Obesity and Physical Activity Flashcards
Prevalence of obesity in the UK in 2014
Prediction for obesity in 2050
24% in men
26% in women
60% men
50% women
25% children
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
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
Explain the process of adipose tissue acting as an endocrine organ
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
Explain the link between the FTO gene and genetic predisposition to obesity
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
what are the guidelines for starting people on obesity medication and for offering them bariatric surgery
meds = > 30 or >27+ co-morbidities
surgery = >40 or > 35 + co-morbidities
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
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
Physiologically why do people who were previously obese often regain weight
being obese has altered their physiology
body gives out strong hunger signals
what are the three componants of daily energy expenditure and what are their rough contribtions
RMR = 60-70% TEF = 10% PA = 20% but variable
why is it easier to be in positive energy balance than to be in negative energy balance
Adaptive thermogenesis
when output > input mechanisms within the body are activated which aim to make us reduce the energy deficit
explain the study by Church et al 2011 and its findings
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
explain the study by Lee et al 2010 and its findings
give some limitations of this work
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
what are the ACSM guidelines for PA needed to prevent weight gain
150-250 mins per week will prevent weight gain >3% in most adults
Explain the study by Church et al 2007 and its findings
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
Explain the STRRIDE study by kraus et al 2002 and its findings
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
give possible reasons why exercise intervention trials often fail to see significant levels of weight loss
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
What did King et al 2008 demonstrate and how
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
What are the ACSM recommendations for PA to cause weight loss
< 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
explain the meta analysis by Ross et al 2000 and its findings
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
explain the concept of efficacy and effectivness as demonstrated by the meta analysis carried out by Ross et al
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
explain the RCT carried out by Ross et al 2000 and its findings
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
Explain the findings of the meta analysis carried out by Miller et al 1997
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
why does a loss of muscle mass potentially lead to regain of weight after weight loss
loss of muscle mass = reduced RMR
what did the study by Anderson et al 1999 demonstrate
there was better maintainence of weight loss in people who underwent lifestyle PA programme than structured PA programme
what did the study by Jackicic et al 2008 demonstrate
greater leisure time PA following an exercise trial resulted in better weight loss maintenance
Very little regain in people completing >200 mins/week
what are the ACSM guidelines for combining diet and PA
PA will increase weight loss if diet restriction is modest
PA will give no further benefit if diet restriction is severe
what is the ACSM guidance for PA for weight maintenance
some studies support 200-300 min/wk to prevent regain
certainly more is better
Jeffrey et al 2003
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
Who published evidence that lower BMI was associated with more activity and what did they show
Kavouras et al 2007
Bmi of people doing 30 mins 5x week was significantly lower than those who were more sedentary
How much PA did schoeller et al 1997 say was needed for maintenance and how was this decided on
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
