Managing obesity in people with type 2 diabetes

Key points

• Being overweight or obese is a key modifiable risk factor in the development of diabetes, with 90% of patients with diabetes being classified as overweight or obese.

• A multidisciplinary approach to management is recommended and assessment beyond BMI using obesity staging is valuable.

• Low-calorie diet programmes have been shown to support remission of diabetes and are currently being piloted throughout the UK.

• Medications used in the management of diabetes can have a positive, negative or neutral effect on weight. Potent weight loss maybe seen with newer agents.

• Bariatric surgery is a safe, effective therapy but is underutilised for people with type 2 diabetes mellitus and obesity.

Pathophysiology of obesity and T2DM

The mechanisms linking obesity and T2DM are complex and still being understood, but likely involve a combination of:

• adipose tissue release of excess circulating fatty acids, glycerol, hormones and pro-inflammatory cytokines, impairing cellular insulin signalling and increasing insulin resistance⁵

• chronically raised lipid levels leading to impaired islet beta-cell function and lower levels of insulin production.⁶

An approach to the patient with obesity and diabetes

An individual with T2DM and obesity may present to a range of specialties. Typically, recurrent patterns of dieting and weight regain are described (Box 1). As with obesity management in any context, this should be explored in a non-judgmental way and in the context of expected physiological changes which accompany dieting.⁸ It is also worth considering the many complex factors that contribute to obesity (Fig 1) alongside the stigmatisation and social isolation often experienced by patients.⁹

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Fig 1.

A simplified version of the full generic obesity system map clusters.⁹

Consideration of context will support the design of an effective and individualised care plan. Motivational interviewing and SMART goal setting are useful techniques. SMART goals are built around the following criteria: specific, measurable, achievable, relevant and time-bound. Assessment beyond body mass index (BMI) is also valuable; for example, King's Obesity Staging Criteria (Table 1) supports conversations around how obesity is affecting an individual.¹⁰ It may also form a useful framework to discuss intervention. A complete assessment of obesity requires a skilled multidisciplinary team.

Clinical assessment

Detailed history taking and evaluation is described elsewhere.¹¹ Aspects to consider include:

• age of onset of excess weight

• where onset was as a young child, whether other traits are present suggestive of genetic syndromes

• family history of obesity and its pattern, especially if severe obesity is dichotomously present with normal weight

• pattern of weight gain, noting periods of acceleration or weight loss and their relation to health or life events

• intake of alcohol or other highly calorific liquids

• success and failure of previous attempts at losing weight.¹¹

National Institute for Health and Care Excellence (NICE) guidelines (CG189) also provide further advice on the assessment of obesity.¹² During examination of a person with diabetes and obesity, aspects to consider include cardiovascular risk, secondary obesity (including genetic causes and endocrinopathies such as Cushing's syndrome) and sequelae (eg osteoarthritis and sleep apnoea). A thorough assessment, combined with a sensitive approach which considers context, provides the foundation to discuss intervention.

Lifestyle interventions

Individualised advice on diet and physical activity, combined with a personalised diabetes care plan, underpins all approaches. The Look AHEAD Trial compared a 4-year intensive programme (including lifestyle counsellor, dietary interventions, portion-controlled meal plans, physical activity and behavioural modification techniques) with a diabetes support/education (DSE) group and usual medical care.¹³ The intensive intervention group showed mean weight loss at 1 year of –8.6% versus –0.7% in the DSE group. This was sustained over 4 years with a mean weight loss of –6.15% and –0.88% in the intervention and DSE groups, respectively. In a separate study, an intensive diet intervention soon after diagnosis was shown to improve glycaemic control.¹⁴ Unfortunately, weight maintenance has been reported to be a challenge following lifestyle-induced weight loss.¹⁵

Low-calorie diets

T2DM has often been described as a chronic and progressive condition. The landmark Diabetes Remission Clinical Trial (DiRECT) demonstrated, however, that diabetes remission was possible through a low-calorie total diet replacement programme.¹⁶

The control group received best-practice diabetes care while the intervention group received a structured weight management programme and total diet replacement (825–853 kcal/day) for 12–20 weeks. This was followed by stepped food reintroduction over 2–8 weeks and support for weight maintenance. At 24 months, 36% of intervention participants achieved remission of diabetes (defined by HbA_1c <48 mmol/mol on no diabetic medications). The mean change in body weight between control and intervention group was –5.4 kg. Remission was closely related to weight loss, with 64% of those with at least 10 kg weight loss achieving diabetes remission. Sustained remission at 2 years for more a third of people with T2DM has been reported. Based on this evidence, the NHS Low Calorie Diet Programme is currently being piloted throughout the UK and may be effectively delivered in a primary care setting for people with obesity.¹⁷

In clinical practice, screening, engagement and specialist support are important elements for success of a total diet replacement programme. Close review of glycaemic control and diabetes ‘deprescribing’ are required. Behavioural support and self-monitoring are valuable components. Often people report appreciating the opportunity to ‘reset’ their relationship with food and eating; one patient commented ‘I’m currently on a total diet replacement (TDR) which means I don’t have to think about food choices’.

Recent evidence suggests that the prevention of weight regain following TDR may require the addition of components such as intensive exercise.¹⁸

Medical therapy

Prescribing options for T2DM and obesity have widened substantially in recent years. Large-scale trials demonstrate significant weight loss as well as cardiovascular benefits with agents such as glucagon-like peptide-1 agonists and sodium-glucose cotransporter-2 inhibitors. American Diabetes Association / European Association for the Study of Diabetes guidance reflects this and advocates treating T2DM with consideration for comorbidities such as obesity.¹⁹

When prescribing for a person with T2DM and obesity, it is useful to articulate that the agent is only a tool within a multicomponent treatment strategy. Full counselling on expected benefits, side effects and cessation criteria should be provided. This is particularly pertinent for women of childbearing age.

Challenges in prescribing include weight gain associated with certain agents and also with glycaemic improvement. Medications licensed for use in T2DM, mechanisms and overall weight effect are summarised in Table 2.¹⁹

Orlistat is licensed in the management of obesity and NICE recommends its prescription as part of an overall plan for managing obesity in those with BMI >30 kg/m² or >28 kg/m² with other associated risk factors. Side effects are often poorly tolerated, however.

Surgical therapy

Bariatric surgery is an effective and durable treatment for severe obesity, linked to improvements in obesity-related comorbid conditions as well as all-cause mortality. A systematic review and metanalysis of 621 studies with 135,246 patients undergoing a range of bariatric procedures reported an overall weight loss of 38.5 kg or 55.9% excess body weight loss.²⁰ 78.1% of diabetic patients reached remission and a further 8.5% had an improvement in their diabetic control. A low prevalence of relapse has been reported in those who achieve remission.²¹

Given the factors associated with diabetes remission, NICE recommend expedited bariatric surgery for people with BMI of 35 kg/m² or over who have recent onset T2DM (<10 years). Those with BMI 30–34.9 kg/m² and recent onset T2DM should also be considered for assessment. Lower BMI cut-offs (reduced by 2.5 kg/m²) are recommended for people of Asian origin.

Unfortunately, less than 1% of people who are eligible are referred for and receive this effective and safe intervention.²²

While surgery is typically safe in carefully selected and prepared individuals, complications including dumping syndrome and vitamin deficiencies are recognised.