Obesity, physical activity and health

Over the past 25 years the prevalence of overweight or obesity doubled in American children ages 6 to 11 years of age and tripled in American adolescents' ages 12 to 17 years (8). A 75% relative increase in obesity in adolescents is noted from 1970 to the present and currently 25% of American adolescents are identified as being obese (9). The increase in childhood and adolescent obesity has resulted in increases in obesity or overweight in adults.

Approximately 80% of overweight adolescents become overweight adults. Recent research notes that the prevalence of obesity among Americans 18 to 29 years of age is 14%, up to 21% if they had some college education; perhaps 35% of American college students are now overweight (10).

All these sobering statistics put together shows that obesity and over weight is a plague on humanity and therefore need a drastic approach at correcting this menace!

In addition some notable health problems have been associated with being obese or overweight. For instance, type II diabetes mellitus, cardiovascular diseases such coronary heart disease, hypertension, poor cognitive functioning, sedentary lifestyle and others.

All these problems complicate life and results in reduced life expectancy in adults. While for an obese or overweight adolescent, 'obesity compounds a common adolescent problem of low self-esteem and can disrupt psychosocial development, interfering with the normal process of adolescence, a timeless journey that prepares the child for adulthood.

An obese young person may have difficulty dealing with peers and this communication problem can seriously disrupt normal adolescent development. Psychological complications have been associated with obesity in adolescents, including depression, poor self-image, and difficulties in both the home and social environment (including school)' (11).

The overall picture of obesity and overweight seems gloomy but recent research into the realm of energy balance has a lot of hope for obese and overweight patients. 'To effectively intervene, dietetics professionals and other health care practitioners need to address both sides of the energy balance equation when counselling clients and patients' (14).

'Often, the focus on energy intake supersedes the promotion of a physically active lifestyle. Incorporating appropriate and sufficient physical activity into one's life is an essential component of achieving and maintaining a healthful body weight' (6).

Traditionally, exercise has been viewed as a universal panacea, providing a wide range of both physical and psychological benefits. Moderate amounts of physical activity have been shown to reduce the risk of premature mortality from all causes (12) and from coronary heart disease specifically. Numerous studies have linked regular physical exercise with improvements in the function of muscles and joints, achieving peak bone mass, fine-tuning metabolic homeostasis, achieving endocrine and immunologic health and enhancing mental health. (6).

Increasing physical activity to achieve energy balance and prevent obesity, rather than solely reducing energy intake, offer special physiological and metabolic advantages. Physical activity may improve appetite control. Regular physical activity is known to induce favourable metabolic changes in muscles and adipose tissue that promote the use of fat for energy as opposed to storing it (6).

Physical activity enhances insulin sensitivity and improves glucose tolerance (13). Hence, research efforts have been directed toward defining the role of physical activity in the prevention and treatment of type 2 diabetes mellitus. Increased incidence of type 2 diabetes has been linked to inactivity in large population studies, and participation in lifestyle modification programs to increase physical activity leads to a reduced incidence of the disease (14).

These positive effects of physical activity may be attributed, in part, to increased skeletal muscle contractions that mimic the action of insulin, thereby increasing glucose uptake and metabolism (15).

The relationship between physical activity and cardiovascular disease has been an active area of investigation for many years. Engaging in regular exercise or moderate physical activity improves circulating lipid profiles and favourably alters lipoprotein metabolism, decreases blood pressure, reduces blood coagulation and platelet aggregation and decreases risk of cardiac arrhythmias (16).

In 1996, the surgeon General issued physical Activity and Health, a report stating that persons of all ages should accumulate a minimum of 30 minutes of physical activity of moderate intensity on most, if not all, days of the week. This amount of physical activity is roughly equivalent to expending 150 kcal per day or 1000 kcal per week. The primary outcome affected by this quantity of physical activity is decreased risk of developing chronic diseases such as diabetes and cardiovascular diseases (6).

Physical activity is recognised as an important component of weight-loss program but is most effective when combined with appropriate diet modifications (17). To prevent weight regain following significant weight loss, estimates of physical activity energy expenditure have been reported to range between 300 and 400 kcal per day (18).

Typically, reductions of 500 to 1000 kcal a day are needed to produce weight loss at the recommended levels of 1 or 2 Ib (0.45 or 0.90 kg) a week (19). Strong evidence shows that physical activity results in modest weight loss and increases cardiovascular fitness independent of weight loss. "Lifestyle" strategies that combine a controlled energy diet, increased physical activity, and behaviour therapy provide the most successful treatment for weight loss and maintenance of that weight loss (3).

It is important to know how much physical activity is required to prevent unhealthful weight gain in adults (6). A comprehensive review of the evidence suggest that the energy expended in daily physical activity be at least 80% of resting energy expenditure, an activity level equivalent to an additional 60 to 90 minutes of brisk walking in adults who normally engage in only modest amounts of physical activity (20). The recommendation of 30 minutes per day of regular, moderate-intensity activity was challenged because it was insufficient to prevent adult weight gain and fully achieve all the 60 minutes of moderate-intensity physical activity daily to promote a healthful body as well as health and vigour (21).

Ultimately control of obesity is likely to require population based strategies to promote healthy eating and increased physical activity. The most effective population based interventions are likely to adopt an integrated, multidisciplinary, and comprehensive approach and involve a complementary range of actions that work at the individual, community, environmental, and policy level (22).

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