Diabetes diet and exercise

Interventions aimed at increasing exercise, combined with diet have been shown to decrease the incidence of type 2 diabetes mellitus in high-risk groups (people with impaired glucose tolerance or the metabolic syndrome).¹ However, there are currently no high-quality data to support dietary intervention alone for the prevention of type 2 diabetes. Exercise appears to improve glycated haemoglobin at six and twelve months in people with type 2 diabetes.²

Nutritional advice and information are essential for the effective management of type 1 diabetes. Exercise reduces mortality in type 1 diabetes and can reduce HbA1c by 0.7% in type 2 diabetes.³

Dietary advice

See also the separate Healthy Diet Advice and Enjoyable Eating article. The goals of dietary advice are:

• To maintain or improve health through the use of appropriate and healthy food choices.

• To achieve and maintain optimal metabolic and physiological outcomes, including:
  

  • Reduction of risk for microvascular disease by achieving near normal glycaemia without undue risk of hypoglycaemia.

  • Reduction of risk of macrovascular disease, including management of body weight, dyslipidaemia and hypertension.

• To optimise outcomes in diabetic nephropathy and in any other associated disorder.

Diabetes UK recommendations³

• Eat three meals a day. Avoid skipping meals and space breakfast, lunch and evening meal out over the day.

• At each meal include starchy carbohydrate foods - eg, bread, pasta, chapatis, potatoes, yam, noodles, rice and cereals. Eat more slowly absorbed (low glycaemic index) foods - eg, pasta, basmati or easy cook rice, grainy breads such as granary, pumpernickel and rye, new potatoes, sweet potato and yam, porridge oats, All-Bran® and natural muesli.

• Reduce the fat in the diet, especially saturated fats. Use unsaturated fats or oils, especially mono-unsaturated fats - eg, olive oil and rapeseed oil.

• Eat more fruit and vegetables. Aim for at least five portions a day.

• Eat more beans and lentils - eg, kidney beans, butter beans, chickpeas or red and green lentils.

• Eat at least two portions of oily fish a week - eg, mackerel, sardines, salmon and pilchards. Limit sugar and sugary foods.

• Reduce salt in the diet to 6 g or less per day.

• Drink alcohol only in moderation.

• Don't use diabetic foods or drinks (they are expensive and of no benefit).

Type 2 diabetes⁴

• Encourage high-fibre, low glycaemic index sources of carbohydrate in the diet, such as fruit, vegetables, whole grain and pulses. A low glycaemic index diet can improve glycaemic control in diabetes without compromising hypoglycaemic events.⁵

• Include low-fat dairy products and oily fish. Control the intake of foods containing saturated and trans fatty acids.

• include other aspects of lifestyle modification, such as increasing physical activity and losing weight.

• For adults with type 2 diabetes who are overweight, set an initial body weight loss target of 5%. Lesser degrees of weight loss may still be of benefit, and larger degrees of weight loss in the longer term will have advantageous metabolic impact.

• Limited substitution of sucrose-containing foods for other carbohydrate in the meal plan is allowable but excess energy intake should be avoided. Discourage the use of foods marketed specifically for people with diabetes.

• Dietary advice should be personalised and take on board the individual's needs, culture and beliefs, and willingness to make changes. Advice should be ongoing and available educational programmes should be offered - eg, DESMOND (= Diabetes Education and Self-management for Ongoing and Newly Diagnosed.)⁶

Low or very low carbohydrate diets

There is still some debate over the role of low carbohydrate diets in the management of diabetes. Currently there is insufficient evidence about safety or efficacy to recommend the long-term use of low (or very low) carbohydrate diets for people with diabetes.⁷

Diabetes UK advises that low carbohydrate diets (containing 50-130 g carbohydrate) are effective in the short term for managing weight and glycaemic control in overweight or obese people with type 2 diabetes.⁸ There is no strong evidence to recommend them for people with type 1 diabetes.

Type 1 diabetes

• Diet should be assessed with a view to reducing hypoglycaemia in all people with diabetes whose treatment includes insulin. The hyperglycaemic effects of different foods should be discussed in the context of the insulin preparation chosen to match the patient's food choices.

• Educational programmes - eg, DAFNE (= Dose Adjustment For Normal Eating ).⁹ These should be available so that patients can make an educated choice about:
  

  • The variety of foods they wish to eat.

  • Insulin dose changes appropriate to reduce changes in glucose levels when eating different amounts of those foods.

  • The type and amount of snacks taken between meals and at bedtime - discussed in the context of the patient's insulin regime. Those choices may need to be adjusted according to the individual's self-monitoring tests. Advise snacks only if self-monitoring suggests a need; check particularly if a high insulin analogue dose is needed to correct preprandial hyperglycaemia.

• Patients should be made aware of:
  

  • The effects of different alcohol-containing drinks on blood glucose excursions and calorie intake.

  • The use of high-calorie and high-sugar 'treats'.

  • The use of foods of high glycaemic index.

The National Institute for Health and Care Excellence (NICE) recommends that the nutritional advice given to insulin-dependent patients may need to be modified to take into account patients who are underweight, have eating disorders, have hypertension or have chronic kidney disease. The information made available to people with type 1 diabetes should consider cultural and religious diets, feasts and fasts and should include matching carbohydrate, insulin and physical activity.¹⁰

Exercise³

• Regular physical activity improves insulin resistance and lipid profile (reduction in triglyceride and increase in high-density lipoprotein (HDL)) and lowers blood pressure (BP), although BP will rise during exercise.

• The metabolic benefits in type 2 diabetes are lost within 3-10 days of stopping regular exercise.

• Physical activity also protects against the development of type 2 diabetes.

Diabetes UK recommendations¹¹

• The recommended minimum amount of activity for:
  

  • Adults - 30 minutes on at least five days of each week.

  • Children - one hour each day.

• It is essential to find activities that are enjoyable, achievable and sustainable - eg, walks, dancing, swimming, bowling, cycling, golf, playing with the children, DIY.

Special considerations when advising those with diabetes about exercise¹²

• Always consider insulin/oral hypoglycaemic therapy and meal schedule: test blood glucose before exercise, postpone exercise until after a snack if blood glucose is low and always keep glucose at hand.

• Autonomic neuropathy is common and can be associated with silent coronary heart disease, postural hypotension and a blunted heart rate response to exercise.

• Peripheral neuropathy is common and may lead to numbness, paraesthesiae, reduced balance, Charcot joints.

• Peripheral arterial disease: there may be intermittent claudication, leg ulcers, etc.

• Avoid high-impact exercise, as this may traumatise the feet (emphasise foot care, proper shoes and cotton socks).

• Hypoglycaemia may occur up to several hours after exercise.

• Exercise is contra-indicated if there is active retinal haemorrhage or recent retinal photocoagulation.

Type 2 diabetes¹³

NICE only gives generalised advice concerning the role of physical exercise in type 2 diabetes. Guidance can be found in the St Vincent Declaration.¹² Advise that physical exercise:

• Can benefit insulin sensitivity, BP and blood lipid control.

• Should be taken at least every 2-3 days for optimum effect.

• May increase the risk of acute and delayed hypoglycaemia.

Manage physical exercise using:

• Formal recording of levels of physical activity

• Identification of new exercise opportunities (see under 'Exercise', above) and encouragement to develop these.

• Appropriate self-monitoring, additional carbohydrate, and dose adjustment of glucose-lowering therapy for those using insulin secretagogues.

Warn about:

• Alcohol, which may exacerbate the risk of hypoglycaemia after exercise.

• The risks of foot damage from exercise (advise low-impact exercise).

• The need to consider coronary heart disease in those beginning new exercise programmes.

Type 1 diabetes¹⁴

Advise that physical activity can reduce enhanced arterial risk in the medium and longer term. Also give information on:¹⁰

• Appropriate intensity and frequency of physical activity.

• Role of self-monitoring of changed insulin and/or nutritional needs.

• Effect of activity on blood glucose levels (likely fall) when insulin levels are adequate.¹⁵

• Effect of exercise on blood glucose levels when hyperglycaemic and hypoinsulinaemic (risk of worsening of hyperglycaemia and ketonaemia).

• Appropriate adjustments of insulin dosage and/or nutritional intake for exercise and post-exercise periods, and the following 24 hours.

• Interactions of exercise and alcohol.

• Further contacts and sources of information.