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Team Leader: Dr Ted Coles

Literature searches completed on 27.7.99

Chapter 3: Food and Health (including Overweight and Obesity)

This bulletin is a supplement to, not a substitute for, professional skills and experience. Users are advised to consult the supporting evidence for a consideration of all the implications of a recommendation.
The relationship between food and health is significant. Diet plays an important part in both promoting good health and well-being, and in the development of a number of health problems including obesity, coronary heart disease and cancer. This chapter considers interventions to improve the diet of the general population, and nutritional interventions for overweight and obesity.
Caveat: In common with other topics in this bulletin, there are few well-designed experimental studies which evaluate the effectiveness of health promotion interventions to promote healthy eating. An appraisal of those that do exist is further hampered by the wide ranging outcomes identified by different interventions i.e. changes in knowledge, changes in dietary intake, food choices and biochemical indicators of nutrient status. This chapter draws largely from the systematic reviews commissioned by the Health Education Authority into the effectiveness of interventions to promote healthy eating in different population groups. Readers are encouraged to seek out these reviews. The majority of studies cited in these reviews are from the US, many related to the substantial Women’s Infants and Child (WIC) Headstart and other nationally funded programmes which included an educational component in conjunction with food vouchers/supplies. In none of the studies is cost-effectiveness data presented; where positive effects are shown, sufficient information is not provided to make judgements about whether the size of the effect is sufficient to be significant in relation to the cost of the intervention.
The Statements The Evidence
3.1. Diet and Health

3.1a. A varied diet that meets the dietary reference values for energy and nutrients will be beneficial to healthi.
(Health gain notation – 1 "beneficial")

i. Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report on Health and Social Subjects No. 41. London: The Stationery Office, 1991
(Type V evidence – expert opinion)

3.1b. It is estimated that, on average, a third of cancers could be prevented by changes in dieti.
(Health gain notation – 1 "beneficial")
A diet which is high in fibre (fruit & vegetables) and whole grain cereal and low in fat has the potential to prevent a number of cancers, including colorectal and breast cancer.
(Health gain notation – 2 "likely to be beneficial")

i. Department of Health. Committee on Medical Aspects of Food and Nutrition Policy. Working Group on Diet and Cancer. Nutritional Aspects of the Development of Cancer. Report on the Health and Social Subjects No. 48. London: The Stationery Office, 1998
(Type V evidence – expert opinion based on observational studies)
3.1c. A diet high in fat (particularly saturated fat) and high in salt is associated with an increased risk of coronary heart diseasei.
(Health gain notation – 6 "likely to be harmful")

 

i. Department of Health. Diet and Cardiovascular Disease. London: The Stationery Office, 1994
(Type V evidence – expert opinion based on observational and interventional studies)

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3.1d. A diet rich in fruit and vegetables is associated with a decreased risk of coronary heart diseasei.
(Health gain notation – 2 "likely to be beneficial")
i. Department of Health. Diet and Cardiovascular Disease. London: The Stationery Office, 1994
(Type V evidence – expert opinion based on observational and interventional studies)
ii. National Heart Forum. Preventing Coronary Heart Disease – The Role of Antioxidants, Vegetables and Fruit. London: The Stationery Office, 1997
(Type V evidence – expert opinion based on observational and interventional studies)
3.1e. A reduction in the consumption of non-milk extrinsic sugars is associated with reduced levels of tooth decayi.
(Health gain notation – 1 "beneficial")
i. Department of Health. Dietary Sugars and Human Disease. London: The Stationery Office, 1989
(Type V evidence – expert opinion based on observational and interventional studies)
3.1f. In Wales only 23.9% of adults eat green vegetables or salad six or seven days a weeki. i. The National Assembly for Wales. Welsh Health Survey 1998. Results of the Second Welsh Health Survey. Cardiff: Government Statistical Service, 1999
http://www/wales.gov.uk/polinifo/health/keypubs/
pdf/acro.htm [accessed 8.12.00]
(Type IV evidence – survey of 50,023 adults in Wales, representing one in every 45 adults. Adjusted overall response rate, 61%)
3.1g. People who are obese (Body Mass Index, BMI>30) or overweight (BMI>25) have a higher risk of disease including coronary heart disease, diabetes, hypercholesterolaemia, hypertension, bone and joint disorders. The risk of disease increases with increasing BMIi.ii.iii.
Men and women with a waist circumference greater than 94cm and 80cm respectively are at increased risk and men and women with a waist circumference greater than 102cm and 88cm respectively are at substantial risk.iv
i. The prevention and treatment of obesity. Effective Health Care 1997; 3(2) http://www.york.ac.uk/inst/crd/ehc32.htm [accessed 10.3.00]
(Type IV evidence – systematic review citing 2 observational studies and 2 reviews of observational studies)

ii . Department of Health. Nutrition and Physical Activity Task Force. Obesity: Reversing the Increasing Problem of Obesity in England. London: The Stationery Office, 1995
(Type V evidence – expert opinion)
iii. Health Evidence Bulletins – Wales. Cardiovascular Diseases. Cardiff: Welsh Office, 1998 http://hebw.cardiff.ac.uk/cardio/index.html [accessed 10.3.00]
(Type IV evidence – prospective cohort studies)

iv. Scottish Intercollegiate Guidelines Network (SIGN) Obesity in Scotland. Integrating Prevention with Weight Management. SIGN Guidelines No 8. Pilot Edition, November 1996. http://www.sign.ac.uk [accessed 10.3.00]
(Type IV evidence – systematic review citing 2 observational studies)

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3.1h. Intra-abdominal obesity assessed by GHR (waist circumference divided by height) or WHR (waist hip ratio), carries a greater risk of cardiovascular disease, hypertension and non-insulin dependent diabetes than other types of obesity (eg hips, thighs, peripheral areas)i,ii,iii. i. The prevention and treatment of obesity. Effective Health Care 1997; 3(2) http://www.york.ac.uk/inst/crd/ehc32.htm [accessed 10.3.00]
(Type IV evidence – systematic review citing Colhoun H, Prescott-Clark P, eds. Health Survey for England, 1994. A survey carried out for the Department of Health Vol. 1. London: The Stationery Office, 1996)

ii. Department of Health. Nutrition and Physical Activity Task Force. Obesity: Reversing the Increasing Problem of Obesity in England. London: The Stationery Office, 1995
(Type V evidence – expert opinion)
iii. Health Evidence Bulletins – Wales. Cardiovascular Diseases. Cardiff: Welsh Office, 1998 http://hebw.cardiff.ac.uk/cardio/index.html [accessed 10.3.00]
(Type IV evidence – prospective cohort studies)
3.1i. In Wales 55.2% of adults are overweight or obese with a Body Mass Index (BMI) of 25 or greateri. i. The National Assembly for Wales. Welsh Health Survey 1998. Results of the Second Welsh Health Survey. Cardiff: Government Statistical Service, 1999
http://www.wales.gov.uk/polinifo/health/keypubs/
pdf/acro.htm [accessed 8.12.00]
(Type IV evidence – survey of 50,023 adults in Wales, representing one in every 45 adults. Adjusted overall response rate, 61%)
3.2. General Health Education
3.2a. Healthy eating interventions targeted at a range of population groups in a range of settings are effective in achieving dietary change. The characteristics associated with effective interventions werei:
  • A focus on diet or diet and exercise only.
  • A behaviourally-based theoretical model.
  • A degree of personalisation of the intervention, usually by a health professional.
  • The provision of feedback.
  • Active involvement of influential people eg family, community leaders.
  • Changes in local environment and policy for long-term change.

(Health gain notation 2 – "likely to be beneficial")

i. Roe L, Hunt P, Bradshaw H and Rayner M. Health Promotion Interventions to Promote Healthy Eating in the General Population: A Review. Health Promotion Effectiveness Reviews 6. London: Health Education Authority, 1997. http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview6.html
[accessed 10.3.00]
(Type I evidence – systematic review of 76 intervention studies)

 

 

 

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3.2b. Traditional group based teaching has a positive impact on knowledge and/or self reported dietary behaviour in a number of population groups including the under 5’s, pregnant women and elderly people in community settingsi,ii,iii.
(Health gain notation 2 – "likely to be beneficial")
i. Van Teijingen E, Wilson B, Barry N, Ralph A, McNeill G, Graham W and Campbell. Effectiveness of Interventions to Promote Healthy Eating in Pregnant Women and Women of Childbearing Age: A Review. Health Promotion Effectiveness Reviews 11. London. Health Education Authority 1998. http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview11.html
[accessed 10.3.00]
(Type I evidence – systematic review of 4 randomised controlled trials)

ii. Tedstone A, Aviles M, Shetty P and Daniels L. Effectiveness of Interventions to Promote Healthy Eating in Pre-school Children Aged 1 to 5 Years: A Review. Health Promotion Effectiveness Reviews 10. London. Health Education Authority 1998. http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview10.html
[accessed 10.3.00]
(Type I evidence – systematic review of 14 intervention studies of variable quality)

iii. Fletcher A and Rake C. Effectiveness in Interventions to Promote Healthy Eating in Elderly People Living in the Community: A Review. Health Promotion Effectiveness Reviews 8. London. Health Education Authority. 1998. http://www.hda-online.org.uk/html/
research/effectivenessreviews/ereview8.html
[accessed 10.3.00]
Type I evidence – systematic review of 8 intervention studies of variable quality)
3.2c. Interventions that target the mothers of children under 5 years of age, using educational interventions, have positive effects on the mothers’ knowledge, behaviour and the children’s dieti.
(Health gain notation 2 – "likely to be beneficial")
Caveat: Includes US studies as part of WIC and Headstart programmes that include provision of food vouchers, effect of individual components not measured.
i. Tedstone A, Aviles M, Shetty P and Daniels L. Effectiveness of Interventions to Promote Healthy Eating in Pre-school Children Aged 1 to 5 Years: A Review. Health promotion effectiveness reviews 10. London: Health Education Authority, 1998. http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview10.html
[accessed 10.3.00]
(Type III evidence – systematic review citing 3 non-randomised intervention studies)

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3.3. Healthcare Based Interventions

3.3a. Interventions to promote breast feeding are successful in increasing initiation and duration of breast feeding. The characteristics of effective interventions are that they span the ante and post natal periods, are specific to breast-feeding and include multiple contacts with either a health professional or lay counsellori.
(Health gain notation 1 – "beneficial")
i . Tedstone A, Dunce N, Aviles M, Shetty P, Daniels L. Effectiveness of Interventions to Promote Healthy Feeding in Infants Under One Year of Age: A Review. Health promotion effectiveness reviews 9. London: Health Education Authority, 1998. http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview9.html
[accessed 10.3.00]
(Type I evidence – systematic review of 20 intervention studies of variable quality)
3.3b. Interventions through primary healthcare, using nurse led intervention via health check or computer tailored mailed intervention, showed a reduction of blood cholesterol levels (2-3%) or dietary fat intake of (1.4-4%) of energy sustained for four months to three years after the interventioni.
(Health gain notation 2 – "likely to be beneficial")
i . Roe L, Hunt P, Bradshaw H and Rayner M. Health Promotion Interventions to Promote Healthy Eating in the General Population: A Review. Health promotion effectiveness reviews 6. London: Health Education Authority, 1997 http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview6.html
  [accessed 10.3.00]
(Type I evidence – systematic review citing 7 randomised controlled trials, 4 of good quality)
3.3c. Interventions delivered through a health check, including a nutrition component and using a feedback/goal setting approach can lead to self reported dietary changes in elderly peoplei.
(Health gain notation 2 – "likely to be beneficial")
Caveat: These studies are US based and delivered through health insurance schemes.
i. Fletcher A and Rake C. Effectiveness in Interventions to Promote Healthy Eating in Elderly People Living in the Community: A Review. Health Promotion Effectiveness Reviews 8. London. Health Education Authority. 1998. http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview8.html
[accessed 10.3.00]
(Type I evidence – systematic review citing 4 randomised controlled trials and 1 cohort study, of variable quality)

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3.4. School-Based Interventions

3.4a. School-based interventions were assessed as part of a systematic review i. Twenty-one studies were included of which seven were judged to be of good quality. The range of interventions used centred on traditional classroom based education supplemented by one or more other components e.g.parental/home involvement, modification of school meal system, health screening including cholesterol testing. Four of the seven good quality studies and 10 of the total showed a positive effect on either dietary intake or blood cholesterol.
A number of reviews of school-based nutrition education programmes have drawn similar conclusions on the characteristics of successful programmes i, ii, iii, . These include the following:
  • Effective programmes are behaviourally focused.
  • Interventions are more effective when derived from appropriate theory and research.
  • The greater the level of intensity of the programme the greater the effect.
  • Family involvement is beneficial for younger children.
  • Self evaluation/assessment and feedback is an effective component of programmes for older children.
  • Interventions in the wider school environment should form a component of the programme.
  • Interventions in the wider community can enhance school programmes.

(Health gain notation – 2 "likely to be beneficial")

i. Roe L, Hunt P, Bradshaw H and Rayner M. Health Promotion Interventions to Promote Healthy Eating in the General Population: A Review. Health promotion effectiveness reviews 6. London: Health Education Authority, 1997. http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview6.html
[accessed 10.3.00]
(Type I evidence – systematic review of 21 intervention studies of variable quality)

ii. Contento I, Balch GI, Maloney SK et al. The effectiveness of nutrition education and implication for nutrition education policy, programs and research: A review of research. Journal of Nutrition Education 1995; 27: 277-419.
(Type I evidence – systematic review of 43 intervention studies)
iii. Lytle L and Achterberg C. Changing the diet of America’s children: what works and why. Journal of Nutrition Education 1995; 27: 250–260
(Type I evidence – systematic review of 43 intervention studies)

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3.5. Workplace Interventions

3.5a. Interventions set in the Workplace using diet only and multi-factoral approaches have a positive effect on reducing dietary fat intake (1%–16% of energy) and blood cholesterol levels (2.5%–10%)i.
(Health gain notation 2 – "likely to be beneficial")
i. Roe L, Hunt P, Bradshaw H and Rayner M. Health Promotion Interventions to Promote Healthy Eating in the General Population: A Review. Health Promotion Effectiveness Reviews 6. London: Health Education Authority, 1997 http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview6.html
[accessed 10.3.00]
(Type I evidence – systematic review citing 9 randomised controlled trials, 4 of which were assessed as good quality)
3.6. Community-Based Interventions
3.6a. There are a number of community-based interventions that appear promising, for example food co-operatives, bulk buy schemes, cooking programmes and community cafes. At present there is little good quality evaluation of these interventions. There is a need for further research in this area.  

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3.7. Supportive Environments

3.7a. The use of supermarket based interventions e.g. provision of shelf signs, point of sale information appears promising in positively effecting food purchases in the long-term (1% – 2% increase in sales) but require further explorationi.
(Health gain notation 2 – "likely to be beneficial")
i. Roe L, Hunt P, Bradshaw H and Rayner M. Health Promotion Interventions to Promote Healthy Eating in the General Population: A Review. Health Promotion Effectiveness Reviews 6. London: Health Education Authority, 1997 http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview6.html
[accessed 10.3.00]
(Type I evidence – systematic review citing 8 intervention studies of which 4, 1 randomised controlled trial and 3 cohort studies, were assessed as good quality)
3.7b. Interventions in catering, through passive (modification of recipes and choices offered) and active (promotion of particular choices) methods, have a positive effect on nutrient intake/food choices made at the catering outlet for the intervention period. The effect on the overall diet is unknowni.
(Health gain notation 2 – "likely to be beneficial")
i. Roe L, Hunt P, Bradshaw H and Rayner M. Health Promotion Interventions to Promote Healthy Eating in the General Population: A Review. Health promotion effectiveness reviews 6. London: Health Education Authority, 1997 http://www.hda-online.org.uk/html/research/
effectivenessreviews/ereview6.html
[accessed 10.3.00]
(Type I evidence – systematic review of 15 intervention studies)
3.8. Prevention of Obesity
3.8a. Family therapy (defined as a model of treatment involving the family) may be more effective than conventional diet/exercise treatments or no intervention, at preventing progression of obesity in children (10-11 years of age). (Increase in BMI in intervention group 5.1% vs 12% in control group, p=0.02; children with severe obesity in intervention group 5% vs 29% in control group, p=0.02)i.
(Health Gain Notation 2 – "likely to be beneficial")
i. The prevention and treatment of obesity. Effective Health Care 1997; 3(2) http://www.york.ac.uk/inst/crd/ehc32.htm
[accessed 10.3.00]
(Type I evidence – systematic review citing one randomised controlled trial: Flodmark CE, Ohlsson T, Ryden O, Sveger T. Prevention of progression to severe obesity in a group of obese school children treated with family therapy. Pediatrics 1993; 91: 880–884)

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3.9. Treatment of Obesity

3.9a. Interventions to reduce sedentary behaviour in children in combination with moderate changes in diet and lifestyle which avoid restrictive diets and exercise programmes are effective at reducing obesity in childreni.
(Health gain notation 2 – "likely to be beneficial")
i. The prevention and treatment of obesity. Effective Health Care 1997; 3(2) http://www.york.ac.uk/inst/crd/ehc32.htm   [accessed 10.3.00]
(Type I evidence – systematic review of 11 randomised controlled trials; conclusions drawn from 2 good quality trials)
3.9b. Interventions to reduce obesity in adults which include more than one approach in combination (behavioural therapy, exercise, diet modification) are more likely to be effective than single interventions (minimum 1 year treatment and follow up)i.
(Health gain notation 2 – "likely to be beneficial")

Clinical guidelines for the prevention, assessment and management of obesity are available and should form the  basis of  weight   management  interventionsii, iii.
(Health gain notation 2 – "likely to be beneficial")
i. The prevention and treatment of obesity. Effective Health Care 1997; 3(2) http://www.york.ac.uk/inst/crd/ehc32.htm [accessed 10.3.00]
(Type I evidence – systematic review citing at least 8 randomised controlled trials in addition to other intervention studies)

ii. Scottish Intercollegiate Guidelines Network (SIGN) Obesity in Scotland. Integrating Prevention with Weight Management. SIGN Guidelines No 8. Pilot Edition, November 1996 http://www.sign.ac.uk [accessed 10.3.00]
(Type I evidence – guideline based on a systematic review)

iii. National Heart, Lung and Blood Institute. Clinical Guidelines on the Identification, Evaluation and Treatment of Overweight and Obesity in Adults. Bethesda: Maryland, 1998 http://www.nhlbi.nih.gov/nhlbi/cardio/obes/
prof/guidelns/ob-exsum.htm
[accessed 10.3.00]
(Type I evidence – guideline based on a systematic review including 394 randomised controlled trials)
3.9c. Very Low Calorie Diets (800 kcal/d; 3350kj/d or less) can be effective at promoting significant short-term weight loss in obese patients. However, long-term maintenance of weight loss suggests no benefit over other dietary treatments. Incorporation of behavioural modification and exercise in treatment programmes may improve maintenancei.
(Health gain notation 3 – "trade off between beneficial and adverse effects")
i National Task Force on the prevention and treatment of obesity. Very low calorie diets. Journal of the American Medical Association 1993; 270: 967–974.
(Type III evidence – systematic review of controlled clinical trials and other studies)

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3.9d. The role of health professionals in the management of obesity and the most appropriate way of developing knowledge and skills in this area and the motivation to address the issue is unknown i. The most appropriate service model for the management of obesity is unknown i ii.
(Health gain notation 4 – "unknown")
Additional research in this field is required
i. Harvey EL, Glenny A, Kirk SLF, Summerbell CD. Improving health professionals’ management and the organisation of care for overweight and obese people. Cochrane Database of Systematic Reviews. Cochrane Library 1999 Issue 2 http://www.update-software.com/ccweb/cochrane/
revabstr/ab000984.htm
[accessed 10.3.00]
(Type I evidence – systematic review of 12 intervention studies, 3392 patients in all, including 3 randomised controlled trials; also published as Harvey EL, Glenny AM, Kirk SFL, Summerbell CD. A systematic review of interventions to improve health professionals’ management of obesity. International Journal of Obesity 1999; 23: 1213-1222)

ii. Hughes J, Martin S. The Department of Health’s project to evaluate weight management services. Journal of Human Nutrition and Dietetics 1999; 12 (Suppl.1): 1–8.
(Type IV evidence - descriptive study of the findings of the evaluation of 13 weight management services in England. Information on the nature of the individual services or the evaluation methods used was not provided)

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3.10. Weight Maintenance

3.10a. Weight loss programmes should include mechanisms for longer-term follow-up and maintenance to minimise regaini.
(Health gain notation 2 – "likely to be beneficial")
i. The prevention and treatment of obesity. Effective Health Care 1997; 3(2) http://www.york.ac.uk/inst/crd/ehc32.htm   [accessed 10.3.00]
(Type I evidence – systematic review of 21 randomised controlled trials)
3.10b. Combined treatment and maintenance programmes including behavioural therapy, relapse prevention and telephone or mail contact are effective at promoting weight maintenancei.
(Health gain notation 1 – "beneficial")
i. The prevention and treatment of obesity. Effective Health Care 1997; 3(2) http://www.york.ac.uk/inst/crd/ehc32.htm   [accessed 10.3.00]
(Type I evidence – systematic review of 11 randomised controlled trials)
3.10c. The evidence regarding the negative effects of weight cycling (repeated loss and gain or weight) is not sufficient to override the potential benefits to obese patients of weight loss. However, consideration should be given to weight maintenance as a component of weight loss programmesi.
(Health gain notation 2 – "likely to be beneficial")
i . National Task Force on the prevention and treatment of obesity. Weight cycling. Journal of the American Medical Association 1994; 272: 1196–1202
(Type III evidence – systematic review of 28 (uncontrolled) interventional and observational studies)

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Health Evidence Bulletins: Wales, Duthie Library, UWCM, Cardiff CF14 4XN. e-mail: weightmanal@cardiff.ac.uk