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NFS284 Chapter 7 Lecture Notes

8 Pages

Nutritional Science
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Tom Wolever

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NFS284 Chapter 7 – Energy balance and weight management Slide 4 If BMI is too high or too low, then increased risk of mortality. Slide 5 Globesity We are seeing this globally, instead of just being a characteristic of developed worlds. This emphasizes the fact that obesity (BMI > 25) is a global problem. Slide 6 The relationship between body weight and various risk factors for health. These risks to heatlh all increase as body weight increases. Slide 8 Prostate cancer Lung cancer is a consequence of cigarette smoking than nutrition. Prostate cancer doesn't have as strong of an association with obesity in terms of developing the disease, compared to the other cancers. Slide 9 The mutations change the cell in a number of different ways. They cause de-differentiation of cells and cells become proliferative (rapidly dividing). A normal cell has a stop signal, which are lost in the transition from a normal to a cancerous cell. If the cell cannot repair its own DNA, it will induce cell death. It will kill itself rather than perpetuate damaged DNA. This is how a normal cell behaves, but a cancer cell keeps growing. The cell tends to break through the local environment (e.g., basement membrane). Tumors are able to secrete proteins that dissolve the barrier very readily. The cells can go into circulation. Only 1 in 1000 cells that go into circulation actually develop into tumors in other parts of the bodies. Slide 10 What is the link between obesity and cancer? There are two link: (1) Some of the things in our diet may be carcinogenic and (2) Different diets promote cell proliferation. Colon cancer and breast cancer relate to how changes in metabolism during obesity promote the development of growth factors. Dietary conditions can change the level of SHBG. You want SHBG to be as high as possible from the point of view of breast cancer prevention. Slide 11 Obesity increases the risk of insulin resistance. FFA are very ready source of energy for the muscle. The muscle becomes lazy at taking up glucose, called insulin resistance. The pancreas has to secrete more insulin to maintain to move the glucose transporters to the surface of the cell and to maintain normal blood glucose levels. Adipose tissue is a source of estrogen synthesis. Free estrogen is circulating in the blood and readily taken up by breast cancer cells. Slide 12 Observational studies only show association. The more observational studies are repeated and the more consistent the observation, the more likely the association may have a causal link. One of the benefits of an observational study is that it can be conducted for a longer period of time to be able to measure a disease outcome. Intervention trials tend to support this data but can't measure disease outcome. You can use surrogate/intermediate markers of disease. You can biopsy colon tissue and measure proliferation rates in different cells from individuals who have different BMI or consume different diets. Slide 13 30% increase in risk with an increase in BMI. Slide 14 Gall stones form in the narrow ducts that lead from the gall bladder to the liver or to the intestinal tract. Usually treated by the removal of the gall bladder. Slide 21 90% Slide 22 Unhealthy body weight is associated with increased health risk. Weight stigmatization. Slide 24 Most people are in positive energy balance. The positive energy balance is very small and the weight gain is very gradual. Slide 27 All energy expenditure in the body is cellular metabolism. Slide 28 ATP is used for basal metabolism, which is needed to stay alive. The amount of energy expended per day. It is a daily energy use. It is called a rate because it is per unit time. The basal metabolic rate decreases with weight loss because body size is getting smaller, but our physiology is good at detecting weight loss. It interprets weight loss as starvation, so it downregulates energy expenditure (e.g., conserve body energy). The body is more efficient in how it uses its energy, so it makes it harder to lose weight. Slide 29 There is individual variation in how much people fidget. It can result in the expenditure of "enough" calories. You can be more or less physically active. This is where you have the most discretion in terms of increasing your energy expenditure. You can reduce your energy intake by eating less. You can increase your energy expenditure by moving more. Slide 30 Our body temperature increases after eating because we are expending energy. The energy expended varies with the macronutrients. We are efficient at fat and carbs. We less efficient at protein because we spend more energy to absorb protein. Slide 31 We store a 24 hour supply of glucose. We store enough fat to stay alive (e.g., provides enough calories, but not nutrients) for 57 days. Slide 33 The protein and carbohydrates are mostly used to meet the needs of the organism. The fat usually gets leftover and gets stored in the adipose tissue. If you are in extreme energy balance, you can be converting carbohydrates into fat. Slide 34 The major contribution to adipose tissue comes from dietary fats. The minor contribution to adipose tissue comes from carbohydrates and protein. Slide 35 Celluar metabolism. At the systemic level, this maintains the function of vital organs, fuels physical activity and the absorption of food. Hierarchy of nutrient use. Dietary fats are stored when there is a positive energy balance. Slide 39 Body composition is divided up into two parts: lean tissue and fat tissue. The older person has a higher body weight that is made up of fat. Slide 44 Visceral fat is a rapid source of energy. This is fine if you are in negative energy balance. This forces the pancreas to pump out more insulin because fat has to take up glucose. You can be apple- or pear-shaped irrespective of gender. Men tend to carr
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