Management of type 2 diabetes: A handbook for general practice

Weight management interventions for type 2 diabetes

Management of type 2 diabetes: A handbook for general practice
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Weight management interventions for type 2 diabetes

Recommendation 

Grade 

References 

 Recommended as of:

In people with overweight or obesity with diabetes, a nutritionally balanced, calorie-reduced diet should be followed to achieve and maintain a lower, healthier body weight. 

A, Level 1A 

1-3 

14/11/2024

An intensive healthy behaviour intervention program, combining dietary modification and increased physical activity, may be used to achieve weight loss, improve glycaemic control* and reduce cardiovascular disease (CVD) risk. 

*glycaemic management

A, Level 1A 

2-4 

14/11/2024

Obesity pharmacotherapy should be considered for people with diabetes and overweight or obesity along with lifestyle changes. Potential benefits and risks must be considered. 

A 

5 

14/11/2024

People who achieve weight loss goals should be offered long-term (≥1 year) weight maintenance support which should, at minimum, involve monthly contact, ongoing monitoring and self-monitoring of weight and regular physical activity (200–300 min/week). 

A 

5,6 

14/11/2024

Consider metabolic surgery as a weight and glycaemic management approach in people with diabetes with  body mass index (BMI) ≥30.0 kg/m2 who are otherwise good surgical candidates. 

A 

5,7 

14/11/2024

Metabolic surgery should also be considered for people with type 2 diabetes and BMI 30.0–34.9 kg/m2 if hyperglycaemia is inadequately managed despite optimal treatment with either oral or injectable medications. 

Consensus 

5,7

14/11/2024

For people with type 2 diabetes who are overweight or obese, even modest weight loss (5–10%) may provide clinical benefits, including improved glycaemic management, blood pressure and lipid profiles, especially early in the disease process.8–10 Lifestyle-induced sustained weight loss contributes to the prevention, or delays the progression, of diabetes.11–13

However, the relationship between weight loss and clinical benefits is complex. The multicentre 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.14 This was despite greater reductions in glycated haemoglobin (HbA1c) and greater initial improvement in fitness and all CVD risk factors, except for low-density lipoprotein cholesterol levels. Increasing physical activity, regardless of weight loss, may reduce CVD risk factors,15 and reduce HbA1c by approximately 0.6% in adults with type 2 diabetes.16

The causes of overweight and obesity are likewise complex. Cultural and social issues have a strong influence on health behaviours such as diet and physical activity. A person-centred approach should be taken to support people to make choices that are consistent with their culture and social environment. 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. Older people with diabetes and those undergoing metabolic surgery may also be at risk of malnutrition.17

When managing people, be mindful that some medications are associated with weight gain, including insulin, sulfonylureas, thiazolidinediones, second-generation antipsychotics (especially olanzapine and clozapine), beta-blockers (especially propranolol), tricyclic antidepressants, lithium, pizotifen, sodium valproate and glucocorticosteroids.18

It is important to encourage a degree of a healthy lifestyle approach to managing diabetes. Where appropriate, develop a shared decision making plan on whether support may be needed for weight loss in anyone with type 2 diabetes who is overweight/obese. Exceptions, however, may arise if there are other associated risks (eg in the frail and elderly, or those with eating disorders). Because a healthy body weight is sometimes not achievable, setting this as an absolute goal might discourage people from attempting any dietary change. Avoidance of weight stigmatisation and a sole focus on weight loss may impact negatively on people living with diabetes. 

An accredited practising dietitian (APD) can provide practical and evidence-based approaches to supporting people considering, commencing and sustaining their weight goals. Additional health professional support may be appropriate, such as psychology, exercise science professionals and specialist metabolic/obesity services. The Australian Obesity Management Algorithm is a practical clinical tool to guide the implementation of existing guidelines for the treatment of obesity in the primary care setting in Australia.19

Weight assessment 

Weight can be assessed using BMI. However, this can be a difficult parameter to standardise between different population groups and may not adequately assess visceral weight gain, and thus additional measures, such as waist circumference, are helpful. Measuring waist circumference in people with a BMI >35 kg/m2 may not add any further to predictive disease risk classification.20 However, it can provide a non-weight health focus for the patient, should this be preferable to them. 

There are variable accepted ranges for BMI among different populations within the diabetes community. For those of European descent, a healthy BMI is 18.5–24.9 kg/m2, overweight is 25–29.9 kg/m2 and obese is ≥30 kg/m2.2,3 Different classification criteria may apply to other population groups. Some groups may have equivalent levels of risk of health problems at a lower BMI (eg these BMI thresholds should be reduced by 2.5 kg/m2 for people of Asian ethnicity21) or higher BMI (eg some Torres Strait Islander and Māori peoples).22 

It is advisable to also assess waist circumference (in centimetres) because this is a good indicator of total body fat and a useful predictor of visceral fat. Waist measurements of ≥94 cm in men and ≥80 cm in women convey increased risk of obesity-related complications; measures of ≥102 cm in men and ≥88 cm in women convey greatly increased risk.23 As with BMI, these values may differ for other population groups.3 

Lifestyle interventions for weight management 

In overweight or obese people with diabetes, advice from qualified health professional, such as an APD, on a sustainable, culturally appropriate, 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).2,24 

Advice to people with diabetes about medication use/deprescribing should accompany any dietary energy restriction and/or carbohydrate restriction and with progressing weight loss. Advising people using sodium–glucose cotransporter 2 inhibitors (SGLT2i) about the risks and management of euglycaemic ketoacidosis with fasting and/or higher-protein/lowered-carbohydrate approaches may be needed. Consider the impact of total protein intake in people with renal disease. Hypoglycaemia is important to manage clinically with dietary interventions, especially in people using medications that cause hypoglycaemia. Some diabetes medication may have non-glycaemic benefits, and it may be necessary to continue these (refer to ‘Medical management of glycaemia’). Timely monitoring and clinical advice should be actioned for any changes in glycaemic variability and cardiovascular and kidney disease risk factors (eg blood pressure and lipids); in addition, consider appropriate clinical evaluation and support of psychological health. 

Very low energy diets (VLEDs) can be considered as an initial weight loss strategy when supervised lifestyle interventions have been unsuccessful in reducing weight or when rapid weight loss is required (eg prior to bariatric or general surgery that is conditional on weight loss).19 These diets may be considered in adults with diabetes with BMI >27 kg/m2, taking into account each individual situation.19,25 The Diabetes Remission Clinical Trial (DiRECT), a primary care-based weight loss study, showed that VLED with associated weight loss led to 46% of participants reducing or ceasing diabetes medications after 12 months of intervention.26 (Refer to ‘Remission of type 2 diabetes’.) 

VLEDs require regular appointments with appropriate health professionals, such as an APD, to support an individual’s progress. Caution should be exercised if hypoglycaemia is a risk (people taking sulfonylureas and insulin). The use of SGLT2i in people on VLEDs or any high-protein/low-carbohydrate diet should be carefully considered, and the person educated on risks (due to a raised risk of ketoacidosis, which might be euglycaemic). 

The definition of ‘lower-carbohydrate’ diets varies, making for complexity in the translation of clinical trial results into pragmatic clinical practice. It is important to reassess and individualise meal plan advice regularly for people willing to consider this approach (consult an APD to support people with diabetes who wish to manage these dietary changes) to ensure adequate fibre intake, avoid micronutrient deficiencies and ensure saturated fat intake is optimal.2 General practice services, particularly in the UK, have been able to implement non-randomised multidisciplinary weight management approaches including low-carbohydrate diets that have supported people with diabetes achieve healthy outcomes, including lowered HbA1C and weight.27–29 

A recent (2022) Cochrane analysis30 of randomised trials of low-carbohydrate versus balanced-carbohydrate diets found there is probably little to no difference in weight reduction and changes in cardiovascular risk factors up to two years of follow‐up in overweight and obese participants without and with type 2 diabetes. Another systematic review with a stricter definition of ‘low-carbohydrate’ diets did show successful weight loss using both low-energy and lowered-carbohydrate approaches,31 and that evidence for longer-term efficacy beyond two years was lacking. Finally, an umbrella review of published systematic reviews and meta-analyses1 comparing the quality of evidence published for weight loss and type 2 diabetes showed that the greatest weight loss was reported with VLEDs, and that based on high-quality data, low-carbohydrate diets were no better for weight loss than higher-carbohydrate/low-fat diets. This divergence of evidence highlights that more longer-term studies (including randomised trials with dietary comparisons) and standardisation of definitions on lowered-carbohydrate approaches, with consistent measurable clinical endpoints, are still needed to consolidate the evidence.32 

The Australian Diabetes Society has a position statement outlining practical approaches to managing diabetes with therapeutic carbohydrate reduction.33 

Be clinically aware of higher-protein diets in people with, or those at risk of, real impairment.34 

Pharmacotherapy 

Pharmacotherapy for chronic weight management should be supported by healthy individualised lifestyle management. Pharmacotherapy for chronic weight management uses medications licensed by the Therapeutic Goods Administration (TGA) for weight management, including for people with diabetes, but none are currently reimbursed by the Pharmaceutical Benefits Scheme. These agents can be used as adjuncts to dietary changes and physical activity improvement and include phentermine (a sympathomimetic amine), orlistat (an inhibitor of intestinal lipase), liraglutide and semaglutide (glucagon-like peptide-1 receptor agonists [GLP-1RAs]) and combined naltrexone and bupropion. The addition of semaglutide (maximum 2.4 mg) to the TGA-approved list of GLP-1RAs that can be used in type 2 diabetes opens further opportunities for people to achieve meaningful weight loss before considering bariatric surgery. 

These drugs may be considered in adults with diabetes with a BMI ≥27 kg/m2, taking into account each individual situation.19 

Each drug has the potential for significant clinical side effects and contraindications associated with its use. The drugs require careful clinical risk–benefit assessment when applied in practice. Refer to the TGA website for more information. 

Surgical interventions 

Surgery for weight loss, also called metabolic or bariatric surgery, may induce weight loss in people who have failed to lose weight by other means. The following procedures are used in Australia.19,21,25,35 

  • Sleeve gastrectomy involves removing the greater portion of the fundus and body of the stomach, reducing its volume from up to 2.5 L to approximately 200 mL. This procedure provides fixed restriction and does not require adjustment like laparoscopic adjustable gastric banding (LAGB). 
  • Single/one anastomosis gastric bypass surgery involves a procedure in which a gastric pouch is formed from a division of the stomach and a small bowel bypass is connected to this pouch. 
  • Roux-en-Y gastric bypass is a combination procedure in which a small stomach pouch is created to restrict food intake, and the lower stomach, duodenum and first portion of the jejunum are bypassed to produce modest malabsorption of nutrients and thereby reduce kilojoule intake. 
  • Biliopancreatic diversion is also a combination procedure that involves removing the lower part of the stomach and bypassing the duodenum and jejunum to produce significant malabsorption. This procedure tends to be performed in subspeciality centres. 

Used in the past, LAGB is less used now in Australia and North America due to less sustained weight loss, fewer metabolic benefits and high surgical complication rates. This procedure involves placing a band around the stomach near its upper end to create a small pouch.3

Sleeve gastrectomy, Roux-en-Y gastric bypass and biliopancreatic diversion lead to sustained weight loss and normalisation of type 2 diabetes metabolic markers, although techniques vary in efficacy.3

The improvement in diabetes metabolic markers for Roux-en Y gastric bypass surgery at the two-year follow-up was 52.7% in one meta-analysis, compared with 0.7% for medical management.36 For individuals who achieve improvement in diabetes metabolic markers with Roux-en-Y gastric bypass, the median period of sustained improvement is 8.3 years.21 

In non-randomised studies, metabolic surgery in people with type 2 diabetes is associated with reductions in microvascular and macrovascular complications, as well as reduced cardiovascular mortality and non-fatal cardiac and renal events, versus non-surgical type 2 cohorts;37,38 however, the risk of suicide was higher in the surgical intervention groups. Moreover, studies have shown that metabolic surgery can prevent or delay the onset of type 2 diabetes in people with obesity,39 as well as the development of microvascular complications.40 

Taking into account each individual situation, metabolic surgery may be considered for people with a BMI >30–35 kg/m2 who have suboptimal blood glucose levels, are at increased CVD risk and are not achieving recommended targets with medical therapy.21 

General practitioners should assess the appropriateness of metabolic surgery for each individual and provide information on the risks, benefits and appropriateness of the type of procedure. Metabolic surgery performed in a high-volume specialist centre with an experienced surgical team may offer lower risks, and general practitioners should liaise with a specialised surgical team if there are concerns.19,25 

Metabolic 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.19

Adverse events of metabolic surgery, particularly in the long term, need more research;41 however, suggested follow-up care includes monitoring for nutritional deficiencies and acid reflux disorders.42 

Women of reproductive age who have had metabolic surgery need particular advice on contraceptive choices;43 those who plan to have a pregnancy need assessment, before and throughout pregnancy, regarding nutritional status, the need for higher multivitamin doses and close obstetric monitoring. Referral prior to pregnancy to appropriate speciality services is strongly advised, even if the diabetes appears well managed and the interval before recommending conception may extend to 18 months after surgery. 

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  2. Aas AM, Axelsen M, Churuangsuk C, et al. Evidence-based European recommendations for the dietary management of diabetes. Diabetologia 2023;66(6):965–85. doi: 10.1007/s00125-023-05894-8.
  3. Diabetes Canada Clinical Practice Guidelines Expert Committee. Diabetes Canada 2018 clinical practice guidelines for the prevention and management of diabetes in Canada. Can J Diabetes 2018;42(Suppl 1):S1–326.
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  40. Carlsson LMS, Sjöholm K, Karlsson C, et al. Long-term incidence of microvascular disease after bariatric surgery or usual care in patients with obesity, stratified by baseline glycaemic status: A post-hoc analysis of participants from the Swedish Obese Subjects study. Lancet Diabetes Endocrinol 2017;5(4):271–79. doi: 10.1016/S2213-8587(17)30061-X.
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  43. Shawe J, Ceulemans D, Akhter Z, et al. Pregnancy after bariatric surgery: Consensus recommendations for periconception, antenatal and postnatal care. Obes Rev 2019;20(11):1507–22. doi: 10.1111/obr.12927.
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