Obesity and diabetes

Obesity has reached epidemic proportions in the developing world, and excess body weight is now the most common childhood disorder in Europe. In childhood and adulthood, excess weight can cause dyslipidaemia, hyperinsulinaemia and hypertension. Adult obesity is known to increase the risk of cardiovascular disease and diabetes, and in 2001, the first obesity-related cases of type 2 diabetes in adolescents were reported¹.

In 1998, more than a fifth of 13- to 16-year-olds in England were overweight or obese, and the National Diet and Nutrition Survey of 2000, which examined the diets of British school children aged four to 18 years, found that adolescents ate more than the recommended level of sugar, salt and saturated fat. The most frequently consumed foods included white bread, savoury snacks, biscuits, potatoes and chocolate confectionery. The Health Survey for England 2001² found that less than 20 per cent of boys and 15 per cent of girls aged 13 to 15 managed to eat the recommended five or more portions of fruit and vegetables per day.

Weight gain and obesity are caused by an excess of calories consumed over energy expended. It is reasonable to suggest, therefore, that the nation?s obesity problem is due to a combination of physical inactivity and high-energy diets. Obtaining a balance between intake and output is important in all individuals, but particularly in diabetics, and recent data suggest that it is possible to prevent type 2 diabetes in high-risk individuals using weight management³.

Obesity is defined as a body mass index of greater than 30kg/m². In the nurses? health study⁴ the risk of type 2 diabetes in women with an index of 29-31 was 28 times greater than in women with an index lower than 22. A BMI greater than 35 increases the risk of diabetes 93-fold.

Another study, involving 84,941 female nurses, found that modifiable risk factors related to diet, weight and physical activity could reduce the risk of developing diabetes by as much as 91 per cent. Even when there was a strong family history of diabetes, the risk reduction was 88 per cent.

What is a healthy diet for diabetics?

A healthy diet for a person with diabetes is essentially identical to the healthy diet recommended for everyone. Although diabetic patients must ensure that they control their blood sugar, they need not be restricted to a sugar free diet. Diabetics used to be advised to restrict the use of sugar and sugary foods, but it is now known that sugary foods do not raise the blood glucose levels any higher than do starchy foods containing the same calories. Therefore, sugar can be eaten as part of a balanced, healthy diet without having a harmful effect on glycaemic control.

Diabetes UK?s current advice is that sugar can be used by people with diabetes who are not overweight, provided that it is used in the context of a healthy diet and does not account for more than ten per cent of the calories obtained from carbohydrate. This is in line with recommendations for the general population.

Foods marketed as “suitable for diabetics”, which generally contain a nutritive sweetener in place of sucrose, are as high in fat and calories as standard products, and often more expensive, and the remark of Benet Middleton, CEO of Diabetes UK at the Obesity 2003 seminar that “diabetic foods are not the answer; diet change is” sums up the general attitude towards them.

In 2002, Diabetes UK and the Food Standards Agency condemned diabetic foods, describing them as overpriced and of no real benefit for people with diabetes. And, according to Sir John Krebs, chairman of the FSA: “Labelling confectionery and biscuits as ?suitable for diabetics? undermines advice to people with diabetes to eat a healthy diet, high in carbohydrates like cereals, pasta, rice and bread, including vegetables and fruit, but low in fat.”

More recently, the Atkins diet ? low in carbohydrate and high in protein ? has received a great deal of attention for promising to help people lose pounds quickly without feeling hungry. However, there is a general lack of good research comparing this diet with the conventional low-fat, high-carbohydrate diets. A study published in the New England Journal of Medicine showed that a low-calorie, low-carbohydrate, high-protein diet produces weight loss that is rapid in comparison with the speed of weight loss achieved with a low-calorie, high-carbohydrate, low-protein diet, but in the longer term outcomes (weight loss and keeping weight off) were comparable.

Diabetes UK is currently funding research to look into the long-term health effects of low-carbohydrate diets. Other studies have suggested certain foods, such as cinnamon⁵, may be of benefit to diabetic patients, but the evidence base tends to be small. It is most sensible, therefore, to recommend a healthy, balanced diet that the patient is likely to be able to follow for the rest of their life.

This should include eating regular meals based on starchy foods such as bread, pasta, potatoes, rice and cereals. According to the European Association for the Study of Diabetes (EASD) and the American Diabetic Association (ADA), carbohydrate should make up between 40 and 65 per cent of energy intake, a level which will help control blood glucose levels. A good selection of high fibre varieties of foods like granary bread and wholegrain cereals should be included.

Cutting down on sugar and sugary foods will also aid weight loss, but this does not mean sugar has to be excluded completely. Diabetics can still eat sugar but it should not exceed ten per cent of the daily energy intake.

Eating less saturated fat and fatty foods will help weight loss and reduce cardiovascular risk. Total fat intake should make up less than 35 per cent of the total energy intake and should ideally be in the form of monosaturates because of their lower atherogenic potential.

The EASD and the ADA recommend that very low calorie diets (less than 800Kcal per day) should only be considered in patients with a BMI greater than 35 and in conjunction with a structured weight management programme.

According to draft diabetes guidelines from the National Institute for Clinical Excellence (NICE), children with type 1 diabetes should be encouraged to consider a bedtime snack for euglycaemia. The nutritional composition and timing of all snacks should be discussed with the diabetes care team.

Moderate alcohol consumption (two to three units per day on average) around meal times should not affect short-term glycaemic control, but is calorific.

Hypo- and hyperglycaemia may occur when a patient modifies their diet. It is important to adapt insulin dosage (or oral hypoglycaemic use) accordingly. Preliminary results from the insulin dose adjustment for normal eating (DAFNE)⁶ trial suggest skills training in insulin adjustment enables patients to achieve good glycaemic control even when dietary intake varies. The participants who followed the regimen had significantly improved HbA1c levels with no significant hypoglycaemia, weight gain or increase in blood lipids.

How much weight loss?

A thorough assessment is required to determine what dietary and exercise advice a patient will need.

The patient?s BMI can be calculated to work out how overweight they are, with anything over 25 too high and below 20 too low. Diabetes UK also recommends measuring waist circumference (measure half way between the lowest point of the rib cage and the iliac crest). In Caucasians, a waist circumference of 102cm or greater in men and 88cm or greater in women predicts risk of disease associated with obesity⁷.

The healthcare professional should gain some insight into the patient?s background and lifestyle. Ask about their typical eating pattern (i.e. which foods they eat and how frequently and at what times of the day), alcohol consumption, exercise, smoking, emotional state and their willingness to modify their lifestyle. Also ? check their general health status (blood pressure, lipids etc), their glycaemic control, insulin/orohypoglycaemic requirements and ask about any other health problems.

The skill is in tailoring the weight management strategy to the individual. One pound in weight, or 0.45kg, is equal to about 3,200 calories. Therefore, a person consuming 500 more calories than he or she expends per day will gain 0.45kg per week.

Evidence-based guidelines (SIGN and NIH) suggest that weight gain be restricted first. There should then be a two to three month period of weight loss with the goal of shedding five to ten per cent of total body weight. For a person with a BMI 27-35, this would mean they should lose 0.25-0.5kg per week at a daily calorie deficit of 300-500.

Diet alone is not helpful in the long term – more than 90 per cent of people who attempt to lose weight regain it. Exercise should also be used.

The American College of Sports Medicine recommends 30 minutes of moderate intensity activity (such as brisk walking) at least five days per week to reduce the risk of diabetes, cardiovascular mortality and all-cause mortality – equivalent to 1,000kcal burnt.

However, Professor Ian Macdonald, professor of metabolic physiology at the University of Nottingham, believes this is not enough for weight control. He recommends 45-60 minutes of activity per day to prevent the progression from overweight to obese, and more than 90 minutes on most days to prevent weight regain in obese patients.

Diabetes UK advises that exercise should be postponed if the blood glucose concentration is above 15mmol/l or if there is ketonuria. There is considerable individual variation in the response to exercise, therefore it is important that patients monitor their blood glucose before and after exercise and have immediate access to rapidly absorbed carbohydrates (eg 55 ml of a high-energy glucose drink or 100 ml of cola) should hypoglycaemia occur. Exercise tends to induce hypoglycaemia, but this can be avoided by planning exercise sessions and reducing the dose of insulin or oral hypoglycaemic agent before activity. Further dose reductions and additional food may be needed after intensive exercise.

The NICE draft guidelines advise that children with type 1 diabetes, their parents, and other carers, be informed that exercise should be undertaken with caution if blood glucose levels are greater than 17 mmol/l, even if ketosis is not present. Additional carbohydrate should be consumed if blood glucose levels are less than 7 mmol/l, it adds.

Certain patient groups will need special attention. Nutritional requirements change throughout childhood and adolescence, and children should ideally be seen by a specialist paediatric dietician. Catching diabetes and obesity early is crucial to successful long-term outcomes.

Pregnant women will also need careful monitoring. Optimal diabetic and weight control is desirable before conception. Pregnancy can also induce diabetes in women who have previously been unaffected. Insulin requirements and weight will change as pregnancy progresses, and both should be regularly monitored.

As diabetes is more common in people of south Asian, Caribbean and West African origin, religious and cultural dietary preferences should be taken into consideration when forming a management plan.

How to achieve weight control ? the multidisciplinary approach

Both the Diabetes Control and Complications Trial (DCCT) ⁸ and the UK Prospective Diabetes Study (UKPDS) ⁹ demonstrate the value of dietetic intervention from diagnosis onwards.

Diabetes UK recommends people with diabetes should see a state registered dietitian at diagnosis for specific advice on their diet based on their individual needs, while its survey of dietitians working in diabetes care in 1997¹⁰ revealed 85 per cent worked in situations where dietetic provision was less than the recommendation made by the charity in 1999. Only 69 per cent reported seeing more than half of newly diagnosed adult patients within four weeks of diagnosis.

It is estimated that at least 80 per cent of newly diagnosed patients with type 2 diabetes are overweight. These patients need more than one or two dietetic consultations in the first six months of diagnosis if they are to achieve clinically significant weight loss.

All people with diabetes should have ongoing access to dietetic advice and support. In the short term, food intake needs to be regulated and balanced against medication, in order to optimise blood glucose control. This includes assessment of whether current medication matches the meal pattern and therefore whether it is appropriate, as well as management and prevention of hypoglycaemia and hyperglycaemia. Long-term dietary control can offer protection against cardiovascular disease, with weight management and modification of other lifestyle factors being essential.

Care should be multidisciplinary and integrated, involving hospital specialists, GPs, practice nurses, dieticians, health visitors, schools, parents and most importantly the patient.

The Diabetes National Service Framework (NSF)¹¹ emphasises the importance of nutrition and dietetic advice. Standard ten says “all young people and adults with diabetes will receive regular surveillance for the long-term complications of diabetes” and standard 12 that “all people with diabetes requiring multi-agency support will receive integrated health and social care”.

By March 2006, primary care organisations will be expected to have updated their practice registers so patients with diabetes (and coronary heart disease) continue to receive appropriate advice and treatment. This includes appropriate advice on diet and physical activity.

The NSF also says care should be delivered by clinically-led, managed diabetes networks, comprising PCTs, NHS trusts, clinical champions and strategic health authorities but to name a few.

The future

Two antiobesity agents ? silbutramine and orlistat ? are available in England and Wales on the recommendation of NICE. It says orlistat should be available as one part of the management of obesity for adults who have lost 2.5 kg by diet and increased activity in the month prior to their first prescription and who have a body mass index of 28 kg/m² or more and another serious illness that persists despite standard treatment (for example, Type 2 diabetes, high blood pressure and/or high cholesterol). Exercise-on-prescription is being developed in the UK.

The diabetes NSF highlights initiatives to improve diabetes care. The Five-a-day Programme for fruit and vegetables aims to increase consumption, particularly in deprived groups. It is hoped that the National School Fruit Scheme will ensure that every child in nursery and aged four to six in infant schools gets to a free piece of fruit each day at school.

The government has also devoted funding to school PE and sports programmes and nine community pilots for increasing physical activity in children and adults.

In January 2004, the NHS launched its first weight-loss clinic for children aged 11 to 17, based in Walsall in the West Midlands. The clinic will open once a month for a year and will focus on play, activity and family eating.

References

1 Drake AJ et al, Archives of Disease in Childhood 2002; 86: 207-208 565-571

11 Department of Health 2001

Dr Michelle Roberts is a freelance medical writer. This feature first appeared in the March 2004 edition of Nutrition Review