Obesity Flashcards
What adipose tissue can lead to the most detrimental health risks?
What type of health conditions can visceral fat cause?
describe the specific effects adipose tissue around the kidney could have:
intra-organ adipose tissue - most health risk –> called visceral fat, causing metabolic disturbances
Fat on the stomach that penetrates the major organs can lead to heart disease, diabetes etc
Adipose tissue that surrounds the kidney will increase blood-pressure, renal compression may then lead to hypertension
Why is subcutaneous fat important?
How was this reversed in the mice study?
- Without it = poor health
- without SC fat = insulin resistance, diabetes, NAFLD
- surgical transplantation of subcutaneous tissue reverses all metabolic disruptions.
Define Obesity
- abnormal or excessive fat accumulation that presents a risk to health
- Typically defined by high BMI alongside other health measures e.g.: waist-circumference = high disease risk
- Doesn’t tell us where the fat is stored
What are some impacts caused by obesity and high BMI?
○ Cancers: liver, pancreatic, thyroid, kidney
○ Cardiovascular & cardiometabolic disease: heart/kidney disease, stroke
○ Musculoskeletal conditions: osteoarthritis
- the economy
What percentage of obese individuals are considered metabolically healthy?
10– 34% of obese individuals are classed as metabolically healthy
What percentage of daily movement contributes to energy output?
20-25% of energy output
What was BMI originally created for?
How is it calculated?
Used to study the health of populations, NOT individuals
Weight(kg)/Height(m squared)
Name the limitations to using BMI:
Why is it important to know where fat is stored?
How can we overcome this issue?
Doesn’t account for
* proportion of fat
* Proportion of muscle
* Proportion of bone
- can lead to incorrect assumptions about a person’s health, as athletes may have a high BMI value because they are muscular, but have low body fat .
- BMI should always be used in conjunction with waist circumference, or Waist-to-hip ratios
Provide some examples of how excess adipose tissue(obesity) can impact daily living:
- Neck fat can lead to sleep apnea (the airway closing during sleep(affects sleep))
-osteoarthritis from carrying around extra 20-30kg
-Increased pro-inflammatory cytokines (insulin resistance, in skeletal muscle) = more FFA released and are then stored in liver leading to non-alcoholic fatty liver disease, cirrhosis(scar tissue in the liver preventing proper function)
How does increased adiposity bring about type 2 diabetes?
- increased adipokine synthesis(adipose cytokines)
- increased pro-inflammatory cytokines (TNF-α, IL-6) - leads to chronic low-grade inflammation impairs insulin function
- Oxidative stress, endothelial damage, FFA release = insulin resistance, higher blood glucose
= Type 2 diabetes
–> leading to heart failure, stroke & kidney disease
How does increased adiposity cause non-alcoholic fatty liver disease?
- increased lipid production
- causes hydrolysis of TG
- release of FFA –> increasing insulin resistance, lipotoxicity & dislipidemia
= Non-alcoholic fatty liver disease, Cirrhosis
–> heart failure, stroke & kidney disease
How does increased adiposity lead to coronary heart disease?
- increased SNS activity = increase in adrenaline & FFA & GLU to blood stream
- increased activity of renin-aldosterone system = renal compression = hypertension
- increase release of inflammatory adipokines causing atherosclerotic lesions & plaque build up
= Coronary heart disease, stroke & kidney disease
What are the mechanical stresses brought about by increased adiposity?
- increased mechanical load on joints = osteoarthritis
- increased intraabdominal pressure = acid reflux disease
- increased pharyngeal soft tissue = sleep apnea
What are some limitations of the current research on BMI for populations?
How does BMI impact relative risk of premature mortality?
- Most BMI research has been conducted on white populations, which may not be as accurate for other races
- south Asians are at greater risk of developing obesity-related health conditions (such as type 2 diabetes) at a lower BMI compared to white people.
- Relative risk of premature death increases with higher BMI
- Overly low BMI also have health risks
- Having more health conditions largely increases the relative risk of premature mortality
How can adipocytes become stressed?
What type of stress can weight gain cause on the body?
what impact might this have on the SNS?
- weight gain increases their size = stress as they become hypoxic(lack O2)
- oxidative stress
- ER - stress
- endothelial damage
- free fatty acids
- adipose necrosis
- leads to macrophages recruited, which become cytokines & released by adipose tissue
The sympathetic nervous system also becomes chronically overactive causing high blood-pressure, heart disease and stroke.
Define:
monogenic obesity
- Monogenic obesity – potent effect of single genes , mainly caused by heterozygous mutations in the melanocotin-4 receptor gene
- relates to the leptin-melanocortin signalling pathway in the hypothalamus which causes extreme overeating and severe obesity
○ Appears in 2 to 5% of children with severe obesity, mainly in Europe - most common genes are: FTO (fat-mass and obesity associated) likely to be 1.2-3kg heavier than other people, TMEM18 (transmembrane protein 18) and MC4R (melanocortin-4 receptor) genes
Define:
Polygenic Obesity
- Polygenic obesity - combination of genes
- These genes work within neural circuits within the brain
- Found by screening the entire genome in large samples to identify if there are any single-nucleotide polymorphisms associated with BMI & obesity
- FTO gene cause a risk of 1.2-3kg increase in weight, compared to a person without the allele
- This effect on polygenic obesity is confirmed by studies, past 70yrs
Define:
sarcopenic obesity
- Sarcopenic obesity - obese individuals with high body fat but low muscle mass percentage - commonly linked to insulin resistance
How might the environment impact a person’s likely-hood to be obese?
- Industrialisation, mechanisation, transport, leisure, work, diet
- Genetic constitution unsuited to 21st century living
- ‘normal response to an abnormal environment’
- Obesity is a ‘mis-match’ disease
What amount of increase in risk do people who have sat more than 35hrs per week have, over those with <15hrs per week?
> 35 hours per week sitting down during leisure time had a 61% higher risk of obesity.
Compared to people sat less than 15 hrs per week.
Describe the gene-behaviour interaction:
A group of people are sat down in a meeting room drink tea and coffee Somebody walks in with a plate of pastries and biscuits
Four types of people….
1. The person who doesn’t even notice
2. The person who notices, thinks twice, but stays put
3. The person who has one biscuit
4. The person who eats four biscuits without realising
- Most recent study on gut hormones on weight loss
- Clinical benefits from weight loss start from 5%
How is energy balanced in the body?
- The hypothalamic arcuate nucleus contains 2 sets of neurons, which are inhibited/excited by circulating neuropeptide hormones. This regulates food intake and energy expenditure.
- Short & long-term is controlled by a coordinated network of peripheral signals from adipose tissue, stomach, pancreas etc.
- Outside the hypothalamus in the brain controls energy-balance through sensory-signal input: cognitive processes, greedy food consumption, memory and attention.
What are the classifications of BMI?
- underweight = <18.5
- normal = 18.5-24.9
- overweight = 25-29.9
- obese = 30-34.9
- very obese = >35
Describe counter balance:
When the body is exposed to a negative energy balance it can stimulate an increase in central orexigenic signals, which counterbalance the decreased energy intake by increasing appetite
