Obesity and Physical Activity

Question 1

Prevalence of obesity in the UK in 2014

Prediction for obesity in 2050

Answer 1

24% in men
26% in women

60% men
50% women
25% children

Question 2

what waist circumferences infer an increased risk of metabolic disease in men and women

why is waist circumference considered a good marker for increased risk

Answer 2

women:
90-110 = high
>110 = very high

men:
100 - 120 = high
>120 = very high

gives an indication of the amount of visceral fat which is prognostic marker for disease development

Question 3

Explain the process of adipose tissue acting as an endocrine organ

Answer 3

adipocytes become enlarged and then its blood supply becomes compromised

adipocyte is under oxidative stress which then causes the infiltration of immune cells

immune cells release inflammatory proteins and cytokines

further inflammatory cells are recruited, leading to chronic low grade inflammation

inflammatory proteins and cytokines get into the blood stream and have negative effects at distal sites
e.g TNF alpha and IL-6 cause insulin resistance

adipose tissue also causes itself to become inflammed and this causes the release of free fatty acids

high levels of free fatty acids cause the liver to be insulin resistant and this cause more release of free fatty acids and glucose

Question 4

Explain the link between the FTO gene and genetic predisposition to obesity

Answer 4

this gene has the same amount of impact on body weight as all other obesity linked genes combined

AA, AT, TT
AA people are on average 3kg heavier than TT
AT around 1kg heavier than TT

minor role but can easily be overcome with lifestyle

Question 5

what are the guidelines for starting people on obesity medication and for offering them bariatric surgery

Answer 5

meds = > 30 or >27+ co-morbidities

surgery = >40 or > 35 + co-morbidities

Question 6

why is PA considered to be more effective in preventing people from becoming obese than in reducing the weight of obese people
who said this

Answer 6

when obese, you are unlikely to be able to engage in sufficient amounts of PA to induce enough of an energy deficit to cause weight loss

obese = low exercise tollerance

Garrow 1995

Question 7

Physiologically why do people who were previously obese often regain weight

Answer 7

being obese has altered their physiology

body gives out strong hunger signals

Question 8

what are the three componants of daily energy expenditure and what are their rough contribtions

Answer 8

RMR = 60-70%
TEF = 10%
PA = 20% but variable

Question 9

why is it easier to be in positive energy balance than to be in negative energy balance

Answer 9

Adaptive thermogenesis

when output > input mechanisms within the body are activated which aim to make us reduce the energy deficit

Question 10

explain the study by Church et al 2011 and its findings

Answer 10

looked at trends of occupational activity in US and trends of weight gain

increase in light and sedentary occupation with a decrease in moderately active ones

linear decline in number of calories burnt via occupation

this data matched well with trends in weight gain over the same time period

Question 11

explain the study by Lee et al 2010 and its findings

give some limitations of this work

Answer 11

followed 35 000 women for 13 years, asking about weight and their PA levels

found an average of 60 mins PA per day was enough to prevent weight gain in people with BMI < 25

self report –> bias
women only

Question 12

what are the ACSM guidelines for PA needed to prevent weight gain

Answer 12

150-250 mins per week will prevent weight gain >3% in most adults

Question 13

Explain the study by Church et al 2007 and its findings

Answer 13

6 month RCT of obese and overweight post-menopausal women

no exercise
50% on NIH guidelines
NIH guidance amount
150% guidance amount

meeting of the NIH guidance for the amount of PA did not cause significant weight loss

Question 14

Explain the STRRIDE study by kraus et al 2002 and its findings

Answer 14

RCT of 159 OW/OB over 6 months

control
low amount, moderate intensity
low amount, high intensity
high amount, high intensity

found greatest weight loss was with high, high but this was still only around 2kg (despite 3000kcal per week deficit)
however this group did had a significant reduction in visceral fat so still beneficial for disease risk

Question 15

give possible reasons why exercise intervention trials often fail to see significant levels of weight loss

Answer 15

people eating more to compensate for the exercise

people avoiding lifesyle PA bc of exercise

poor adherance to exercise

intervention not sufficient enough to cause enough of an energy deficit

study period not long enough for weight loss to occur

Question 16

What did King et al 2008 demonstrate and how

Answer 16

all subjects in the trial did the same amount of exercise (30 mins 5x per week for 12 weeks)

was a large variation in the amount of weight loss between individuals.
decreases of around 10kg to some people gaining weight

subjects then divided into those who lost weight and those who didn’t
those who lost weight had not compensated for the exercise they were doing

Question 17

What are the ACSM recommendations for PA to cause weight loss

Answer 17

< 150 mins/wk = minimal weight loss

> 150 mins/wk = modest

225-420 = clinically beneficial of 5-7.5kg

Dose response relationship
Higher doses associate with clinically significant weight loss

Question 18

explain the meta analysis by Ross et al 2000 and its findings

Answer 18

compared diet and exercise as methods of causing weight loss and promote an energy deficit

Meta analysis

findings:
weight loss via diet > via exercise
in these trials the energy deficit was also greater with diet

in trials where energy deficit was the same, weight loss was also the same

Question 19

explain the concept of efficacy and effectivness as demonstrated by the meta analysis carried out by Ross et al

Answer 19

efficacy = in an ideal situation, the impact an intervention has

effectivness = the impact an intervention has in real life e.g exercise but without control of people’s diet

Question 20

explain the RCT carried out by Ross et al 2000 and its findings

Answer 20

52 OW/OB men

control
diet group (-700kcal)
exercise group (-700kcal, controlled intake)
exercise group with no diet control

both energy deficient groups showed a significant amount of weight loss
NB. artifical situation

all 3 groups showed reduction in visceral fat so still prognostic improvement

Question 21

Explain the findings of the meta analysis carried out by Miller et al 1997

Answer 21

compared trials of diet alone vs exercise alone vs diet + exercise

diet alone saw the greatest weight loss, but weight loss was significantly greater than fat loss so loss of muscle mass

weight loss with exercise was less but was all fat mass

adding exercise to severe diet restriction gave no extra benefit bc already has sufficient energy deficit

Question 22

why does a loss of muscle mass potentially lead to regain of weight after weight loss

Answer 22

loss of muscle mass = reduced RMR

Question 23

what did the study by Anderson et al 1999 demonstrate

Answer 23

there was better maintainence of weight loss in people who underwent lifestyle PA programme than structured PA programme

Question 24

what did the study by Jackicic et al 2008 demonstrate

Answer 24

greater leisure time PA following an exercise trial resulted in better weight loss maintenance

Very little regain in people completing >200 mins/week

Question 25

what are the ACSM guidelines for combining diet and PA

Answer 25

PA will increase weight loss if diet restriction is modest

PA will give no further benefit if diet restriction is severe

Question 26

what is the ACSM guidance for PA for weight maintenance

Answer 26

some studies support 200-300 min/wk to prevent regain

certainly more is better

Question 27

Jeffrey et al 2003

Answer 27

1000kcal/ wk vs 2500

No difference in weight loss at 6 months

But at 12 and 18 th 2500 group had significantly lower weight indicating better maintainence

Question 28

Who published evidence that lower BMI was associated with more activity and what did they show

Answer 28

Kavouras et al 2007

Bmi of people doing 30 mins 5x week was significantly lower than those who were more sedentary

Question 29

How much PA did schoeller et al 1997 say was needed for maintenance and how was this decided on

Answer 29

Double labelled water to determine energy expenditure in women who had lost average of 23kgs

Compared gainers to maintainers

Regression analysis to find that 80 mins/day of moderate intensity or 35 mins/day of intense activity needed to prevent regain