Dr Deirdre Carroll looks at the relationship between obesity and the development of type II diabetes and examines recent guidance on the management of obesity.
The prevalence of overweight and obesity has increased dramatically over recent decades to what has been described as epidemic proportions.
Some 38 per cent of Irish people are overweight and 23 per cent are obese (according to the National Survey of Lifestyle Attitudes and Nutrition 2007).
The rise in obesity is reflected in the rising incidence of type II diabetes. It is estimated that 200,000 people in Ireland have a diagnosis of diabetes and that there may be a further 100,000 who are unaware that they have it. Obesity and diabetes have the potential to severely impact the health of individuals, as well as impacting on the workforce, reducing productivity, increasing the pressure on and costs to the health service and the social welfare system.
The increasing rates of obesity and diabetes are multi-factorial. Over-eating and a sedentary lifestyle increase the risk of developing obesity and/or diabetes. Only 41 per cent of Irish adults take part in moderate or strenuous exercise for at least 20 minutes, three or more times a week. Genetic factors, low birth weight and possibly stress may also play a role.
In some patients, there are other contributory factors such as medications, e.g. atypical anti-psychotics, and conditions such as polycystic ovarian syndrome.
Biggest risk factor
Obesity is the single biggest risk factor for the development of type II diabetes. As body mass index (BMI) increases, the risk of type II diabetes increases in a dose-dependant manner by increasing insulin resistance. The prevalence of type II diabetes is three-to-seven times higher in obese adults than in normal-weight adults, and those with a BMI >35kg/m2 are 20 times more likely to develop type II diabetes than those with a BMI between 18 and 24.9.
Large waist circumference (WC) is another important risk factor for type II diabetes (>94cm in men and >80cm in women). The other risk factors are physical inactivity, previous gestational diabetes or ‘pre-diabetes’ (impaired fasting glycaemia or impaired glucose tolerance), family history of diabetes, increasing age, certain ethnicities (Asian, African, African Caribbean, Chinese descent), and being from a lower socio-economic group.
The more risk factors an individual has, the more likely they are to develop diabetes. Obesity and diabetes are important independent and additive cardiovascular risk factors. They both increase obstetric, perinatal and neonatal complications, raise certain cancer risks (e.g. colon) and are associated with an increased risk of dementia and renal disease and with higher mortality rates.
Obesity is also a known risk factor for asthma, depression, gastro-oesophageal reflux disease, reduced fertility, gallstones, osteoarthritis, liver disease and obstructive sleep apnoea.
In addition, there are the acute risks of diabetes (hypoglycaemia/ketoacidosis) and chronic problems of retinopathy and nephropathy. On average, at the age of 55 years, the life expectancy of people with type II diabetes is five-to-seven years less than for the general population.
Lifestyle interventions to improve diet and to increase the amount of physical activity in an individual with impaired glucose tolerance can more than halve their risk of going on to develop type II diabetes, as seen in the Diabetes Prevention Study.
Public health guidance
NICE has just published public health guidance for ‘Preventing type II diabetes: population and community-level interventions in high-risk groups and the general population’ (PH35 May 2011). It is aimed at a wide-ranging audience including GPs, practice nurses, dieticians, those involved in delivery of physical activity interventions, managers in the health service, national policy makers and also for caterers, food manufacturers and retailers.
Early intervention to prevent type II diabetes is important to prevent a range of non-communicable disease (including cardiovascular disease and some cancers). This guideline recommends both local measures to promote health and preventive measures, and national action to address the adverse environmental factors driving the increasing prevalence of type II diabetes.
It advises an integrated approach with other health promotion campaigns or interventions, and targeting those with shared risk factors.
In addition to this guideline, there is recent SIGN guidance ((CG115) Feb 2010) on the management of obesity. They share much of the same treatment advice:
-> Assessment. Classify the extent of obesity (and the risk of obesity-related co-morbidities) using BMI and waist circumference, seek a weight history and previous attempts to reduce weight as well as willingness to change;
-> Support behaviour change by helping people understand the consequences of health-related behaviour, helping them to plan for and feel positive about changing their behaviours and planning coping strategies for situations that may undermine the changes they are trying to make;
-> Achieve and maintain healthy weight. Base meals on starchy foods, eat fibre-rich foods and five portions of fruit and vegetables a day, eat a low-fat diet, watch calorie intake and portion sizes, and eat breakfast. If weight loss is required, dietary interventions should be calculated to produce a 600kcal/day energy deficit and tailored to the dietary preferences of the patient. Reduction of intake of energy-dense foods, consumption of ‘fast foods’ and alcohol. Adults consulting about weight management should self-weigh regularly;
-> Effective weight-loss programmes should be tailored to the individual, identify and address barriers to change. Expect people to lose no more than 0.5-1kg per week. Patients with a BMI over 35kg/m2 will usually need to lose 15-20 per cent of their weight for sustained improvement of co-morbidities. In patients with a BMI of 25-35kg/m2, obesity-related co-morbidities are less likely to be present and a 5-10 per cent weight loss (approximately 5-10kgs) is required for cardiovascular and metabolic risk reduction. People from some ethnic groups, e.g. South Asians develop co-morbidities at lower BMI;
-> Physical activity. To achieve general health benefits, one should accumulate at least 30 minutes of moderate-intensity physical activity on at least five days per week. To lose weight, most people need to do at least 45-60 minutes of moderate-intensity activity a day; people who have been obese and have lost weight may need to do 60-90 minutes of activity a day to avoid regaining weight. They should make activities they enjoy part of their routine, e.g. walking, cycling and gardening, and build in activity where possible, e.g. always take the stairs, fit in a walk at lunchtime and minimise sedentary activities, e.g. sitting in front of the television or computer;
-> Interventions should be culturally appropriate to take into consideration the person’s cultural or religious beliefs and language and literacy skills.
Orlistat is the only licensed obesity drug available, to be used as an adjunct to lifestyle interventions. It should only be continued beyond 12 weeks if 5 per cent of the body weight has been lost. The XENDOS study showed a reduction in progression to diabetes in those on orlistat by 37 per cent.
Bariatric surgery should be considered in those with a BMI >35kg/m2 who also have severe co-morbidity which would be expected to improve following weight loss (e.g. diabetes, arthritis, severe mobility problems). They should also have evidence of completion of a structured weight management programme without significant and sustained improvement in their co-morbidities.
Children and young people
Obesity is the most common chronic disorder in childhood and is increasing in prevalence (a 2007 study estimated that one in four Irish children are overweight or obese). It is associated with hypertension, increased cardiovascular risk, metabolic syndrome and psychosocial problems. Obese children are at high risk of becoming obese adults and have a worse prognosis than adults who become obese in later life.
For the assessment, it is recommended that the BMI is calculated and plotted on centile charts. A BMI above the 91st centile for age indicates overweight and above the 98th indicates obesity.
The principle recommendations in the SIGN guideline are as for adults, but also state that interventions should be family-based, involving at least one parent/carer, aim to change the whole family’s lifestyle and reduce sedentary behaviour to less than two hours per day or 14 hours per week (‘screen-time’).
The treatment of obesity and diabetes are closely linked: obesity complicates the management of type II diabetes by increasing insulin resistance and blood glucose concentrations. The situation is further complicated by the fact that certain diabetes treatments are associated with weight gain (insulin, sulphonylureas and thiazolidinediones). Therefore, weight reduction interventions are an integral part of diabetes management.
On the other hand, GLP-1 agonists may be beneficial in weight reduction as well as glycaemic control.
Benefits of treatment
Weight reduction has been shown in overweight or obese adults with diabetes to improve glycaemic control and reduce the requirement for glucose-lowering medication, as well as lowering all-cause mortality. Weight loss in obese individuals has also been associated with reductions in blood pressure, lipid profiles, arthritis-related disability, lower mortality from cancer and improved lung function in patients with asthma.
Physical activity or structured exercise programmes for type II diabetics improve glycaemic control and cardiovascular risk factors, even in the absence of weight loss.
Structured diabetes education programmes such as X-PERT, CODE and DESMOND have shown good results in terms of patients’ knowledge and self-management, and X-PERT has been shown to effect a 0.6 per cent reduction in HbA1c.
Given the rising prevalence and impact of these conditions, obesity and diabetes are issues for all health professionals to address. However, as stated in the recent NICE guideline (PH35), the greatest impact on the levels — and associated costs — of type II diabetes is likely to be achieved by addressing the risk factors in whole communities and populations.