmacotherapy is licensed by the TGA for weight management, including for patients with diabetes, but is currently not PBS reimbursed. All agents are to be used as adjuncts to dietary changes and physical activity improvement. Agents available include phentermine (a sympathomimetic amine), orlistat (an inhibitor of intestinal lipase) and liraglutide (a glucagon-like peptide-1 receptor agonist [GLP-1 RA]). Each agent has the potential for significant clinical side effects and contraindications associated with its use, and require careful clinical risk–benefit assessment when applied in practice. Refer to the TGA website for more information.

Taking into account each individual situation, bariatric surgery may be considered for people with a BMI >30 kg/2) who have suboptimal blood glucose levels and are at increased CVD risk and who are not achieving recommended targets with medical therapy.78 GPs should assess the appropriateness of surgery for each individual patient and provide information on the risks, benefits and appropriateness of the type of procedure. Bariatric surgery performed in a high-volume specialist centre with an experienced surgical team may have the lowest risks and GPs should liaise with a specialised surgical team if there are concerns.78 Bariatric surgery, when indicated, should be included as part of an overall clinical pathway for adult weight management that is delivered by a multidisciplinary team (including surgeons, APDs, nurses, psychologists and physicians), and includes planning for surgery, and continuing follow-up.78

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