Obesity and overweight

Obesity and overweight Introduction. One of the most common problems related to lifestyle today is being overweight.

Severe overweight or obesity is a key risk factor in the development of many chronic diseases such as heart and respiratory diseases, non-insulin-dependent diabetes mellitus or Type 2 diabetes, hypertension and some cancers, as well as early death. New scientific studies and data from life insurance companies have shown that the health risks of excessive body fat are associated with relatively small increases in body weight, not just with marked obesity.

Obesity and overweight are serious problems that pose a huge and growing financial burden on national resources. However, the conditions are largely preventable through sensible lifestyle changes. What is obesity and overweight? Obesity is often defined simply as a condition of abnormal or excessive fat accumulation in the fat tissues (adipose tissue) of the body leading to health hazards. The underlying cause is a positive energy balance leading to weight gain i.e. when the calories consumed exceed the calories expended. In order to help people determine what their healthy weight is, a simple measure of the relationship between weight and height called the Body Mass Index (BMI) is used. BMI is a useful tool that is commonly used by doctors and other health professionals to determine the prevalence of underweight, overweight and obesity in adults. It is defined as the weight in kilograms divided by the square of the height in metres (kg/m2). For example, an adult who weighs 70 kg and whose height is 1.75 m will have a BMI of 22.9 kg/m2. Overweight and obesity are defined as BMI values exceeding 25 and 30, respectively. Typically, a BMI of 18.5 to 25 is considered 'healthy', but an individual with a BMI of 25–29 is considered "at increased risk" of developing associated diseases and one with a BMI of 30 or more is considered at "moderate to high risk" [1].

BODY MASS INDEX <18.5 Underweight 18.5 - 25 Healthy weight 25 - 30 Overweight > 30 Obese

Fat distribution: apples and pears BMI still does not give us information about the total fat or how the fat is distributed in our body, which is important as abdominal excess of fat can have consequences in terms of health problems. A way to measure fat distribution is the circumference of the waist [2]. Waist circumference is unrelated to height and provides a simple and practical method of identifying overweight people who are at increased risk of obesity-related conditions. If waist circumference is greater than 94-102 cm for men and 80-88 cm for women, it means they have excess abdominal fat, which puts them at greater risk of health problems, even if their BMI is about right [3, 4].

The waist circumference measurement divides people into two categories: individuals with an android fat distribution (often called "apple" shape), meaning that most of their body fat is intra-abdominal and distributed around their stomach and chest and puts them at a greater risk of developing obesity-related diseases. Individuals with a gynoid fat distribution (often called "pear" shape), meaning that most of their body fat is distributed around their hips, thighs and bottom are at greater risk of mechanical problems. Obese men are more likely to be "apples "while women are more likely to be "pears" [5]. The dynamics of energy balance: the bottom line? The fundamental principle of energy balance is:

Changes in energy (fat) stores = energy (calorie) intake - energy expenditure

Overweight and obesity are influenced by many factors including hereditary tendencies, environmental and behavioural factors, ageing and pregnancies [6]. What is clear is that obesity is not always simply a result of overindulgence in highly palatable foods or of a lack of physical activity. Biological factors (hormones, genetics), stress, drugs and ageing also play a role. However, dietary factors and physical activity patterns strongly influence the energy balance equation and they are also the major modifiable factors. Indeed, high-fat [7], energy-dense diets [8, 9] and sedentary lifestyles [10, 11] are the two characteristics most strongly associated with the increased prevalence of obesity world-wide. Conversely, weight loss occurs when energy intake is less than energy expenditure over an extended period of time. A restricted calorie diet combined with increased physical activity is generally the advice proffered by dieticians for sustained weight loss [12].

Miracle or wonder diets that severely limit calories or restrict food groups should be avoided as they are often limiting in important nutrients and/or cannot be sustained for prolonged periods. Besides, they do not teach correct eating habits and can result in yo-yo dieting (the gain and loss of weight in cycles resulting from dieting followed by over-eating). This so called yo-yo dieting may be dangerous to long-term physical and mental health. Individuals should not be over ambitious with their goal setting as a loss of just 10% of initial weight will bring measurable health benefits [13]. What are the trends in obesity and overweight? Evidence suggesting that the prevalence of overweight and obesity is rising dramatically worldwide and that the problem appears to be increasing rapidly in children as well as in adults. The most comprehensive data on the prevalence of obesity worldwide are those of the World Health Organisation MONICA project (MONItoring of trends and determinants in CArdiovascular diseases study) [14]. Together with information from national surveys, the data show that the prevalence of obesity in most European countries has increased by about 10-40% in the past 10 years, ranging from 10-20% in men and 10-25% in women [15]. The most alarming increase has been observed in the Great Britain, where nearly two thirds of adult men and over half of adult women are overweight or obese [16]. Between 1995 and 2002, obesity doubled among boys in England from 2.9% of the population to 5.7%, and amongst girls increased from 4.9% to 7.8%. One in 5 boys and one in 4 girls is overweight or obese. Among young men, aged 16 to 24 years, obesity increased from 5.7% to 9.3% and among young women increased from 7.7% to 11.6% [17]. The International Obesity Task Force monitors prevalence data (www.iotf.org).

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References: European Food Information Council (EUFIC) Date last updated: 18 November 2006