CHAPTER 2 LIFESTYLE
Diabetes mellitus is the epitome of a chronic disease in which the goals and management extend beyond purely medical interventions “owned” by a clinician. Although “patient empowerment” has acquired more than a whiff of political correctness, it is, nevertheless, at the centre of diabetic management: the patient “owns” his disease and his lifestyle can have a major effect on morbidity and mortality.
Since lifestyle is a collection of behaviours, interventions by health-care professionals will be based upon providing suitable and effective health education. The patient’s concordance with well-meant guidance depends upon persuasion that any change in his behaviour will be in his self-interest.
The components of lifestyle discussed in this section can affect morbidity and mortality not just in diabetics but in the general population. Many of the concepts and interventions discussed below may be appropriate in a non-diabetic population.
Diabetics no longer require a separate diet with special food products: a “healthy” diabetic diet suits most of the general population, particularly when the modification of cardiovascular risk is a priority. MNT involves balancing complex issues and needs, tailored to the lifestyle, cultural and religious customs, and to the patient’s overall diabetes management.
Information gathering about diet should not be restricted to current behaviour, but should also enquire about willingness and barriers to change. An assessment may involve questioning both the patient and other members of the household, and from reviewing a food diary which the patient may be asked to keep.
In 2003 Diabetes UK issued a comprehensive list of consensus-based recommendations for diabetics that drew upon many sources to provide detailed practical advice for professionals to implement (Connor et al 2003). These are summarised in Table 2.1. The American Diabetes Association has also published its recommendations in its annually updated guidance.
|Protein||Not > 1 g per kg body weight (different for nephropathy and children)|
|Total fat||< 35% of energy intake|
|Saturated + transunsaturated fat||< 7% of energy intake with trans fat intake minimised|
|n-6 polyunsaturated fat||< 10% of energy intake|
|n-3 polyunsaturated fat||Eat fish, especially oily fish, 1–2 times weekly|
|Fish oil supplements not recommended|
|Sucrose||Up to 10% of daily energy, eaten within the context of a healthy diet|
|Consider using non-nutritive sweeteners where appropriate if overweight and/or hypertriglyceridaemic|
|Fibre||No quantitative recommendation|
|Soluble fibre has beneficial effects on glycaemic and lipid metabolism|
|“Insoluble” fibre has no direct effects on glycaemic and lipid metabolism, but its high satiety content may help weight loss and is advantageous to gastrointestinal health|
|Vitamins and antioxidants||Encourage foods naturally rich in vitamins and antioxidants|
|Supplements are usually not recommended (except in special circumstances) and some may be harmful|
|Salt||< 6 g sodium chloride per day|
Central to MNT must be changes in the patient’s behaviour. Crucial to helping to bring about change is an understanding of various aspects of health education, discussed in detail later in this section.
Diabetes dietetic advice should emphasise the need to space regular meals and snacks appropriately throughout the day. This will spread nutrient intake and avoid hypoglycaemia. If the daily energy intake is appropriate, the frequency of meals is not critical; however, dieticians advise eating at regular intervals and not undergoing prolonged spells without food: avoiding a “feast or famine” eating pattern. By making the mealtime an occasion to enjoy and savour food, patients may avoid abstractly consuming (possibly excess quantities of) food while focused upon another activity. Patients should be warned to avoid special diabetic products, which are often expensive and with a high fat content.
Due to recent concerns about the accuracy of food labelling in the UK, shoppers do need to pay close attention to the information provided on labels and to not accept blindly adjectives such as “healthy”, “low”, “high” or “restricted”.
To achieve a slow and progressive weight loss (1 to 2 kg per month), structured dietary advice (based upon the assessment) should be guiding and supporting the patient to make eating choices that produce a sustained energy deficit of 500 to 1000 kcal per day. These need to be tailored to the patient’s own needs and preferences and combined with increased levels of physical activity.
Most people eat a fairly consistent volume of food from day to day, irrespective of its energy content. Reducing significantly total quantities may be difficult. It is better to focus upon reducing the energy content of this bulk (dietary energy density, expressed as kcal per 100 g or 100 ml of food), allowing a sufficient amount of food to be consumed for satiety, but with a lower energy yield.
Probably the most important change is to replace fat-rich foods and other dietary fat sources with starchy carbohydrate foods, maintaining nutrition. Alcohol contains 7 kcal/g, and should be restricted in a weight management programme.
The carbohydrate intake should comprise 45–60% of total calories, but the proportion may vary according to individual factors, such as age, activity levels and weight. The total carbohydrate consumed should not normally be less than 130 g per day, since the brain and central nervous system have a minimum requirement for glucose as an energy source.
Reducing the total quantity of carbohydrate consumed is the basis of producing an energy deficit of between 500 and 1000 kcal/day. Very low calorie diets (VLCD) are defined as containing less than 800 kcal/day and are designed to produce more rapid weight loss in very obese individuals (BMI greater than 35 kg/m2). However, there is no evidence that they produce better long-term results and should only be used under careful specialist supervision with close attention paid to glycaemic control and nutritional maintenance.
The terms sugars, starch and fibre are preferred to the terms simple sugars, complex and fast-acting carbohydrates, as the latter are not well defined. The glycaemic index (GI) has been devised to quantify the glycaemic effect of different foods. However, different methods of food processing and preparation, and ripeness in some cases, can alter the GI. Consuming food with a low GI has not been shown to improve glycaemic control in type 2 diabetics, but may improve the lipid profile. However, using the GI may provide additional benefit for glycaemic control beyond that observed for carbohydrate monitoring alone (ADA 2007).
Fibre-containing foods, such as whole grains, fruit and vegetables, provide vitamins, minerals and other important substances, and should be included in the diet. However, very large amounts of fibre would need to be consumed to produce metabolic improvements on glycaemia and lipid profiles. Sucrose or sucrose-containing foods should not be restricted for diabetics, but can be used in substitution for other carbohydrate sources.
Protein is an essential nutrient that provides amino acids for new tissue formation. Protein intake should constitute 15 to 20% of the total energy intake (optimally 0.8 g/kg body weight/day). Moderate hyperglycaemia can cause increased protein turnover, but, since most adults eat at least 50% more protein than required, intake should not be increased to compensate.
Both Diabetes UK (Connor et al 2003) and the National Cholesterol Education Program (Expert Panel 2001) recommend that the total fat should not exceed 35% of the total energy intake. The most important dietary modification is to reduce the intake of saturated fat, the principal dietary determinant of serum LDL-cholesterol levels; saturated and transunsaturated fat should provide less than 7% (ADA 2007) or 10% (Connor et al 2003) of energy. Unfortunately, in most European countries, current intake of saturated fat is above the recommended maximum 10% of total energy intake.
Sterols and stanols of plant origin have been shown to reduce serum LDL-C levels, and are now incorporated into spreads and other fat-derived products, such as yoghurts, semi-skimmed milk, cereal bars and soft cheeses. These are marketed as adjuncts to other methods of lowering LDL-cholesterol. However, the spreads are markedly more expensive than conventional margarines, their effect on long-term cardiovascular morbidity and mortality is unknown, and their benefits may be offset by reductions in fat-soluble vitamin absorption and in plasma concentrations of the antioxidants β- and α-carotene and vitamin E. Furthermore, they may not reduce total energy intake or weight.
As with the general population, diabetics should benefit from consuming a range of foods containing fibre, such as fibre-rich cereals (more than 5 g of fibre/serving), fruits, vegetables and whole-grain products. These are sources of vitamins and minerals.
Diabetics should be aware of both the importance of consuming adequate quantities of vitamins and minerals from natural sources and the potential toxicity of very large doses of these in supplements. Supplementation is indicated only in selected patient groups (e.g. elderly, those on restricted calorie diets and those with proved deficiency). Although diabetics may be in a “state of increased oxidative stress”, there is no placebo-controlled trial evidence of benefit of antioxidant vitamin supplementation.
Reduced calorie sweeteners available include sugar alcohols (erythritol, hydrogenated starch hydrolysates, isomalt, lactitol, maltitol, mannitol, sorbitol and xylitol) and tagatose. If undertaking calorie counting, then one can subtract one-half of sugar alcohol grams from total carbohydrate grams. There is no evidence that consuming sugar alcohol will reduce energy intake significantly or improve glycaemic control over the long term.
The standard advice is: to stay within the recommended limits and to avoid drinking on an empty stomach (risk of significant hypoglycaemia) or as a substitute for a meal. In type 2 diabetics, drinking two to three glasses of wine (or the equivalent quantity of beer) may produce an insignificant drop in blood glucose, but does not increase the risk of hypoglycaemia (Christiansen et al 1996). Alcohol is potentially a major energy source, but it can contribute to elevated blood pressure and serum triglycerides.
The American Dietary Approaches to Stop Hypertension (DASH) is an eating plan that advises hypertensive individuals to consume a diet rich in fruit, vegetables and low-fat dairy products with a reduced content of saturated and total fat. Those who follow this diet combined with sodium restriction can expect to their lower systolic blood pressure by 8 to 14 mmHg (Sacks et al 2001). The eating plan can be downloaded off the internet.
Although there appears to be an inverse relationship between blood pressure levels and the consumption of potassium (found in fruit and vegetables), magnesium and calcium, the 2004 BHS guidelines do not recommend supplementation of these minerals.
The professional needs to tailor the advice given within the bounds of what is acceptable, attractive and realistic. Different Indo-Asian diets are suitable, provided that total fat intake is reduced. The manner in which food is prepared is important. While patients are encouraged to substitute olive oil for ghee in cooking, quantities should be measured and minimised.
Practice nurses and GPs are ideally placed to provide the basics of sound nutritional advice and should reinforce this as appropriate when reviews are undertaken. However, a referral to a qualified dietician for an individual dietary assessment is appropriate:
A sedentary lifestyle is associated with an increased risk of coronary heart disease (CHD). Sedentary individuals are more likely to be obese and have adverse lipid profiles. In one study that recruited diabetic women, those undertaking less than 1 hour per week or no physical activity doubled their risk of having a cardiovascular event, compared to those undertaking at least 7 hours per week of physical activity (Hu et al 2001). Another study that recruited diabetic men found that “low” baseline cardio-respiratory fitness nearly trebled overall mortality compared with “moderate” or “high” fitness, and overall mortality nearly doubled in those reporting no recreational exercise in the previous 3 months, compared to those reporting any recreational physical activity in the same period (Wei et al 2000).
There is no current evidence to demonstrate a direct relationship between levels of physical activity and the development of the macrovascular and microvascular complications of diabetes. The arguments in favour of increased physical activity are based upon extrapolation from the effect of exercise on glycaemia. A recent report by the Chief Medical Officer distinguishes between the preventive effects (which appear to be strong) and the therapeutic effects of physical activity in type 2 diabetics (Department of Health 2004). The key message is that “the correct type of exercise is good”.
Exercise has both short- and long-term benefits in type 2 patients (see Table 2.2). Exercise can be an effective way to reduce the risk of cardiovascular disease (CVD) (Pierce 1999): an appropriate level of physical activity, particularly in conjunction with diet, can improve cardiovascular risk factors, such as blood pressure, weight and lipids. A Cochrane meta-analysis of 14 RCTs “showed that exercise … improves glycaemic control and reduces visceral adipose tissue and plasma triglycerides, but not plasma cholesterol, … even without weight loss” (Thomas et al 2006).
|Reduced short-term insulin resistance; long-term effect has yet to be established|
|Increased peripheral glucose uptake|
|Less atherogenic profile (decreased triglycerides and LDL cholesterol with a beneficial increase in HDL cholesterol)|
|There is still no clear consensus on whether physical training results in improved fibrinolytic activity, which is impaired in type 2 diabetics|
|Reduces hypertension, particularly when hyperinsulinaemia is present|
|Helps to maintain muscle mass and promote preferentially the loss of adipose tissue, which may reduce the fall in metabolic rate during slimming and accelerate long-term weight loss|
|Favours weight loss by increasing energy expenditure (although an ageing overweight type 2 diabetic will be hard pressed to maintain the necessary daily level of exercise), in combination with a “slimming” diet|
Prevention: physical activity undertaken in early adult life protects against the subsequent development of type 2 diabetes in middle-aged men and women (Ha & Lean 1997) and in patients with impaired glucose tolerance (Tuomilehto et al 2001)
Most diabetics should seek to be more physically active. The type and level of physical activity undertaken on a regular basis should be appropriate and enjoyable to the individual, and should promote endurance, muscle strength and flexibility – reducing cardiovascular risk.