PBL Week 12 Flashcards
What is the physiological control of appetite?
Fatty acids from the gut are stored as white adipose tissue. After eating, the blood sugar level rises and the hypothalamus stimulates the release of insulin, which promotes the adipose tissue to uptake excess glucose. This tissue then releases leptin, a hormone that informs the hypothalamus of fullness. When fat stores are low, leptin is reduced and so we become hungry. The hunger hormone ghrelin is also stimulated in the absence of food. Furthermore, gastric stretch receptors detect distension in the stomach wall in the presence of food, which stimulated neural pathways in the brain to trigger fullness.
What are physiological effects of obesity on the body?
As people become obese, large amounts of adipose tissue builds up around the organs and under the skin. This adipose tissue becomes dysfunctional and is attacked by macrophages, leading to the release of fatty acids into the blood (lipotoxicity). This can cause insulin resistance, inflammation and an increase in risk of cardiovascular diseases. The increased insulin resistance and fatty acid levels cause more issues around the body, causing a self-perpetuating cycle. Furthermore, losing weight causes an increase in ghrelin levels; the more weight we put on, the more the body tries to maintain it or gain it back if lost.
How is fat metabolised in the body?
In the small intestine, triglycerides are emulsified by bile salts and pancreatic lipases break them down into smaller chains and then into monoglyceride molecules. CCK stimulates the release of bile and lipases. Next, the free fatty acids are transported across the instestinal membrane, but once they do they reform into triglycerides. Within the intestinal cells, they are packaged with cholesterol in phospholipid vesicles called chylomicrons, which allow these molecules to move within aqueous environments. The chylomicrons then move to the lymphatic system, which transports them to the circulatory system. They then are either transported to the liver or to be stored in adipocytes, the cells which compromise adipose (fat) tissue in the body.
Energy is obtained from fat by lipolysis, where triglycerides are first broken down in the cytoplasm of cells into fatty acids and glycerol. The resulting acids are oxidised into acetyl CoA, which is used in the krebs cycle in respiration. The glycerol enters the glycolysis pathway as DHAP. This lets each triglyceride produce far more energy than carbohydrates or proteins.
What is the role of nutrition in maintaining a healthy body weight?
The general equation for weight gain and loss is that if you eat more calories than you burn, you put on weight. The foods you eat are important too, however. Eating higher levels of fats and sugars than needed lead to the body storing them for future energy use, which is often in adipose tissue. This is the fatty tissue that creates the issues in obesity and makes us put on weight. Eating balanced meals with low levels of fats and sugars will allow your body to get the nutrients it needs while minimising weight gain.
What is the evidence that establishes a relationship between maternal obesity, foetal growth and the metabolic health of the offspring?
There are many maternal factors in obesity, both during pregnancy and at infancy. Sub-optimal diet, insulin resistance, increased free fatty acids/glucose, inflammation, hyperlidemia and maternal fat accumulation can lead to an increased leptin levels in the foetus, which alters the foetal hypothalamic development and can lead to obesity. Furthermore, behavioural changes and overfeeding can also lead to obesity in the child.
What are the classification and diagnostic methodologies used with obesity?
The main way to diagnose obesity is through the body mass index (BMI). This is measured in kg/m^2 and is calculated by dividing your weight in kg by the square of your height in meters. The NHS defines it by a BMI of over 30 signalling obesity, with a BMI of over 40 signalling severe obesity. The WHO instead breaks obesity down into classes; a BMI of 30-35 is class 1, 35-40 is class 2 and 40+ is class 3.
Additionally, obesity can also be calculated by a waist measurement; according to the NHS, a man with a waist size of 94cm or a woman with a waist size of 80cm are considered obese.
What are the treatment options for obesity?
Diets are recommended, where an obese person cuts down their caloric intake (1900 per day for men, 1400 for women) and swaps unhealthy foods for healthy alternatives. The NHS considers fad diets, such as fasting or cutting out entire food groups, unsafe; they can make you ill and don’t teach you about healthy food habits, so don’t work in the long term. Furthermore, maintaining a health weight requires plenty of exercise, too.
A doctor can also prescribe orlistat, a drug that prevents about a third of the fats in your diet from being absorbed. This must be used in conjunction with dieting and exercise. Finally, surgery is an option for some. This includes a gastric band to make the stomach smaller (so people get full quicker) or a gastric bypass, which enables some food to bypass part of the digestive system entirely. A bypass is the more effective surgery, but can lead to vitamin deficiencies, as many aren’t being absorbed.
Why do different regions in the UK have different prevalences of obesity?
This is mostly due to the wealth of different regions. Obesity has been strongly linked to poverty; lower income families often go for the cheapest meals, which tend to be quite unhealthy. Furthermore, those in poverty often work a lot and don’t have the time to cook healthy food, leading to quick, unhealthy meals or takeaways.
How can primary, secondary and tertiary prevention of disease manage childhood obesity?
Primary - measures taken before the onset of disease. Includes healthy nutrition during pregnancy, healthy lifestyle encouraged, health and nutrition policies in schools, educating population of importance of eating healthily and making unhealthy food more expensive.
Secondary - measures that lead to an early diagnosis so the disease can be treated before it becomes severe. Includes regular check ups, as well as diets and the promotion of physical activity for those who are already overweight.
Tertiary - Focuses on those who aready have the disease. Includes dieting plans, exercise plans, certain medications (e.g orlistat) and bariatric surgery.
