Activity, diet and weight control
This will focus on why dieting alone is not a successful strategy for weight control. There is a clear relationship between physical activity and measures of body composition such as waist to hip ratio, waist circumference and body fat. Yet data from the Health Survey for England shows that in 2004 only one-third of men and one-quarter of women were taking thirty minutes of exercise at least five times a week (NHS, 2006). Low levels of physical activity are associated with poor diet and obesity, which may in turn be a barrier to being active (Skidmore, 2007). According to NHS statistics (NHS, 2006) the main reasons given by adults for not participating in active sports during the last year were: their health wasn’t good enough (50 per cent), followed by difficulty in finding time (18 per cent) and not being interested (15 per cent). In this unit we will consider why this inactivity is of concern in relation to healthy weight and why physical activity is a key component for weight loss and weight maintenance.
Physical activity influences appetite and leads to improved overall fitness levels. In turn, higher fitness levels mean you gain advantages that benefit your weight control, because of the increased use of body fat as an energy source, without losing lean muscle mass. One of the major physiological advantages of exercise is that levels of fat in the blood are reduced. We will consider how exercise can influence cholesterol in the blood, and therefore reduce the risk of coronary heart disease (CHD).
How much energy is used during activity is related to several factors including the duration and intensity of the exercise. For effective weight control, Sharkey and Gaskill recommend moderate rather than high intensity exercise, because more calories are used before exhaustion is reached. Others emphasise that intensity alone is not so important, and it is the total energy expenditure (duration and intensity) that is more relevant. Sharkey and Gaskill also emphasise that greater fitness allows more activity and therefore more weight control, hence frequency may be more important than intensity. Exercise may be more effective than dieting because of the excess post-exercise oxygen consumption (EPOC), where calorie expenditure remains high for a short while after the period of exercise (the recovery period).
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