Eating 500 Calories a day in excess of metabolic requirements will lead to a weekly weight gain of ½kg (1 lb).

Conversely, reducing intake by 500 Calories less than daily energy requirements will lead to ½kg (1 lb) weight loss a week.

As fat weight increases so does muscle weight (35% of excess body weight is muscle or cellular components of adipose which is metabolically active). As weight is lost, muscle weight can also decrease and there is a decrease in metabolic rate.

Hence the importance of aiming to do 30 minutes of moderately intensive exercise a day. This will increase energy expenditure and encourage muscle growth, which will increase the metabolic rate even when the person is not exercising.

Obesity can be caused by lifestyle such as excessive energy intake of palatable, high-energy foods combined with sedentary lifestyle. The time spent watching television has increased from 13 to 26 hours a week in the past 30 years.

An underactive thyroid can also reduce energy expenditure and hence increase body weight.

There are rare metabolic syndromes, such as Prader Willi, Lawrence Moon Biedl, Cushings, and tumour of hypothalamus, which result in obesity.

Genetic factors will influence the metabolic component of obesity; identical twins are twice as likely to have same weight as non-identical twins.

Psychological factors such as depression influence eating and exercise habits and may even affect fat distribution.

Apples and Pears

But obesity is not just about how much body fat there is. The fat distribution around the body also influences health.

Waist measurements are an indication of internal fat around the organs. Central fat distribution is associated with metabolic disorders such as NIDDM, hypertension, hyperlipidaemia and altered clotting factors. The Waist:Hip (W:H) ratio or the Waist Circumference on its own are used to indicate increased risk.

		There is an increased risk if the W:H ratio is > 1 in men and > 0.85 in women
		There is an increased risk if the Waist Circumference is > 37inches in men and > 32 inches in women.
		There is greatly increased risk if the Waist Circumference is > 40 inches in men and > 35 inches in women

How else do we measure obesity?

The standard method is by Body Mass Index (Weight (kg)/Height (m) x Height) ranges.

		Normal range: 18.5 - 24.9
		Grade I overweight: 25 - 29.9
		Grade II obese: 30 - 39.9
		Grade III obese: > 40

These ranges were developed from insurance-company data, which found that the risk of mortality was lowest at the BMI range of 18.5 - 24.9 and increased below and above this range.

However, there is evidence from American and Finnish studies that in older people the BMI range associated with minimum mortality is 21 - 27 for men and 23 - 27 for women.

		In older people, a greater BMI correlates better with a greater muscle mass whereas in younger people a greater BMI generally indicates greater amounts of fat (except in athletes).
		As muscle mass is an important predictor of survival in critical illness this may explain why greater BMIs are more desirable in older people
		In addition, a lower BMI in older people is a risk factor for osteoporosis and hip fractures. The National Institute of Health in the USA showed that in the > 50s, if the BMI was less than 29 there was no case for slimming unless there were specific additional conditions such as diabetes, hypertension, arthritis or sleep apnoea. To reflect this the National Research Council produces optimum BMI ranges which vary according to age[link to slide 4 in the Powerpoint presentation which Matt holds].

Obesity facts

		One in five adults are obese. This proportion has doubled in the past 20 years.
		10% of six year olds are obese.
		Obesity is increasing in UK faster than in other European countries.
		£500m is spent by NHS on obesity-related treatment.

What health problems does obesity cause?

		Being overweight significantly increases the risk of diabetes: 1/3 of obese middle-aged people will develop diabetes).
		Hypertension is more common in the obese.
		Incidence of cardiovascular disease doubles in the overweight and quadruples in the obese.
		The incidence of gallstones and some cancers (breast, endometrial, colorectal, prostate) also increases.
		Obesity exacerbates conditions such as heartburn, arthritis, breathlessness, and can complicate surgery.
		In Britain, there is a social stigma associated with obesity and this can affect mental health.
		18 million sick days a year are attributed to the sufferers being overweight or obese.
		30,000 deaths a year (6% of all deaths) are estimated to be from obesity-related causes.
		Deaths linked to obesity shorten life by nine years on average; in 1998, 9000 deaths before retirement age were associated with obesity

What is the Government's response to the problem of obesity?

The NHS National Service Framework (NSF) for CHD includes action to address obesity, diet and physical activity:
www.publications.parliament.uk/pa/cm200102/
cmselect/cmpubacc/421/42103.htm

(Note that the above address must be entered all on one line if you are typing it in)

The National Audit Office report (http://www.nao.gov.uk ) Tackling Obesity in England (February 2001) was discussed at a conference Joining Forces to tackle obesity in 2002.

This report found that GPs are unclear about how to go about treating the overweight and obese. Although 40% of GPs use drug therapy they were uncertain about its effectiveness.

The consensus is that no single agency can tackle the problem of obesity. Integrated action is needed by those responsible for healthcare, education, transport, sport and recreation, and the production, retailing, labelling and marketing of food.

Local Health Authority improvement programmes are charged with setting timetables and targets for action to address the needs of obese people.

GP practices have been advised to employ more health professionals to identify patients with weight problems and provide advice and support on weight control.

The evidence for effectiveness of obesity treatment has been reviewed by some notable organisations.

		The Royal College of Physicians 1998 Clinical management of overweight and obese patients.
		Scottish Intercollegiate Guidelines Network (SIGN) 1996 Management of obese patients in Scotland - how to audit interventions in obesity
		Effective health care bulletins Obesity 1997: http://www.york.ac.uk
		British Dietetic Association Journal of Human Nutrition and Dietetics and the specialist group, Dietitians in Obesity Management: www.bda.uk.com
		http://www.aso.org.uk