1. Obesity, diet and physical activity P.Myles Puja.myles@nottingham.ac.uk

2. Learning outcomes You should be able to: describe how obesity, diet and physical activity impact on population health Recognise the various factors that influence individual behaviour discuss various public health approaches to tackling obesity

3. Lecture outline What is obesity? Who is at risk? Is obesity a population health issue? What influences individual behaviour? Public health approaches to tackling obesity

4. What is obesity?

5. Disease, risk factor or lifestyle choice? “ A disease in which excess body fat has accumulated to such an extent that health may be adversely affected” -(WHO)

6. Measuring obesity-1 Body mass index (BMI): measures relative weight for height Calculated by dividing weight in kilograms by height in metres squared (kg/m 2 ) Limitations: –Does not take into account factors like age and gender (particularly an issue in children) –Does not distinguish between weight associated with muscle mass and fat

7. Measuring obesity-2 WHO classification of obesity WHO classificationBMI (kg/m 2 ) Underweight<18.5 Normal weight (healthy weight)18.5-24.9 Pre-obese (overweight)25-29.9 Obese class 1 (moderately obese)30-34.9 Obese class 2 (severely obese)35-39.9 Obese class 3 (morbidly obese)40 and above

8. Measuring obesity-3 Waist-hip ratio Rationale: overweight people with central fat distribution are at greater risk of developing heart disease and diabetes Apple-shaped ( higher/lower WHR?) versus pear-shaped ( higher/lower WHR?)

9. Who is at risk?

10. Causes of obesity Energy intake> energy expenditure Behavioural factors: physical activity, diet, eating patterns Genetic factors Medical factors: endocrine disorders (hypothyroidism), medication (corticosteroids) Others: ageing, smoking, pregnancy

11. Susceptible groups Children where one of both parents are overweight or obese Socially deprived groups or those on low income Ethnic minority groups Those with low levels of education People with learning difficulties

12. Is Obesity a Public Health problem?

13. Relative risk of health problems associated with obesity Greatly increased (RR >3): NIDDM, gall bladder disease, dyslipidaemia, insulin resistance, breathlessness, sleep apnoea Moderately increased (RR 2-3): CHD, hypertension, osteoarthritis (knees), hyperuricaemia and gout Slightly increased (RR 1-2): Cancers (breast, endometrial, colon), polycystic ovary syndrome, impaired fertility, back pain

14. Nutrition transition Obesity rates associated with economic development of a country In poor societies, the more affluent have a higher prevalence of obesity As societies develop, more affluent groups have lower obesity

15. We live in increasingly obesogenic environments… “…resulting from a multitude of genetic, biological, psychological, sociocultural, and environmental factors that affect both sides of the energy balance equation…” -(US Food and Nutrition Board, 2005)

16. Obesogenic environments Energy intake (dietary behaviours and patterns) affordability of food eating out convenience foods food deserts Energy expenditure (physical activity) Cars desk jobs TV internet

17. Passive obesity “The epidemic of ‘passive obesity’ is a normal response of our innate biology when confronted with modern living in ‘obesogenic’ environments so everyone, except the genetically very resistant, are guaranteed to put on weight except in unusual social circumstances” -Foresight report (2007). Tackling obesity: future choices

18. Small errors in energy balance and biological maintenance An average discrepancy of 10-20 kcal/day between energy intake and energy expenditure = 0.5-1kg of weight gain/year in early adult life Biological maintenance of obesity: as weight gain occurs, ‘resetting’ of neuroregulatory system so the extra weight is the new ‘normal’ default weight setting

19. Is it all about individual behaviours? Not all individuals are obese even if they live in an obesogenic environment Can energy imbalance be rectified by more physical activity and healthy diets? Is obesity a manifestation of poor will power? Should the individual be responsible entirely?

20. Factors influencing behaviour Health Belief Model (Rosenstock et al) A person’s behaviour is a determinant of their health beliefs: threat perception and behavioural evaluation (benefits vs. costs of action) Cues to action e.g. mass media campaign, legislation Self-efficacy

21. Achieving lifestyle change: The Three Es model

22. Public health approaches to tackling obesity

23. Changing Physical Environments Physical changes in design of environment for physical activity involving: –play areas –safe pedestrian and cycling friendly streets –Food availability in shops (especially in deprived areas)

24. Economic measures Refers to costs associated with food and physical activity Could include incentives or taxes at either local or national level: –Subsidising healthy food –Penalties for providing unsafe or unhealthy food –Finance new public transport systems

25. Political measures Refers to rules associated with physical activity and diet including laws, regulations, policies and institutional rules: –Food labelling with appropriate understandable health-related information –Regulation of food advertising aimed at children –Town planning policies which prioritise active transport (walking and cycling)

26. Changing Sociocultural Environments Refers to a community’s/society’s attitudes, beliefs and values towards diet and physical activity Measures could include: –Promoting physical activity in the workplace –‘Health-promoting schools’ with an ethos of nutritious healthy school dinners –Using role models (like celebrities) to influence healthy diet (Jamie Oliver) and physical activity (Dame Kelly Holmes)

27. Summary What is obesity? Who is at risk? Is obesity a population health issue? What influences individual behaviour? Public health approaches to tackling obesity

28. Key Reading Chapter 5:Obesity In Ewles (2005). Key topics in Public Health: Essential briefings on prevention and health promotion. Elsevier Chapter 9.5: Obesity In Detels et al (2009). Oxford Textbook of Public Health. Oxford University Press