Weight management in people with type 2 diabetes

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mary of the clinical guidelines (Expert Panel, 1998) which recommended .... Lihua Wu received a 2006 Mary Seacole Development Award. Arterburn D, Noel PH ...
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Weight management in people with type 2 diabetes Lihua Wu, Alison While

Lihua Wu is a Phd student and Alison While is Professor of Community Nursing at King’s College London, Florence Email: [email protected] Nightingale School of Nursing and Midwifery.

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iabetes mellitus is a heterogeneous disease of metabolism characterised by alterations in carbohydrate, fat and protein metabolism secondary to absent or reduced secretion and/or ineffective insulin action resulting in hyperglycaemia (Williams and Pickup, 2003). Type 2 diabetes mellitus is the commonest form of the disorder (Klodawski, 2004; NIH, 1999) and refers to individuals who have insulin resistance and insulin levels that frequently appear normal or elevated but are insufficient to compensate for insulin resistance. The prevalence of Type 2 diabetes has increased rapidly in the past two decades worldwide (WHO, 2005). The Wanless report (2004) noted that there are 1.1 million patients with Type 2 diabetes in England and with around another million thought to be undiagnosed. Type 2 diabetes is associated with a broad range of complications and early mortality which leads to a high cost both in human and economic terms. The global statistics indicate that the burden of Type 2 diabetes is not restricted to the developed nations, such as UK, where the demand for health care support is challenging the current health care service, but is also a worldwide phenomenon.

Understanding Type 2 diabetes The causative mechanism for the disease is complex and related to both natural and nurtured precedence. While there are some genetic elements and other factors that may predispose to Type 2 diabetes, the current diabetic epidemic has been accompanied by a similarly rapid increase in obesity. Within the current Type 2 diabetic population, 90% are obese or overweight (WHO, 2006). In exploring the pathophysiology of Type 2 diabetes, insulin resistance and beta-cell dysfunction are fundamental defects known to precede the onset of Type 2 diabetes (UKPDSG, 1995; Reaven, 1998). Insulin resistance presents when the biological effects of insulin are less than expected for both glucose disposal in skeletal muscle and suppression of endogenous glucose production primarily in the liver (Dinneen et al, 1992). Insulin resistance is strongly associated with obesity and physical inactivity with several mechanisms mediating this interaction. A number of circulating hormones, cytokines, and metabolic fuels, such as non-esterified (free) fatty acids (NEFA) originate in the adipocyte and modulate insulin action. An increased mass of stored triglyceride, especially in visceral or deep subcutaneous adipose depots, leads to large adipocytes that are themselves resistant to

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the ability of insulin to suppress lipolysis. This results in increased release and circulating levels of NEFA and glycerol, leading to a problem with both insulin resistance and insulin secretion in skeletal muscle and liver (Boden, 1997). Studies also report that obesity has a clear association with the insulin resistant related problems of glucose intolerence, hyperglycaemia, dyslipidemia, and hypertension, the so called ‘deadly quartet’ of the metabolic syndrome (Maggio and Pi-Sunyer, 1997; Wing, 2000). The estimated prevalence of the metabolic syndrome in the UK, which poses a major cardiovascular risk, has risen from 910,000 to 2 million in less than a decade (Duncan et al, 2004).Thus obesity is one of the primary factors underlying the alterations in metabolism that not only cause Type 2 diabetes but also lead to diabetes associated complications which impact upon overall quality of life.

The prevalence of obesity Obesity is not an isolated phenomena in the UK, but one of the greatest global public health challenges of the 21st century. WHO (2004) have reported that obesity has reached epidemic proportions globally, with more than 1 billion adults being overweight and at least 300 million of them clinically obese. It is contended that obesity is a major contributor to the global burden of chronic disease and disability accounting for 2-8% of health costs and 1013% of deaths in different parts of the European region with about 2.5 millions deaths being attributed to overweight/obesity worldwide (WHO, 2006). The prevalence of overweight and obesity is commonly assessed by using body mass index (BMI), defined

Abstract

This article sets out a comprehensive outline of the mechanism for the development of Type 2 diabetes and the importance of weight reduction in Type 2 diabetes management. Current weight reduction strategies are reviewed. Lifestyle modifications form the frontline strategy for targeted weight loss in diabetes care. However, there is a lack of knowledge regarding effective and safe interventions to promote weight management for those who have already developed Type 2 diabetes.

KEY WORDS

Type 2 diabetes w Obesity w Lifestyle modificationsw Weight management



TOPIC HEADER as the weight in kilograms divided by the square of the height in metres (kg/m2). A BMI over 25 kg/m2 is defined as overweight, and a BMI of over 30 kg/m2 is defined as obese (WHO, 2000). Within those having a BMI more than 30, there are three levels of obesity defined: obesity I: 30-34.9; obesity II: 35-39.9; Obesity III: 40 or more (WHO, 2000). However, obesity is not only about weight gain but is also concerned with the nature of weight gain. Thus issues relating to obesity should be taken into consideration when identifying the clinical risk of obesity, such as fat distribution, age, gender and ethnic group specific issues. The importance of fat distribution has been confirmed by epidemiological and metabolic studies which have shown that complications of obesity are more closely related to the distribution of the excess fat rather than to excess weight per se (Vague, 1947). The major risk factor responsible for diabetes, cardiovascular disease and mortality is the high proportion of abdominal fat rather than peripheral fat. The accumulation of central fat lies at the core of the metabolic dysfunction in diabetes. Thus central obesity, which refers to the amount of white or visceral fat stored by the body, is a major clinical and public health issue.

‘The major risk factor responsible for diabetes, cardiovascular disease and mortality is the high proportion of abdominal fat rather than peripheral fat’

Gender Gender is another factor to be considered concerning the risk of obesity. It is reported that the risk for diabetes mellitus for those with a BMI above 35 kg/m2 increases by 93-fold in women compared to 42-fold in men (Chan et al, 1994). Moreover, there are more confounding factors relating to the risk of coronary heart disease for women than men, such as the menopause which is associated with a selective deposition of visceral adipose tissue. Lean et al (1995) proposed two cut-off values for waist size which indicate the greater risk for the development of chronic metabolic diseases: 88cm for women and 102 cm for men. However, the International Diabetes Federation (2000) has pointed out that waist circumference should not only be gender specific but also ethnic group specific because there are major ethnic differences in the interrelations between waist circumference and the accumulation of visceral adipose tissue. Thus waist circumference cut-off references developed in white men should not be extrapolated to other ethnic groups; ethnic considerations are critical to interpreting the risk from weight and waist circumference. For example, in Asians it is estimated that there is increased risk above 90cm for males and above 80cm for females. In addition, with age there is a selective deposition of visceral adipose tissue (Lemieux et al, 1996a). For example, a waist circumference of 95cm for a middle-aged man means more visceral adipose tissue than in a young adult man with a similar waist circumference (Lemieux et al, 1996b). Therefore, interpretation of waist measure-



ments should also be related to the patient’s age. However, waist circumferences are rarely measured and interpreted in clinical practice despite of research evidence suggesting that it is a better predictor of cardiovascular risk than overall body weight as it correlates with a patient’s visceral fat (Despres et al, 2001). The benefits of weight loss in diabetes management Type 2 diabetes and obesity are threatening to overwhelm the capacity of health care service providers as they are associated with greater use and cost of services (Friedman & Fanning, 2004) and lead to reduced quality of life for individuals. The benefits of weight loss have been well studied (Jung, 1997; Lean & Anderson, 2001). Research evidence has consistently suggested that weight loss, even modest loss of 5%~10% of initial body weight produces significant clinical benefits and is easier to maintain than larger weight losses (Goldenstein, 1992; Jung, 1997; Williamson et al, 2000; Klein, 2001). Figures presented in Table 1 show the potential clinical benefits of 10kg weight loss on mortality, and the metabolic and cardiovascular systems. More specifically, Zimmet et al (2005) reported that weight loss could reverse the progression of Type 2 diabetes by reducing insulin resistance and the associated risk of cardiovascular disease. Indeed, it is argued that modest weight reductions (5%~10% of initial body weight) can halve the risk of developing diabetes and make many of the clinically beneficial effects achievable (reduction in the sum of risk factors: systolic blood pressure, serum triglyceride, total cholesterol, fasting blood glucose, and lowest quintile of high-density lipoprotein cholesterol) (Zimmet et al, 2005). This is because obesity has a strong association with insulin resistance, and this relationship applies to all ethnic groups and the full range of body weights especially where individuals exhibit central fat distribution are more prone to insulin resistance. Despite the complex relationship between obesity and Type 2 diabetes, it is clear that weight reduction is the central concept for Type 2 diabetes management. In light of this it is important to raise the awareness of weight management in diabetes clinical care and find effective strategies which facilitate weight loss in daily practice.

Strategies for weight loss The WHO (2006) has suggested that effective weight management for adults at risk of developing obesity involves a range of long-term strategies. These include prevention, weight maintenance, management of co-morbidities and weight loss. The key elements of the population-based approach includes creating supportive population-based environments through public policies that promote the availability and accessibility of a healthy diet, and provision of opportunities for physical activity; promotion of healthy behaviours to encourage, motivate and enable individuals to lose weight; development of a clinical response to the existing burden of obesity and associated conditions through clinical programmes and staff training to ensure

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TOPIC HEADER effective support for those affected to lose weight or avoid further weight gain. The first national guidance on the prevention and management of overweight and obesity is under development. In the draft on “what works” and best practice for the prevention and management of obesity, lifestyle interventions have been suggested as the first line of obesity management strategies with pharmacological interventions being recommended only after dietary and exercise advice have been initiated. Surgical interventions are only to be considered when all appropriate non-surgical measures have failed to achieve or maintain adequate clinically beneficial weight loss for at least 6 months (NICE, 2006). Evidence from reviews regarding the effectiveness of different interventions for treating obesity is available but has not been updated recently (Harvey et al, 2006). The Effective Health Care Bulletin (1997) and the report by the National Heart Lung and Blood Institute (NHLBI, 1998) identified a number of potentially effective weight loss interventions which include: reduction in sedentary behaviour in obese children; diet, exercise and behavioural strategies for adults, in combination where possible; the use of maintenance strategies; the use of pharmaceutical interventions in conjunction with strategies to change lifestyle; and surgery for selected morbidly obese patients.

Life style interventions Lifestyle interventions have been widely applied to obesity management. Restriction of calories and increased physical activity are central to most strategies for weight reduction (Nawaz & Katz, 2001). Although dietary recommendations may differ regarding fat, carbohydrates and protein intakes, it is agreed that a reduction in the total calorie intake is the key concept for weight loss (Noel & Pugh, 2002).

Although storing energy ‘Lifestyle interventions as fat is a defence mechanism that has facilitated have been widely applied the presence of human to obesity management. life on earth, nowadays Restriction of calories daily lives require minimal energy expenditure. and increased physical There have been imporactivity are central to tant changes in lifestyle leading to a progressive most strategies for weight decline in the necessary reduction’ physical activity in developed societies. Strong evidence indicates that increased physical activity results in modest weight loss and increases cardiovascular fitness independent of weight loss (Expert Panel, 1998). The Health Development Agency has noted that the commonly accepted view is that physical activity combined with diet is more effective than either diet or physical activity alone in producing weight loss (Mulvihill and Quigley, 2003). This is echoed in the executive summary of the clinical guidelines (Expert Panel, 1998) which recommended lifestyle strategies which combine controlled energy intake and increased physical activity as the most successful treatment for weight loss and maintenance of that weight loss. Additionally NICE (2006) has recommended the inclusion of behaviour change to bring about improvements in physical activity levels and diet in weight management programmes.

Pharmacological interventions Pharmacotherapy has also been demonstrated as effective in obesity management (Arterburn & Noel, 2001). A systematic review concluded that pharmacologic weight loss interventions as well as dietary/lifestyle interventions

Potential benefit of 10kg weight loss from initial 100kg weight in a patient with obesity related co-morbidities Event

Decreased risk of event (%)

Mortality Total mortality Diabetes related death Obesity related cancer deaths

30 30 40

Diabetes Fasting blood glucose HbA1c

50 15

Blood pressure 10mmHg systolic 20mmHg diastolic

10 20

Lipids Total cholesterol Triglycerides LDL HDL

10 30 15 8*

*An increase which is desirable Source: Jung 1997

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TOPIC HEADER result in modest weight loss, and may also improve markers of cardiovascular risk factors (Douketis et al, 2005). Both Orlistat and Sibutramine are licensed for use in England for the treatment of obesity in adults and it has been suggested that they need to be used in conjunction with healthy eating (Dept of Health, 2006). Drug therapy, therefore, should be considered as an addition (that is, as supplementary) rather than an alternative to lifestyle intervention. Furthermore, O’Meara et al (2000) have noted that the observed benefits of these weight loss drugs may not always be clinically significant and must be balanced against possible adverse effects (eg gastrointestinal disturbances, risk of pulmonary hypertension and severe cardiac vascular damage). The NICE (2001) has also recommended that such treatments should not usually continue beyond 12 months, and never beyond 24 months. Thus pharmacological interventions may have limited benefits for weight management over the long-term.

Surgical interventions Surgery may be considered in extreme cases of obesity where there is a BMI above 40 or above 35 with comorbidities. Surgery comprises a restrictive procedure that induces early satiety (for example, vertical banded gastroplasty, gastric banding) or a diversionary procedure that decrease caloric absorption (eg gastric bypass surgery). It is also suggested that access and support regarding lifestyle changes, particular in diet, should be arranged for patients after surgery (Dept of Health, 2005). In general the weight loss associated with surgical interventions is greater than that achieved by non-surgical methods. However, NICE (2006) noted that surgery is only recommended if all appropriate and available non-surgical measures have been adequately tried but failed to maintain weight loss for a least 6 months because the safety and effectiveness of surgical interventions remains uncertain. The potential operative, peri-operative, and long-term complications limit the recommendation of its wider application, despite the effectiveness of surgery in reducing weight in people with severe obesity (Noel & Pugh, 2002). It has also been reported that surgical procedures only produce weight loss and substantial metabolic improvement in the short term and should only apply to adults with morbid obesity because of the risks (Watkins et al, 2003). The cost of surgery and its impracticality limit the merits of a surgical approach in a long-term weight management for the obese population more generally. Among the mainstream of strategies for obesity treatment, it is clear that diet and lifestyle changes remain the first-line management for obese adults and include reducing calorie intake, increasing physical activity while reducing sedentary behaviours, and increasing self-awareness about day-to-day behaviours that affect intake and activity levels (Dept of Health, 2006).

Weight loss in diabetes care Weight loss reduces obesity related complications significantly, particularly for those with Type 2 diabetes.Therefore



weight loss should be one of the cornerstones of Type 2 diabetes management. There is no exception for weight reduction in diabetes care with lifestyle interventions offering the greatest hope of reducing the risk of cardiovascular disease associated with insulin resistance (McAuley et al, 2005).They are therefore an important component of any strategy for weight reduction as part of diabetes clinical management. Brown et al (1996) examined the effectiveness of weight loss interventions in obese patients with Type 2 diabetes across 89 studies using a meta-analysis. They found that diet had the largest statistically significant impact on weight loss (-20 lb) and metabolic control (2.7% in HbA1c) over the short term but there were few studies testing the effects up to 12 months. The Finnish Prevention Study (Tuomilehto, 2001) reported that changes in lifestyle including low fat, increased fibre intake and increased physical activity resulted in significant weight loss in the intervention group with 2 year follow up (year 1 was 4.2±5.1 kg and year 2 was 3.5±5.5 kg, p