Key learning points
- Dietary modification is the cornerstone of obesity management.
- Modest (10% weight loss) carries significant benefits to blood pressure (BP), glucose and lipid metabolism.
- This Factfile outlines methods of assessing dietary intake.
- It summarises modifications which can be applied to individuals that can lead to a weight loss of 0.5-1 kg per week.
The prevalence of obesity among adults in Britain has trebled in the last 20 years. In 2002, 22.1% of men and 22.8% of women were clinically obese with a body mass index (BMI) >30kg/m2. Obesity is associated with a reduction in life expectancy of approximately 9 years, mostly due to an increased risk of cardiovascular disease and certain cancers. It also increases the burden of ill-health, in particular Type 2 diabetes. Prevention of obesity is the key to reducing the long-term burden of obesity-related disease.
Average weight gain in the UK is less than 0.5 kg per year. A small increase in physical activity or a small decrease in energy intake will reverse this trend. However, more aggressive intervention is required for the one in five British adults who are already obese and at increased risk of ill health. Dietary changes remain the cornerstone of obesity treatment, together with increases in physical activity where possible.
The Diabetes Prevention Programme (DPP)1 provides good evidence of what can be achieved. Individuals in the intervention group demonstrated a sustained weight loss of 5.6 kg over four years with a 58% reduction in the incidence of Type 2 diabetes compared to the control group.
Treatment of obesity
Effective treatment of obesity must cut the risk of disease and improve overall health.The expected health benefits of modest weight loss are outlined in Table 1. Every kg of excess weight contains about 7,500 calories, so a daily energy deficit of around 1000 calories will lead to a weight loss of approximately 1 kg per week. This is a reasonable goal, but many patients (and their doctors), expect more rapid weight loss. This misunderstanding can lead to subsequent disappointment and poor long-term success rates.
Table 1: The health benefits of modest (10%) weight loss (SIGN, 1996)2 (The precise benefits will vary in individuals depending on initial body weight, current health and degree of weight loss).
20-25% reduction in premature death
30% reduction in the risk of dying from diabetes-related complications
40% reduction in the risk of dying from cancer
10mmHg decrease in systolic blood pressure
20mmHg decrease in diastolic blood pressure
50% fall in fasting blood glucose levels
10% fall in total cholesterol
15% fall in LDL cholesterol
8% increase in HDL cholesterol
Dietary treatment of obesity
Assessing dietary intake
Obtaining an understanding of what an individual eats is often difficult since obese people tend to under-report their food intake. This makes quantitative analysis complicated. However, qualitative information on dietary habits may reveal food choices and eating behaviours that can help to individualise dietary advice. Food diaries can be used to explore why, where and what people eat and help people focus on their eating habits. Points that are helpful in assessing dietary intake include the following.
- Meal patterns - regular meal eaters or snackers?
- Preferred foods - sweet or savoury?
- Food dislikes?
- 'Hard to resist' or 'trigger foods'?
- Typical portion size? - replica foods or food photographs can be useful
- Catering arrangements at work - packed lunches, canteen, pub etc?
- Cooking arrangements at home - who shops and cooks?
Basic treatment protocols for the management of obesity within the National Health Service (NHS) have been developed as part of the Scottish Guidelines (SIGN, 1996)2 and local protocols exist in many areas. However, standardised diet sheets are of little benefit as obese people require individualised dietary advice and long-term support. For some, successful support can be provided by a commercial weight loss group, or from family and friends.
Specific dietary issues
Dietary treatment should aim to alter the composition of the diet and tackle the broader aspects of eating behaviour. These include the following.
Reducing energy intake can be achieved by reducing habitual portion sizes. The following are appropriate portions:
- breakfast cereals - 3 tablespoons,
- rice - 2 heaped tablespoons
- 2 egg-sized potatoes.
Structured meals can help individuals to choose less energy-dense foods, rather than succumb to high fat/high sugar foods. (Skipping meals rarely helps to reduce overall energy intake).
Individuals should be given advice on snack choices. Fresh or dried fruit, raw vegetables, diet, yoghurts and low-sugar breakfast cereals with skimmed or semi-skimmed milk are appropriate.
Dietary treatment should aim to alter the composition of the diet.
Fat is the most energy dense macronutrient (9 kcal/g, compared with ~4kcal/g for carbohydrate or protein). Reducing dietary fat will reduce energy intake. People should be given advice on interpreting food labels, preferring those that contain <3g/100g fat and choosing low fat substitutes where possible. Also, to avoid adding fat during cooking and to consume only very small quantities of high fat foods.
Breads, pasta, potatoes and rice aid satiety and should provide the bulk of every meal. Unrefined, fibre-rich versions should be encouraged.
Protein is very satiating compared to carbohydrate and fat. Thus, modest increases in protein
intake may help appetite control (which may account for the popularity of the Atkins diet). Liberal quantities of lean protein sources, such as carcase meat, poultry (without skin), low-fat dairy products and pulses can facilitate adherence to a low-fat diet.
Fruit and vegetables
The energy density of most fruits and vegetables is low. They add bulk to a meal and help promote a feeling of fullness. They are rich in vitamins and phytochemicals which may have a protective effect on health.
High fat/high sugar foods
Foods such as cakes, biscuits, chocolate and sweets are energy-dense and should be avoided. However, eating these foods occasionally will not ruin weeks or months of dietary restraint.
Meal replacement plans
Meal replacements are commercially available, reduced energy products such as drinks or bars used to replace one or two meals in a day. When used in conjunction with healthy eating advice, they can aid compliance to a low calorie diet of between 800 and 1600 kcal per day.
A recent meta-analysis3 (Homesfield 2004) has shown that meal replacements can be an effective dietary strategy for short term weight loss. Further information on dietary management of obese individuals has been provided by Summerbell 19984.
1. Diabetes Prevention Programme Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New Engl J Medi 2002; 346: 393-403.
2. SIGN. Obesity in Scotland. Integrating prevention with weight management. Edinburgh: Royal College of Physicians, Edinburgh, 1996.
3. Heymsfield S B, van Mierol C A J, van der Knaap H C M, Heo M, Frier H I. Weight management using meal replacement strategy:meta and pooling analysis from six studies. International Journal of Obesity 2003; 27: 537-549.
4. Summerbell C D. Dietary treatment of obesity. In Kopelman P, Stock M J, eds. Clinical Obesity. London: Blackwell Science Ltd, 1998: 377-408.
Reproduced with kind permission from the British Heart Foundation - www.bhf.org.uk