Obesity: Causes, consequences and interventions

Question 1

What is BMI?

Answer 1

Body mass index : weight (kg) / height m²

Question 2

What BMI constitutes as being obese?

Answer 2

Above 30 kg/m²

• Obese I = 30-34.9
• Obese II = 35-39.9
• Obese III = 40+ (morbidly obese)

Question 3

What BMI is healthy?

Answer 3

18.5 - 24.9 kg/m²

Question 4

What are the problems with BMI?

Answer 4

• Doesn’t allow for difference in weight between muscle and fat
• Doesn’t consider location of fat

Question 5

Why is waist circumference important?

Answer 5

It considers the location of fat, abdominal fat predicts some conditions (eg. type-2 diabetes) and associated with CV risk

Question 6

How can you measure percentage body fat?

Answer 6

• Skinfold calipers
• Bioelectrical impedance
• Hydrostatic weighing
• DEXA - dual energy x-ray absorptiometry

Question 7

What are percentage body fat thresholds for men and women?

Answer 7

Men = 25%

Women = 32%

Question 8

How does hydrostatic weighing work?

Answer 8

Bone and muscle are denser than water so someone with a larger percentage of fat free mass will weigh more in the water and have a lower % body fat

Question 9

How does dual energy X-ray absorptiometry (DEXA) work?

Answer 9

Divides body into total body mineral, fat-free soft mass and fat tissue mass

Question 10

How much is life expectancy reduced by grade I obesity (bmi 30-34.9)?

Answer 10

Reduced by 3 years

Question 11

How much is life expectancy reduced by grade III/Morbid obesity (bmi 40+)?

Answer 11

By 8-10 years, equivalent to effects of lifelong smoking

Question 12

What are main health risks associated with obesity?

Answer 12

• Some cancers: eg. breast, colon
• Musculoskeletal: osteoarthritis, lower back pain
• Circulatory: high BP, CHD, DVT
• Metabolic/Endocrine: T2 Diabetes, cholesterol, metabolic syndrome
• Repro/Uro: Stress incontinence, menstrual abnormalities, infertility, erectile dysfunction
• Respiratory: sleep apnoea, asthma
• Non-alcoholic fatty liver disease
• GI disease: gall stones
• Psychological and social problems: stress, depression, low selfesteem

Question 13

Are men or women more likely to gain abdominal fat?

Answer 13

Men

Question 14

What 4 theories underly the causes of obesity?

Answer 14

• Genetic
• Economic
• Behavioural
• Psychological

Question 15

What two studies support than genes are related to obesity?

Answer 15

1. Twin studies: Obesity far more similar in identical twins reared apart than in non-idential twins reared together
2. Adoptee studies: Adoptee’s weight far more strongly related to biological parents

Question 16

How likely will a child be obese if they have

(i) one obese parent
(ii) two obese parents
(iii) healthy BMI parents

Answer 16

(i) 40%
(ii) 80%
(iii) 7%

Question 17

What does the metabolic theory suggest in regards to genetic vulnerability?

Answer 17

Resting metabolic rate is heritable and is associated with weight gain, however RMR is now lower in obesity.

Question 18

What does the fat cell theory suggest in regards to genetic vulnerability?

Answer 18

Cell number mainly genetically determined, severely obese have larger and more cells, can increase number of cells especially in childhood

Question 19

What does the appetite theory suggest in regards to genetic vulnerability?

Answer 19

Leptin regulates appetite, lack of evidence to show that obese produce less leptin

Question 20

What does the economic theory suggest about obesity?

Answer 20

Cost of food as a proportion of our expenditure has decreased, high energy food are cheaper and time to prepare a meal has been reduced.

Question 21

What are the behavioural explanations for obesity?

Answer 21

How the intake of food is greater than energy expanded, so eating more than burning.

Some evidence for obese eating more fats relative to carbs, and eating more foods with high glycemic index.

Question 22

Do the obese eat for different reasons than non-obese?

Answer 22

Unsubstantiated theory that obese respond more to external cues (sight of food) than to internal cues (hunger)

Question 23

What are the reasons for a societal reduction in physical activity?

Answer 23

• Work patterns
• Technology
• Transport

Question 24

What are the psychological explanations for obesity?

Answer 24

• Thinness associated with attractiveness
• Aversion to fat
• Stigma/blame
• Low self-esteem, poor self-image
• Is depression higher in obese?
• Attitudes and beliefs associated with eating and PA levels

Question 25

What are some cognitive-behavioural strategies for weight reduction?

Answer 25

• Self-monitoring
• Stimulus control
• Relapse prevention

Question 26

What does an effective diet consist of?

Answer 26

• Energy restricted
• Low glycaemic index
• Lower carb
• Lower fat

Question 27

Are pharmaceuticals effective for weight reduction?

Answer 27

• Orlistat, sibutramine and rimonabant in trials > 1 year
• High attrition rates
• All medications modestly effective in reducing weight and have differing effects on cardiovascular risk profiles

Question 28

Is surgery effective for weight reduction?

Answer 28

• Bariatric surgery results in greater weight loss and reduces weight associated comorbidities compared with non-surgical interventions