S1W1 Obesity and Energy Balance part 7

Question 1

Evidence of the effects of physical acitvity on BMI?

Answer 1

• study by Van Dyck et al (2015)
• 6,000 individuals from 10 European countries given an accelerometer for a week
• found that doing more moderate to vigorous activity was associated with a lower BMI
• sedentary time was not found to be associated with BMI

Question 2

Evidence for exercise preventing weight gain with age

Answer 2

• study by Hankinson et al (2010)
• individuals tracked over 20 years
• more active = less change in BMI
• suggesting that people who are more active are less likely to put on weight as they age

Question 3

Does physical activity moderate genetic susceptibility?

Answer 3

• study by Wang et al (2017) followed participants over 20 years and put them into genetic risk categories
• People with greater genetic risk tend to put more weight on every year as they age
• But people with greater genetic risk who were more active didn’t put weight on
• therefore showing that high levels of physical activity protect against genetic predisposition

Question 4

What are the ACSM guidelines for exercise to prevent weight gain?

Answer 4

The American College of Sports Medicine guidelines say ‘Physical activity of 150-250 min/week with an equivalent of 1200 to 2000 kcal/week will prevent weight gain greater than 3% in most adults’.

Question 5

Is following the average government guidelines for exercise enough for weight loss?

Answer 5

No
* a study by Church et al (2007) showed that seeting the average government guidelines for overall health of 30 mins x 5 of moderate to vigorous activity does not lead to weight loss
* because the energy expenditure with this volume of exercise is so low it doesn’t impact energy balance in a meaningful way

Question 6

Does exercise lead to weight loss on it’s own?

Answer 6

• only under strictly controlled conditions so strict diet but this isn’t real life

Question 7

Why will there be differences in weight loss between individuals when doing the same volume of exercise?

Answer 7

• compensatory hunger
• compensatory changes in metabolic rate

Question 8

What are the ACSM guidelines for physical activity to generate meaningfull weight loss?

Answer 8

• ‘Physical activity < 150 min/week promotes minimal weight loss; physical activity > 150 min/week results in modest weight loss (2-3kg); physical activity > 225-420 min/week results in 5 to 7.5kg weight loss
• In terms of the guidelines, if you want to generate clinically meaningful weight loss, you need to be doing about an hour of moderate to vigorous physical activity a day

Question 9

Is diet or exercise more effective for weight loss?

Answer 9

• a study by Ross et al (2000) shows diet is more effective than exercise for weight loss

Question 10

Why is dieting usually more effective for weight loss than exercise?

Answer 10

• It takes longer to expend energy than to consume it e.g. takes a lot longer to burn 600 calories with exercise than to eat a 600 calorie muffin
• Energy intake is 100% controllable; expenditure is ~20%

Question 11

What are the ACSM guidelines for physical activity and dietary restrictions for weight loss?

Answer 11

• ‘Physical activity will increase weight loss if dietary restriction is modest but not if diet restriction is severe’
• If someone is eating a very low number of calories, you are already in a large calorie deficit so exercise won’t do much on top of that