Lecture 6 - Obesity Flashcards
What is obesity?
What is overweight?
Obesity es excess body fat resulting in a significant impairment in health
Obesity refers to an over fat level that brings with it increased risks of serious and fatal diseases
Overweight indicates too much body weight for a given height and frame
A person can be overweight without being obese.
Defining obesity - body mass index [BMI]
The standard classification of BMI recommended by the WHO for adults is based on the association between BMI and illness and mortality, and is as follows:
- underweight: BMI <18.5
- healthy weight: BMI >18.5 and BMI <25
- overweight but not obese: BMI >25 and BMI <30
- Obese class I BMI 30 - 34.9
- Obese class II BMI 35 - 39.9
- Obese class III BMI >40
BMI= weight[kg] / height [metres2]
Other methods include waist/hip ratio, underwater weighing, ski folds measurements, bio electrical impedance, dual energy X-ray absorptiometry [DEXA]
Current position - Globally
Number of people who are obese is rising rapidly worldwide - one of the fastest developing public health problems - WHO described as “worldwide epidemic”
WHO estimates 1.9 billion people globally are overweight and that over 600 million of these are obese
IASO/IOTF estimate that up to 200 million school aged children are either overweight or obese, of those 40-50 million are classified as obese
TV viewing, preference for takeaway and prepared foods, more computer bound sedentary jobs, reduced sport and physical exercise.
Obesity in Australia:
Aus obesity rates among highest in the world [3 in 5 Australian adults being obese]
O can cause a range of health problems and adds to Australia’s health costs significantly
In 2014-2015, 63.4% of Aus adults were overweight or obese [11.2million people]. This is similar to the prevalence of overweight and obesity in 2011-12 [62.8%] and an increase since 1995 [56.3%]
Rates of childhood obesity in Australia are one of the highest amongst developed nations, 1 in 4.
- 2014-15, 27.4% of children aged 5-17 were overweight or obese, similar to 2011-12 [25.7%]
Health risks of Obesity: Chronic disease
Coronary heart disease - men already suffer twice the rate of heart disease
High BP - small weight loss will cause a reduction
Stroke
Type 2 diabetes - 3x more likely to develop T2DM
Abnormal blood fat
Metabolic syndrome
Cancer
Osteoarthritis - physical strain of carrying excess weight
Sleep apnea
Obesity hypoventilation syndrome
Reproductive problems - in women
Gallstones and fatty liver
Psychological: guilt, unworthiness, rejection. Coping with society’s negative views of overweight people.
Cost of obesity
Obesity in Aus in 2011-2012 was $8.6 billion
- $3.8 billion = direct health costs
- $4.8 billion = indirect health costs
The prevalence cost per year for each obese adults has been estimated at $1780
If no further action is taken to stop the growth in obesity, this report projects that there will be a total of $87.7 billion in additional direct and indirect costs to aus accumulated across the 10 years to 2025
Development and physiology of obesity:
Number of mechanisms suggested as causes of obesity and many interrelated causes
Energy balance appears to be regulated by complex system that may be disturbed in various ways to produce obesity
Genetic factors are clearly involved - also environmental factors
Many genes are thought to be involved in the development, thus not 1 single gene the cause
Still immense debate over which factors are most important in driving population changes in obesity prevalence
Energy expenditure
Basal Metabolic Rate [BMR]
- the measurement of energy expenditure in the body under resting, post-absorptive conditions
- lowest rate of energy expenditure other than sleeping
- basal energy expenditure [BEE] represents BMR over 24 hrs
- 60-75%
Resting Metabolic Rate [RMR]
- the energy required to drive all physiological processes while in a state of rest
- BMR + small amounts of energy expenditure attributed to eating, previous muscular activity
- Resting Energy Expenditure [REE] represents RMR over 24 hrs
RMR slightly > BMR
Thermos Effect of Food [TEF]
- Energy needed to absorb, transport, store and metabolise the food consumed after a meal
- increases after a meal
- Macronutrients produce varying TEF
- Mixed meal ~ 5-10% increase in energy expenditure
Thermos Effect of Exercise [TEE]
- Increased muscular contraction during exercises produces additional heat and increases energy expenditure
- 15-30%
Thrifty Gene Hypothesis
- According to the hypothesis, the “thrifty” genotype would have been advantageous for hunter-gatherer populations, especially child-bearing women, because it would allow them to fatten ore quickly during times of abundance
- Fatter individuals carrying the thrifty genes would thus better survive times of food scarcity
- Result is widespread chronic obesity and related health problems like diabetes
- Australian Aborigines, Pima indians and Nauru Islanders are groups that are susceptible to this form of obesity.
Epigenetics/epigenome
Epigenetics is the study of gene expression or changes in appearance [phenotype], due to environmental conditions.
The epigenome can be affected by environmental conditions, while the genome is unchangeable [the epigenome interprets the DNA in the genome]
Epigenetics changes may occur within one generation. Genomic change occurs over many hundreds of thousands, even millions of years
Epigenetics code gives the genome a level of flexibility that extends beyond the fixed DNA code - allows certain types of information to be passed to offspring without having to go through the slow processes of random mutation and natural selection
Leptin and Obesity
- Leptin is a fat cell-specific hormone that functions as a signalling molecule between adipose tissue and the brain to complete the negative feedback loop of the lipostatic theory of weight control
- Produced by OB gene
- Direct correlation between amount of body fat and circulating levels of leptin
- Leptin activates the anorexigenic axis [appetite suppresion] in the hypothalamus
- Leptin acts centrally to decrease food intake and molecule glucose/fat metabolism
Body fat & Leptin
As you gain weight, fat cells produce more leptin - hypothalamus - decrease hunger and increase REE to counter weight gain
Alternatively, you try to lose weight by dieting
- Dieting
- Lose a few kilograms and decrease body fat
- When body fat stores are low, less leptin is produced
- Lower levels of leptin are released in the blood, less circulates to the hypothalamus, therefore more Neuropeptide Y [NPY] is produced
- NPY potent stimulator of food intake, reduces REE
- Thus resisting the effects of the diet & weight is regained
Leptin & Obesity
Obese people - higher blood [leptin]
- more and bigger adipose cells
- leptin higher in women
Extra leptin is ineffective
- leptin-resistant …Why?
- small changes in leptin may not be meaningful
Rather than an excess leptin telling us to stop eating:
- a lack of leptin may tell us to start eating
Irisin & obesity:
Brown vs white fat cells:
- irisin then travels around the body and modifies far cells by increasing the number of brown fat cells and reducing the number of white fat cells.
- this is good because brown fat cells burn fat while white fat cells store fat
- and the brown fat cells keep burning fat after you finished exercise
- simply put, exercise burns fat and helps create fat burning brown fat cells, courtesy of irisin
- wait, there’s more, irisin also help to fight insulin resistance, one key factor behind high blood glucose levels and type 2 diabetes.
- Active muscles produce hundreds of proteins, some doubtless acting as hormones, so irisin ah be only one of a family of “secretory peptides” that act to keep us lean and healthy. They are part of the explanation why fit people live longer than those who watch endless hours of mind altering, light emitting machinery
Proposed stages of weight Gain:
Involves both hyperplasia and hypertrophy:
- hypertrophy occurs first
- then pre-adipocytes proliferate
- then differentiation into new adipocytes
- NB large adipocytes secrete factors which initiate differentiation
Specific depots have different types of growth:
- evidence that visceral fat cells may get larger
- whereas subcutaneous fat cells may proliferate more?
Issues with popular weight loss diets:
Promote ban a certain food or food group
Imply that food can changes body chemistry
Blame hormones for weight control
Recommend supplements or health foods for everyone
Promise quick, dramatic or miraculous weight loss
Benefits of lifestyle changes and weight loss:
Reduced cardiovascular risk:
- Reduced systolic blood pressure with weight loss of at least 2kg
- Small improvements in lipid profiles with sustained weight loss
- Reduced cardiovascular and all-cause mortality
Prevention and improved control of type 2 diabetes:
- Prevention or delayed progression of type 2 diabetes
- Improved glycemic control with a sustained weight reduction of 5kg in adults with type 2 diabetes
Improvements in other conditions:
- improvements in markers of chronic kidney disease
- reduction in obstructive sleep apnea
Improved symptoms of some conditions:
- improvements in symptoms of gastro-oesophageal reflux disorder
- reduced incontinence in women
- reduced knee pain with moderate weight loss
- improved functional mobility and physical performance in older people
Improved QOL, self-esteem and depression even if weight loss isn’t substantial
Dietitian’s Association of Australia [DAA]: 10 point plan for the treatment of overweight and obesity
- Discuss reason for the referral, the dietician‘ should roll and client’s expectation
- Assess readiness to change, motivation and social factors
- Identify risk factors and co-morbidities
- Obtain anthropometric measures, if client consents and will benefit from the process
- Assess client’s food habits, eating attitudes and untried intake
- Develop diet therapy appropriate for the client
- Develop behavioural therapy strategies
- Establish realistic goals for treatment with the client and/or their career
- Establish monitoring processes, evaluate progress, modify management program and goals
Need to know?
Referral ? Reason ? Person’s expectations [appointment, weight loss] Readiness to change [barriers, motivators, social factors] Value placed on health Previous weight loss attempts [and why they didn’t work] Other weight related risk factors Food habits Cooking and shopping behaviours High energy foods Nutrient intake Cultural aspects Alcohol intake
Dietary recommendations for weight loss:
A modest reduction in energy intake is more sustainable in the long term
Increase lean protein, especially from plant sources to enhance satiety from a meal and reduce sugar cravings
Reduce portion size of energy dense foods and intake of fast foods
Maintain an adequate intake of omega 3 and 6 fats
Eat more vegetarian meals
Increase intake of fibre
Eat a more”Mediterranean”-style diet
Intake of more pro-and prebiotics
Avoid skipping meals, especially breakfast
Individual education and skills training:
Cooking program Nutrition education Physical activity Behaviour modification Supermarket tours
Establish Realistic Goals
How much weight loss is appropriate to aim for?
‘Ideal’ weight probably unachievable
- MAINTAIN [dont put on more] = this may be the best option in some cases
-LOSE 5-10% = even this results in 20% less mortality, 10mmHg drop in BP, 15% lowering of lipids/cholesterol, etc.
Factors that may contribute to weight gain:
Medication & other factors
Antispychotics Beta blockers Insulin Lithium Pizotifen Sodium valproate Tricyclics antidepressants Anabolic steroids
Smoking
Readiness to change
Cost
Barriers
Gastric binding:
Gastric banding procedure: serves only to restrict and decrease food intake [doesn’t interfere with the normal digestive process]
This small passage delays the emptying of food form the pouch and causes a feeling of fullness
The band can be tightened or loosened over time to change the size of the passage
- initially punch holds ~30ml food
- can expand later to ~60-90ml
ACSM Guidelines:
Greater amounts of PA are likely to be needed to achieve weight loss and prevent weight gain in adults:
Prevent weight gain:
- 150-250 min/week of moderate-intensity physical activity is associated with prevention of weight gain
- more than 150min/week of mod-int PA is associated with modest weight loss
Weight loss:
- 150-250min/week of mod-int PA provides only modest weight loss
- greater amounts [e.g.>250] provide clinically significant weight loss
For maintenance after weight loss:
- there is some evidence that >250min/week of mod-int PA will prevent weight gain
Energy/diet restriction coming with PA will increase weight loss as compared with diet alone
Guidelines for achieving and maintaining weight loss: Achieving weight loss
- Negative calorie balance = increase exercise and decrease calorie intake to create a negative energy balance of 500-100 kcal.d
- Exercise Recommendations = exercise 5-7d.wk for 30-60min.d, beginning with moderate intensity [40-59% VO2 or HRR]
=total duration of mod-int exercise should be >150min.wk and progress to >300min.wk [intensity is vigorous, duration maybe proportionally less]
=include RT as part of an overall exercise plan - Dietary Recommendation = reduce calorie intake to accomplish negative calorie balance in combination with exercise
=maintain a well-balanced diet composed of fruits, vegetables, whole grains, and lean protein sources
=keep dietary fat <30% of total calories, with reduction in saturated and hydrogenated sources for health benefits
Maintaining Weight loss:
- continue appropriate dietary and exercise patterns as permanent behaviour change
- duration of mod-int exercise should be >250 min.wk
