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Copy all text in red. Advanced Biology Presentation. Weight Control and Obesity. The definition of obesity. ‘A chronic disease characterised by excessively high body fat in relation to lean body tissue.’. The scale of the problem. Obesity is defined by a body
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Copy all text in red Advanced Biology Presentation Weight Control and Obesity
The definition of obesity ‘A chronic disease characterised by excessively high body fat in relation to lean body tissue.’
The scale of the problem Obesity is defined by a body mass index (BMI) of greater than greater than 30kg/m2 Obesity is continuing to increase each year in both men and women.
If the increasing obesity population trend continues, it is predicted that the prevalence of obesity in the year of 2010 will be about 19% of men and 25% of women.
Obesity in Scotland 14% of men and 17% of women are classified as obese (BMI >30). Even more worryingly, about 20% of Scottish children are overweight.
Health risks of obesity There is an increased risk of: • Coronary heart disease • Stroke • Gall stones • Type 2 (non-insulin dependant) diabetes • Some cancers (colon;breast;possibly uterine and ovarian) • Bone and joint disorders (excess pressure on knee, ankle and hip joints) • Respiratory problems (excess weight over lungs)
Causes of obesity The causes of obesity are complex and are often interrelated. However, the two most likely causes of the steep rise in the prevalence of obesity in the last twenty years are: • the decrease in physical activity both at work and at leisure • the energy-dense (high fat) diet currently consumed. Although the average total energy intake has actually decreased over this time period, the energy output has decreased to a greater extent, resulting in a positive energy balance, which ultimately results in obesity.
Treatment of Obesity Obesity is treated by reducing energy intake, increasing energy expenditure or a combination of both. Current evidence would suggest that weight loss is more likely to be maintained if levels of physical activity are increased by permanent lifestyle changes in addition to reducing the amount of fat in the diet.
Treatment of Obesity Pyramid A small percentage of those who are obese go on to have surgery such as Gastric Bypass surgery If the person struggles to lose weight through lifestyle changes they may choose to try certain medication. Most of those who are obese make changes in there lifestyle to help reduce their weight.
Effect of exercise on body composition and weight control Individuals who maintain a physically active lifestyle tend to maintain a desirable level of body composition (12-15% fat in males, 20-30% in females).
For individual who are trying to lose weight by only reducing their food intake, the addition of exercise has many benefits: • increased energy deficit • increased relative loss of fat while preserving ‘active’ lean tissue • prevents fall in BMR which often accompanies low-energy intakes • provides significant benefits to overall health (Physical activity does not need to be strenuous to achieve these benefits)
A negative energy balance of 29.4 MJ (7000kcal) is required to lose 1kg of body fat, regardless of whether this deficit occurs slowly or rapidly. For example, a deficit of 420 kJ/day between energy intake and energy expenditure will result in the loss of 1kg after 10 weeks (420x7x10=29,400kJ), Problem 1 – How long would it take to lose the same weight with an energy deficit of 2100kJ/day? Answer - same fat loss after only 14 days (2,100x14=29,400kJ).
Example Let us assume that an individual wants to lose 10kg of body fat - this represents a total energy deficit of approximately 294MJ. • Problem 2 If the desired energy deficit is 2MJ/day (which can be achieved by increasing energy output by 1 MJ/day and reducing energy intake by 1MJ/day), how long would it take to lose 10kg It would take approximately 147 days (21 weeks) to lose 10kg of fat.
PROBLEM 3 - The same fat loss could be achieved by creating an energy deficit of only 1MJ/day. How long would this take? It would take approximately 147 days (21 weeks) to lose 10kg of fat. PROBLEM 4 Conversely, if the energy deficit was increased to 4MJ/day how long would it take to lose the same 10kg of body fat Answer - 10 weeks (294/4=74 days = approx. 10 weeks). Many nutritionists recommend a fat loss of no more than 0.5-1.0kg per week, which is achieved by an energy deficit of approximately 2-4MJ/day.
Aerobic forms of exercise of moderate intensity and reasonably long duration - e.g. Brisk walking, jogging, swimming, cycling, golf, dancing - seem to be the most effective for fat loss in addition to conferring many other health benefits. Many health authorities, including the Health Education Board for Scotland (HEBS), now recommend the accumulation of atl east thirty minutes of moderate-intensity physical activity over most days of the week.
