Individual and Population Examples

Consider the following two examples of obesity. The first is Penny who is 45 years old and, apart from a few years around the time of her wedding, has always been quite chubby. Over the last 15 years she has gained a lot more weight and now has a body mass index (BMI) of 34 kg/m2. Her husband, on the other hand, has a BMI of ~25 kg/m2, and this has virtually not changed since he left school. The second example is England where the prevalence of obesity (BMI >30 kg/m2) in 1996 was 17% (3) having increased from 7% in 1980 (4). England's neighbor just across the English Channel is the Netherlands, where the prevalence of obesity in 1995 was only 8%, up from about 6% in 1981 (5). These two examples illustrate the different perspectives needed for dealing with individuals or populations. The etiologies and management strategies will be quite different for Penny's obesity compared to England's obesity (Table 1).

The etiology of Penny's obesity will tend to be ascribed to genetic, metabolic, hormonal, and behavioral factors, whereas for England it will tend to be environmental, sociocultural, and behavioral. For example, the transport environment in England will stand out as ''obesogenic'' (obesity promoting) because of its automobile dependence compared to the relatively ''leptogenic'' (leanness promoting; leptos is Greek for thin) transport environment in the Netherlands with its strong emphasis on bicycle and public transport travel.

The management strategies for obesity at the individual and population levels are also quite different (Table 1). The volume of studies and information about weight loss is huge compared to the amount available on population-based prevention. For example, the recent 150-page Report of the British Nutrition Foundation s, Task Force on Obesity dedicated 51 pages to treatment of individuals and only one page to population prevention strategies (6). This is, in part, because the driving g forces for research and action are quite different. For individual treatment, the forces are powerful and immediate; they include the clinical imperative to help people g with obesity, the pressure from individuals to lose

Table 1 Differences Between the Individual-Based and Population-Based Approaches to Obesity

Individual-based approach

Population-based approach

Key measures Key etiology question

Main etiological mechanisms Key management question

Main management actions

Volume of information on etiology and management Driving forces for research and action Potential for long-term benefit to individuals Potential for long-term benefit to populations

Body weight, waist, BMI

Why is this particular person obese (or gaining weight)?

Genetic, metabolic, hormonal, behavioral

What are the best long-term strategies for reducing the person's body fat?

Patient education, behavioral modification, drugs, surgery

Vast

Immediate and powerful

Modest

Modest

Prevalence of overweight and obesity, mean BMI and waist Why does this particular population have a high (or rising) prevalence of obesity?

Environmental, cultural, behavioral

What are the best long-term strategies for reducing the population's mean BMI?

Public education, improving food and physical activity environments, policy, planning Minimal

Distant and weak

Modest

Significant weight, and the huge potential profits for pharmaceutical companies from weight loss medications. Contrast this with the relatively weak and distant driving forces for population-based prevention research and action. These are funded largely from government sources, and the lack of political will due to a short-term political focus and limited public pressure for change remain major obstacles. As discussed later, the driving forces for the obesity epidemic are linked to much broader sectors such as transport, the food industry, education, urban planning, building design, and local government, and this adds to the sense of impotence among health authorities about obesity prevention.

As a general rule, individual-directed interventions bring about significant benefits to the individuals but have little impact on the population rates of disease or condition in question and vice versa for population-based interventions, which generally bring little benefit to each individual but have the potential to influence the prevalence or incidence of the condition (7). With obesity, this discrepancy is even more exaggerated (compared to, say, hypertension or hypercholesterolemia) because available individual interventions, apart from surgery, have modest long-term effects for the individuals under treatment (8,9). The efforts on population-based interventions related to obesity are much needed but are still in their infancy (1,10,11).

The potential for populationwide effects is particularly strong for high volume foods or physical activities. For example, a recent survey of fast food outlets in New Zealand showed that the mean fat content of the french fries was 11.5% by weight (12). There was an enormous range across the country, from 5% to 20%, and in many instances the deep-frying practices were very poor. It should be possible to reduce the mean fat content to 9% through a national training program for fast-food outlet operators, which is now under way. If this could be achieved, the consumption of french fries is such that the reduction in fat intake would be ~1/2 kg per capita per year. This is not insubstantial compared to the current increase in weight of the New Zealand adult population of ~1/3 kg per person per year (13).

C Linking the Individual and Population Approaches

There are synergies to be achieved by bringing the individual and population approaches together. This can be seen most clearly at the general-practice/primary-care level. For example, a general practitioner will have a greater chance of helping Penny to lose weight and keep it off if her obesogenic environments are acknowledged and, where possible, acted upon. Part of Penny's weight gain response to her obesogenic environment may be genetically determined, and recognition of this also helps to remove moral judgments about her obesity and places her individual behaviors into a wider context. The more limited behavior-based perspective can too easily be judged (by her and others) in '' sloth-and-gluttony'' terms. Penny may even be able to take action to make her own environments more leptogenic such as changing the types of food available at home or on offer at the work cafeteria. She may even decide to remove the batteries from the TV remote control and advocate for bike stands and showers at work.

On the flip side, it makes sense to use the high contact that primary health care has with the public on a regular basis to further the population health goals for obesity. Educating and up-skilling large numbers of patients increases the dissemination of knowledge through the community and promotes advocacy to make healthy choices easier.

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