Physical Activity and Obesity
People can become obese as a result of eating too much, not being sufficiently active, or both.
Traditionally, much more attention has been directed at dietary factors than low activity levels in the search for the cause of obesity and its treatment. Surprisingly, however, the recent rapid rise in obesity (from 6 to 15.5% in males and 8 to 16% in females) has occurred at a time when total energy intake and fat consumption have declined. At the same time, there have been steady but significant changes in our activity habits. There are fewer occupations requiring significant physical work. The affordability of the motor car and energy-saving devices at home and work, and the attractiveness and availability of home entertainment and computers have contributed to less active lifestyles. It has been estimated that our energy expenditure may have reduced by as much as 30%. It is clear from dietary surveys that reductions in energy intake have not kept pace with the fall in physical activity. The result is a rapid increase in the prevalence of obesity, especially in the lower socio-economic groups.
What is Physical Activity
Physical activity refers to all energy expended by movement or locomotion. This includes acts as mundane as walking, climbing stairs and gardening. Exercise is physical activity that is intentional and purposefully designed to improve some aspect(s) of fitness or health. It can include a walking programme, but can also mean more specific activities such as aerobic dance, weight training, and a range of sports. Even active past-times such as gardening or line dancing can be considered exercise if the intention is to enhance health and well-being. Sport is a form of physical activity which involves structured competitive situations governed by rules. Physical fitness is a widely used term referring to a set of attributes such as strength and stamina that determine the individual’s ability to undertake various types of activity.
Does Physical Activity Help People to Lose Weight?
Several recent reviews have considered the effect of exercise on weight loss. Although results from studies vary, the addition of exercise to a moderate diet provides a small increment in weight loss. A small weight loss is also found when exercise is not accompanied by a diet. Taken together, this research suggests that an exercise programme involving daily walking or three or four sessions of exercise per week will produce a weight loss of approximately 1kg (2lbs) per month in overweight to mildly obese people. Although this is small with respect to most dietary strategies, increased levels of exercise also have other benefits independently of weight loss.
Many studies have demonstrated that when exercise is combined with dietary restriction the proportion of weight lost as fat is greater than dieting alone. This is because exercise conserves or even develops muscle tissue, particularly if resistance (weight) training is used. Maintenance of muscle mass by exercise helps to preserve metabolic rate. In addition, exercise helps the individual who is losing weight feel firmer and more toned than if the weight loss is through diet alone, when the body is more likely to feel saggy and baggy. This can have a positive effect on motivation and body image and perhaps improve long-term outcomes. There are clear benefits of regular exercise for people trying to lose weight. However, exercise alone is more likely to play a critical role in long-term weight control for overweight and mildly obese individuals rather than the severely obese who often find it difficult to achieve significant levels of weight-bearing movement. However, as weight is lost by other methods, exercise levels can be gradually increased.
Does Physical Activity Help People to Keep Weight Off?
Helping people sustain their weight loss remains the major challenge in obesity treatment. Although there are many treatments for obesity, the long-term success is disappointing. Regular exercise appears to be an important component of weight-loss maintenance programmes. A recent review showed that the average sustained weight loss over a minimum of 6 months was 4.0kg in 4 diet-only programmes, 4.9kg in 5 exercise-only programmes, and 7.2kg in 3 diet and exercise programmes. It is not fully established why exercise improves long-term weight loss. The extra energy expended only partially explains the effect. The maintenance of lean tissue may contribute. It is also possible that exercisers find additional motivation, either through improved body image, self-esteem, or a sense of personal control to better manage their lifestyles.
Can Physical Activity Help to Prevent Overweight and Obesity?
Given the poor long-term success in the treatment of obesity, prevention is critical. In general, active people are slimmer than sedentary people. Men and women who walk regularly, or run, cycle, golf, or dance are less likely to gain weight than inactive individuals. One study shows that the chances of 13kg of weight gain over a 10 year period are 7 times higher in sedentary women than the active group, whilst sedentary men are 3.9 times more likely to gain 8-13kgs than men who report a high level of activity. Men or women who become inactive increase their risk of weight gain.
Source: Association for the Study of Obesity.
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