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group_1_presentation_1_-_obesity [2018/02/02 19:41] alagicf |
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| - | ==== Epidemiology ==== | + | ===== Epidemiology ===== |
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| ===== Evolutionary Basis of Obesity ===== | ===== Evolutionary Basis of Obesity ===== | ||
| - | **Human babies and the need for fat** | + | ===Human babies and the need for fat === |
| Human babies have the highest percent fat at birth for mammals.<sup>[13]</sup> They have 15% body fat at birth. The second highest mammal for body fat % is the guinea pig, with 10.8. Adipose tissue is used as insulation to prevent heat from escaping the body. Human beings are hairless mammals, and therefore, are exposed to environmental stressors more directly then say a polar bear. The fur a polar bear has allows it to survive at temperatures as low as -69 degrees Celsius, even though they have a lower fat percentage than humans. Another reason humans require a high fat percentage at birth is because of the size of their brains. It is estimated that the infant brain consumes 50-60% of its total metabolic expenditure.<sup>[14]</sup> The brain is not only an expensive organ, but it is also a sensitive one. It requires lots of fat to maintain itself and grow, as well as insulation to keep it at a steady temperature of around 38 degrees Celsius. This explains our natural tendency to store fat more effectively than other mammals. | Human babies have the highest percent fat at birth for mammals.<sup>[13]</sup> They have 15% body fat at birth. The second highest mammal for body fat % is the guinea pig, with 10.8. Adipose tissue is used as insulation to prevent heat from escaping the body. Human beings are hairless mammals, and therefore, are exposed to environmental stressors more directly then say a polar bear. The fur a polar bear has allows it to survive at temperatures as low as -69 degrees Celsius, even though they have a lower fat percentage than humans. Another reason humans require a high fat percentage at birth is because of the size of their brains. It is estimated that the infant brain consumes 50-60% of its total metabolic expenditure.<sup>[14]</sup> The brain is not only an expensive organ, but it is also a sensitive one. It requires lots of fat to maintain itself and grow, as well as insulation to keep it at a steady temperature of around 38 degrees Celsius. This explains our natural tendency to store fat more effectively than other mammals. | ||
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| An important question remains: If obesity is such a detrimental condition to the human population, then why is it so evident today? | An important question remains: If obesity is such a detrimental condition to the human population, then why is it so evident today? | ||
| - | **Theory One** | + | === Theory One === |
| Evolutionarily speaking, the ability to store fat is quite the effective adaptation. Food supplies could be abundant one day, and depleted the next. This is why it is believed that another major reason for fat storage in humans is in fact an energy reserve.<sup>[15]</sup> Although obesity is quite the pandemic in many developed nations today, it was rare throughout our evolutionary history within primitive populations. In fact, there is evidence to suggest no obesity within traditional hunting and gathering populations.<sup>[15]</sup> Regardless, those with genes that promoted greater storage of fat had a higher likelihood to survive when resources became scarce. This has led to evolutionary pressures to select for genes doing just that. In the next section concerning gender and obesity, this is elaborated in more detail. | Evolutionarily speaking, the ability to store fat is quite the effective adaptation. Food supplies could be abundant one day, and depleted the next. This is why it is believed that another major reason for fat storage in humans is in fact an energy reserve.<sup>[15]</sup> Although obesity is quite the pandemic in many developed nations today, it was rare throughout our evolutionary history within primitive populations. In fact, there is evidence to suggest no obesity within traditional hunting and gathering populations.<sup>[15]</sup> Regardless, those with genes that promoted greater storage of fat had a higher likelihood to survive when resources became scarce. This has led to evolutionary pressures to select for genes doing just that. In the next section concerning gender and obesity, this is elaborated in more detail. | ||
| - | **Theory Two** | + | === Theory Two === |
| Obesity was often perceived as a status of wealth and power.<sup>[15]</sup> This is because only those who had access to high energy foods on a year round basis were able to actually become overweight. This would have lead it to be a desirable trait of the opposite sex over evolutionary time. | Obesity was often perceived as a status of wealth and power.<sup>[15]</sup> This is because only those who had access to high energy foods on a year round basis were able to actually become overweight. This would have lead it to be a desirable trait of the opposite sex over evolutionary time. | ||
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| ===== Pathophysiology ===== | ===== Pathophysiology ===== | ||
| - | **Macronutrients Vs Micronutrients** | + | === Macronutrients Vs Micronutrients === |
| Macronutrients Vs Micronutrients | Macronutrients Vs Micronutrients | ||
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| Micronutrients on the other hand are needed in smaller quantities and are essential for various chemical reactions in the body.<sup>[18]</sup> These include vitamins and minerals.<sup>[18]</sup> Vitamins allow for normal growth and metabolism as well as cellular functions.<sup>[18]</sup> These may be fat-soluble vitamins which are stored in the fatty tissues such as Vitamins A, D, E and K.<sup>[18]</sup> They may also be water-soluble which are excreted in the urine and must be taken daily such as Vitamins B and C.<sup>[18]</sup> Minerals are ionized in the body, for instance iron, sodium and potassium.<sup>[18]</sup> | Micronutrients on the other hand are needed in smaller quantities and are essential for various chemical reactions in the body.<sup>[18]</sup> These include vitamins and minerals.<sup>[18]</sup> Vitamins allow for normal growth and metabolism as well as cellular functions.<sup>[18]</sup> These may be fat-soluble vitamins which are stored in the fatty tissues such as Vitamins A, D, E and K.<sup>[18]</sup> They may also be water-soluble which are excreted in the urine and must be taken daily such as Vitamins B and C.<sup>[18]</sup> Minerals are ionized in the body, for instance iron, sodium and potassium.<sup>[18]</sup> | ||
| - | **Types of Adipocytes** | + | === Types of Adipocytes === |
| <box 28% round right | > {{ :fattissue.png?300|}} </box| Figure 5:Yellow adipose tissue in paraffin. | <box 28% round right | > {{ :fattissue.png?300|}} </box| Figure 5:Yellow adipose tissue in paraffin. | ||
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| Brown adipocytes are found in almost in all mammals and they function to dissipate energy through thermogenesis.<sup>[22]</sup> Their characteristic brown appearance is due to a high number of iron-containing mitochondria.<sup>[22]</sup> BAT develop from the middle embryonic layer, the mesoderm, which is also the source of muscle cells and adipocytes.<sup>[20]</sup> It is abundant in newborns as well as metabolically active adult humans, however, its prevalence decreases in humans as they age.<sup>[20]</sup> Furthermore, brown adipocytes also contain more capillaries than white fat, which allows for tissue to be supplied with more oxygen and nutrients.<sup>[22]</sup> In this way, produced heat can easily be distributed throughout the body.<sup>[22]</sup> | Brown adipocytes are found in almost in all mammals and they function to dissipate energy through thermogenesis.<sup>[22]</sup> Their characteristic brown appearance is due to a high number of iron-containing mitochondria.<sup>[22]</sup> BAT develop from the middle embryonic layer, the mesoderm, which is also the source of muscle cells and adipocytes.<sup>[20]</sup> It is abundant in newborns as well as metabolically active adult humans, however, its prevalence decreases in humans as they age.<sup>[20]</sup> Furthermore, brown adipocytes also contain more capillaries than white fat, which allows for tissue to be supplied with more oxygen and nutrients.<sup>[22]</sup> In this way, produced heat can easily be distributed throughout the body.<sup>[22]</sup> | ||
| - | **Normal Function of Adipose Tissue & Adipose Tissue Development** | + | === Normal Function of Adipose Tissue & Adipose Tissue Development === |
| Adipose tissue is an endocrine organ which is mainly responsible for energy storage as well as the synthesis and secretion of several hormones.<sup>[23]</sup> Adipose tissue is a major source of free fatty acids. Free fatty acids (FFA) are liberated from lipoproteins by lipoprotein lipase, allowing it to enter the adipocyte where it is reassembled into triglycerides by esterifying it onto glycerol. Adipocytes have an important physiological role in maintaining triglyceride and FFA levels.<sup>[23]</sup> | Adipose tissue is an endocrine organ which is mainly responsible for energy storage as well as the synthesis and secretion of several hormones.<sup>[23]</sup> Adipose tissue is a major source of free fatty acids. Free fatty acids (FFA) are liberated from lipoproteins by lipoprotein lipase, allowing it to enter the adipocyte where it is reassembled into triglycerides by esterifying it onto glycerol. Adipocytes have an important physiological role in maintaining triglyceride and FFA levels.<sup>[23]</sup> | ||
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| ===== Hormones ===== | ===== Hormones ===== | ||
| - | **Endorphin release when you eat** | + | === Endorphin release when you eat === |
| When energy-dense or high calorie food is consumed, endorphins and enkephalins are released in the brain, which are the brain’s natural opioids. Consuming fats and sugars essentially triggers shifts in the brain that are associated with addictive drugs such as heroin. This then stimulates dopamine release into the nucleus accumbens in the midbrain. Subsequently, this creates a feeling of reward.<sup>[26]</sup> Fast food meals can be extremely high in calories and can contain almost all of the recommended caloric daily intake for a person in a single sitting. This can cause physiological changes which may mute or alter the hormones responsible for satiety.<sup>[26]</sup> | When energy-dense or high calorie food is consumed, endorphins and enkephalins are released in the brain, which are the brain’s natural opioids. Consuming fats and sugars essentially triggers shifts in the brain that are associated with addictive drugs such as heroin. This then stimulates dopamine release into the nucleus accumbens in the midbrain. Subsequently, this creates a feeling of reward.<sup>[26]</sup> Fast food meals can be extremely high in calories and can contain almost all of the recommended caloric daily intake for a person in a single sitting. This can cause physiological changes which may mute or alter the hormones responsible for satiety.<sup>[26]</sup> | ||
| - | **Leptin** | + | === Leptin === |
| <box 28% round right | > {{ :leptin.png?300|}} </box| Figure 6: Leptin signalling effect on the brain and subsequent responses on food intake and energy expenditure. https://www.peptideclinics.com.au/wp-content/uploads/2015/01/nm1010-1100-F3.jpg > | <box 28% round right | > {{ :leptin.png?300|}} </box| Figure 6: Leptin signalling effect on the brain and subsequent responses on food intake and energy expenditure. https://www.peptideclinics.com.au/wp-content/uploads/2015/01/nm1010-1100-F3.jpg > | ||
| Leptin is produced and secreted by adipose tissue in the body.<sup>[27]</sup> To signal satiety, the fat cells release leptin into the bloodstream, which then provides a signal in the hypothalamus, promoting a feeling of fullness.3 When leptin levels fall in response to lack of food or fasting, a signal is sent back to the body by the brain to promote food intake and a decrease in energy expenditure.<sup>[28]</sup> Because leptin is produced in fat cells, leptin levels are higher in obese people. However, people who are obese are not as sensitive to leptin and are thought to have a resistance to the hormone.<sup>[27]</sup> | Leptin is produced and secreted by adipose tissue in the body.<sup>[27]</sup> To signal satiety, the fat cells release leptin into the bloodstream, which then provides a signal in the hypothalamus, promoting a feeling of fullness.3 When leptin levels fall in response to lack of food or fasting, a signal is sent back to the body by the brain to promote food intake and a decrease in energy expenditure.<sup>[28]</sup> Because leptin is produced in fat cells, leptin levels are higher in obese people. However, people who are obese are not as sensitive to leptin and are thought to have a resistance to the hormone.<sup>[27]</sup> | ||
| - | **Insulin** | + | === Insulin === |
| Insulin is a hormone produced by the beta-cells of the pancreas.<sup>[27,29]</sup> It plays a large role in the metabolism of carbohydrates and fat. Insulin maintains energy levels and ensures the body has the available energy it requires. It does this by stimulating glucose uptake in the blood from surrounding tissues.<sup>[27]</sup> When the body has the energy it needs, there is no need to consume more energy through food. In obesity, insulin signals are lost or become insensitive, therefore glucose uptake is low, and appetite suppression does not occur since there is not adequate signalling indicating the body has enough energy.<sup>[29]</sup> This can lead to the development of type II diabetes.<sup>[27]</sup> These defects may occur due to impaired insulin signalling in fat and muscle tissue, and a downregulation of the major insulin-responsive glucose receptor in fat cells, GLUT4.<sup>[29]</sup> | Insulin is a hormone produced by the beta-cells of the pancreas.<sup>[27,29]</sup> It plays a large role in the metabolism of carbohydrates and fat. Insulin maintains energy levels and ensures the body has the available energy it requires. It does this by stimulating glucose uptake in the blood from surrounding tissues.<sup>[27]</sup> When the body has the energy it needs, there is no need to consume more energy through food. In obesity, insulin signals are lost or become insensitive, therefore glucose uptake is low, and appetite suppression does not occur since there is not adequate signalling indicating the body has enough energy.<sup>[29]</sup> This can lead to the development of type II diabetes.<sup>[27]</sup> These defects may occur due to impaired insulin signalling in fat and muscle tissue, and a downregulation of the major insulin-responsive glucose receptor in fat cells, GLUT4.<sup>[29]</sup> | ||
| - | **Sex Hormones** | + | === Sex Hormones === |
| <box 28% round right | > {{ :insulin.png?300|}} </box| Figure 7: Effect of insulin on glucose uptake in the cell. | <box 28% round right | > {{ :insulin.png?300|}} </box| Figure 7: Effect of insulin on glucose uptake in the cell. | ||
| https://www.cornerstones4care.com/content/dam/nni/cornerstones4care/images/content/treatment/B-p9_About%20Diabetes%20Medicines%20%E2%80%93%20An%20Overview%20%20Cornerstones4Care_fx%201.jpg > | https://www.cornerstones4care.com/content/dam/nni/cornerstones4care/images/content/treatment/B-p9_About%20Diabetes%20Medicines%20%E2%80%93%20An%20Overview%20%20Cornerstones4Care_fx%201.jpg > | ||
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| - | **Ghrelin** | + | === Ghrelin === |
| Ghrelin is a fast-acting hormone that plays a role in stimulating appetite and reducing fat utilization.<sup>[31]</sup> It is secreted by the stomach.<sup>[32]</sup> Ghrelin sends a signal to the hypothalamus, which then stimulates appetite. Although it is expected that ghrelin levels would be higher in obese individuals since it is the hunger hormone, it has been seen that ghrelin levels are actually decreased in obese humans.<sup>[31]</sup> | Ghrelin is a fast-acting hormone that plays a role in stimulating appetite and reducing fat utilization.<sup>[31]</sup> It is secreted by the stomach.<sup>[32]</sup> Ghrelin sends a signal to the hypothalamus, which then stimulates appetite. Although it is expected that ghrelin levels would be higher in obese individuals since it is the hunger hormone, it has been seen that ghrelin levels are actually decreased in obese humans.<sup>[31]</sup> | ||
| - | ==== Environment ==== | + | ===== Environment ===== |
| Many environmental factors are at play in the development of obesity, namely high-fat diets and low levels of physical activity.<sup>[33]</sup> The WHO reports that worldwide, 23 percent of adults and 81 percent of adolescents do not get enough physical activity to prevent chronic diseases such as obesity.<sup>[33]</sup> Furthermore, in developed nations, there has been an increase in food availability, large portion sizes or “super-sizing” of commercially available foods as well as the rise of fast-food restaurants, which can all lead to overconsumption.<sup>[34]</sup> There is also an indication that people living in poverty have a higher risk of weight gain.<sup>[34]</sup> This may be because impoverished areas, often called “food deserts”, have poor access to fresh foods.<sup>[34]</sup> Additionally, the low cost of fast-food restaurants is a much more affordable option for many people of lower socioeconomic status.<sup>[34]</sup> | Many environmental factors are at play in the development of obesity, namely high-fat diets and low levels of physical activity.<sup>[33]</sup> The WHO reports that worldwide, 23 percent of adults and 81 percent of adolescents do not get enough physical activity to prevent chronic diseases such as obesity.<sup>[33]</sup> Furthermore, in developed nations, there has been an increase in food availability, large portion sizes or “super-sizing” of commercially available foods as well as the rise of fast-food restaurants, which can all lead to overconsumption.<sup>[34]</sup> There is also an indication that people living in poverty have a higher risk of weight gain.<sup>[34]</sup> This may be because impoverished areas, often called “food deserts”, have poor access to fresh foods.<sup>[34]</sup> Additionally, the low cost of fast-food restaurants is a much more affordable option for many people of lower socioeconomic status.<sup>[34]</sup> | ||
| - | ==== Genetics ==== | + | ===== Genetics ===== |
| Family history is a known risk factor of obesity and is an important predictor of obesity in children.<sup>[35]</sup> However, the heritability component of obesity is still not well understood. | Family history is a known risk factor of obesity and is an important predictor of obesity in children.<sup>[35]</sup> However, the heritability component of obesity is still not well understood. | ||
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| - | ==== Treatments ==== | + | ===== Treatments ===== |
| - | ---- | ||
| When undergoing treatment options for obesity, the combination therapy involving exercise, behavioural and dietary modifications are recommended by physicians due to their proven effectiveness and least amount of side effects. When undergoing weight loss therapy a maximum of 10% of total body weight should be lost within a 6 month period. | When undergoing treatment options for obesity, the combination therapy involving exercise, behavioural and dietary modifications are recommended by physicians due to their proven effectiveness and least amount of side effects. When undergoing weight loss therapy a maximum of 10% of total body weight should be lost within a 6 month period. | ||
| - | **Diet** | + | === Diet === |
| <box 20% round right | > {{ :diet.png?200|}} </box| Figure 8: https://d2ebzu6go672f3.cloudfront.net/media/content/images/p6_HeartFood_N1801_ts516546584.jpg > | <box 20% round right | > {{ :diet.png?200|}} </box| Figure 8: https://d2ebzu6go672f3.cloudfront.net/media/content/images/p6_HeartFood_N1801_ts516546584.jpg > | ||
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| - | **Excercise** | + | === Exercise === |
| The first component to the weight loss therapy is to treat obesity by increasing the levels of the obese individual’s physical activity.<sup>[39]</sup> The goal for any weight loss program is to have a negative energy balance at the end of the day, so the individual should aim to increase their energy expenditure and physical activity is an excellent way to do so.<sup>[39]</sup> Physical activity is linked to increased weight loss and weight management.<sup>[39]</sup> | The first component to the weight loss therapy is to treat obesity by increasing the levels of the obese individual’s physical activity.<sup>[39]</sup> The goal for any weight loss program is to have a negative energy balance at the end of the day, so the individual should aim to increase their energy expenditure and physical activity is an excellent way to do so.<sup>[39]</sup> Physical activity is linked to increased weight loss and weight management.<sup>[39]</sup> | ||
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| It is important to take note that not every exercise routine responds the same way to each individual, one type may be more effective at reducing weight for some individuals than others. There are a variety of different exercise routines which can involve running, walking, rowing, free weights or a combination of any of these.<sup>[39]</sup> It is very difficult for obese individuals to lose weight due to all of the variables associated with their weight gain and because of this it can be just as much of a mental battle as a physical one, so it is recommended that the individuals acquire a trainer that can help them with their exercise regime as well as help set realistic goals throughout the process. A meta-analysis done by Shaw et al., 2006 showed that exercise is an excellent weight loss intervention and the effects are improved with the combination of dietary modifications as well.<sup>[39]</sup> They also found that exercise was able to alleviate secondary symptoms associated with obesity like cardio vascular disease, blood pressure.<sup>[39]</sup> | It is important to take note that not every exercise routine responds the same way to each individual, one type may be more effective at reducing weight for some individuals than others. There are a variety of different exercise routines which can involve running, walking, rowing, free weights or a combination of any of these.<sup>[39]</sup> It is very difficult for obese individuals to lose weight due to all of the variables associated with their weight gain and because of this it can be just as much of a mental battle as a physical one, so it is recommended that the individuals acquire a trainer that can help them with their exercise regime as well as help set realistic goals throughout the process. A meta-analysis done by Shaw et al., 2006 showed that exercise is an excellent weight loss intervention and the effects are improved with the combination of dietary modifications as well.<sup>[39]</sup> They also found that exercise was able to alleviate secondary symptoms associated with obesity like cardio vascular disease, blood pressure.<sup>[39]</sup> | ||
| - | **Behavioural Modifications** | + | === Behavioural Modifications === |
| <box 20% round right | > {{ :screen_shot_2018-02-02_at_6.26.10_pm.png?200|}} </box| Figure 9: Illustration of Cognitive Behavioural Therapy http://stewartoncbt.co.uk/wp-content/uploads/2011/12/cbt.jpg > | <box 20% round right | > {{ :screen_shot_2018-02-02_at_6.26.10_pm.png?200|}} </box| Figure 9: Illustration of Cognitive Behavioural Therapy http://stewartoncbt.co.uk/wp-content/uploads/2011/12/cbt.jpg > | ||
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| - | **Pharmaceuticals** | + | === Pharmaceuticals === |
| Another line of treatment for obesity is to use medication in combination with the lifestyle changes mentioned above. Two popular obesity medications are in the classes of lipase inhibitors and appetite suppressants. | Another line of treatment for obesity is to use medication in combination with the lifestyle changes mentioned above. Two popular obesity medications are in the classes of lipase inhibitors and appetite suppressants. | ||
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| A retrospective study wanted to test the efficacy of the drug with adolescents. They had 25 individuals who were medicated with phentermine and they matched them with a control individual who was receiving only the standard of care.<sup>[43]</sup> They found at each measurement date 1,3 and 6 months that there was a significant difference in weight loss between groups and there was no difference in blood pressure between groups.<sup>[43]</sup> | A retrospective study wanted to test the efficacy of the drug with adolescents. They had 25 individuals who were medicated with phentermine and they matched them with a control individual who was receiving only the standard of care.<sup>[43]</sup> They found at each measurement date 1,3 and 6 months that there was a significant difference in weight loss between groups and there was no difference in blood pressure between groups.<sup>[43]</sup> | ||
| - | **Bariatric Surgery ** | + | === Bariatric Surgery === |
| Bariatric surgery is a weight loss procedure which aims to decrease the size of the obese individuals stomach by either a gastric band or the removal of a portion of the stomach.<sup>[44]</sup> It is not recommended for individuals below a BMI of 40 to undergo bariatric surgery. Post-surgery patients are only able to have a clear liquid diet which is continued until the gastro intestinal tract is healed.<sup>[44]</sup> Once that stage is complete a blended diet where foods high in protein are recommended alongside soft meals. Finally, once recovery is complete the patient is able to eat all types of foods again, but they are restricting from over eating due to the surgery. If they over eat they will reach the capacity of their stomach which will cause discomfort.<sup>[44]</sup> | Bariatric surgery is a weight loss procedure which aims to decrease the size of the obese individuals stomach by either a gastric band or the removal of a portion of the stomach.<sup>[44]</sup> It is not recommended for individuals below a BMI of 40 to undergo bariatric surgery. Post-surgery patients are only able to have a clear liquid diet which is continued until the gastro intestinal tract is healed.<sup>[44]</sup> Once that stage is complete a blended diet where foods high in protein are recommended alongside soft meals. Finally, once recovery is complete the patient is able to eat all types of foods again, but they are restricting from over eating due to the surgery. If they over eat they will reach the capacity of their stomach which will cause discomfort.<sup>[44]</sup> | ||
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| - | **Gene therapy – Leptin deficiency** | + | === Gene therapy – Leptin deficiency === |
| <box 25% round right | > {{ :gene.png?250|}} </box| Figure 11: Illustration of Gene Therapy. | <box 25% round right | > {{ :gene.png?250|}} </box| Figure 11: Illustration of Gene Therapy. | ||
| https://www.yourgenome.org/sites/default/files/illustrations/process/gene_therapy_augmentation_yourgenome.png > | https://www.yourgenome.org/sites/default/files/illustrations/process/gene_therapy_augmentation_yourgenome.png > | ||
