Tag Archives: Exercise

Childhood Decline in Physical Activity

Previously we have seen evidence from a cohort of children and adolescents in Norfolk that the decline in physical activity among modern young people takes place after childhood and during adolescence.[1] However in the majority of studies, including that which we looked at, the estimates of activity are largely based on reports. Now comes a new paper from Farooq and colleagues using objective measurements based on an accelerometer.[2] This new study shows that the previous conclusion was probably wrong. The study shows that there is a decline in moderate to vigorous physical activity throughout childhood and adolescence. A further interesting finding is that this study, based on objective measurements of activity, did not replicate the prevailing view that energy expenditure declines more rapidly in girls than in boys. This paper has considerable implications for policy. I would like to thank Professor Jeremy Dale for bringing this important paper to my attention.

— Richard Lilford, CLAHRC WM Director

References:

  1. Corder K, van Sluijs EMF, Ekelund U, Jones AP, Griffin SJ. Change in children’s physical activity over 12 months; longitudinal results from the SPEEDY study. Pediatrics. 2010; 126(4): e926-35.
  2. Farooq MA, Parkinson KN, Adamson AJ, et al. Timing of the decline in physical activity in childhood and adolescence: Gateshead Millennium Cohort Study. Br J Sports Med. 2017.

Exercise and Energy Expenditure: Not What You Think?

Each week I burn up to 1,500 kcals in my two hours of intense ‘spinning’. So you might have thought (like me) that I could indulge in 1,500 kcals worth of extra puddings. Well you (like me) would have thought wrong, at least according to careful animal and human studies described by Pontzer in this month’s Scientific American.[1] Apparently, short of being an absolute coach potato or an extreme sportsman like Mark Spitz, the rest of us burn the same number of Calories per day, adjusted for mass, irrespective of how much we exercise. Apparently the body compensates for activity by consuming less Calories at rest. Says Pontzer, “exercise to stay healthy, but restrict Calories to control weight

Richard Lilford, CLAHRC WM Director

Reference:

  1. Pontzer H. The Exercise Paradox. Scientific American. February 2017.

 

How Much Exercise Do You Need?

We know exercise reduces the incidence of cancer, diabetes and cardiovascular disease, but how much is needed? The WHO answer to this question is at least 600 on a standardised measure of total (work-related plus leisure) exercise called Metabolic Equivalent Tasks, or METs. This is the ratio of energy expenditure while performing an activity to expenditure at rest. Running for 75 minutes per week, atop of an otherwise sedentary life, yields the WHO standard of 600 METs. Better than nothing, but not enough according to a massive and sophisticated meta-analysis [1] – 2,000 to 4,000 METs are necessary to achieve material benefit (250 – 500 minutes of running). After this threshold, further gains with yet more exercise are nugatory. So lots of exercise is ideal, but excessive exercise is a fetish that wastes time. I aim to do two hours of ‘spinning’ and 90 minutes of doubles tennis each week. Let’s say spinning has an MET of 10, then I spend 1200 MET minutes spinning. If doubles tennis consumes 3 METs, then I spend 270 MET minutes. So my total METs is 1470 – not quite optimal. This study does not shed light on whether 2,000 METs spent in short bursts is better or worse than the same energy expenditure doing something really tedious, like lengths in a swimming pool. For that we need a study comparing “weekend warriors” with people who take similar amounts of exercise, but spread more evenly over the week.[2] The study was based on answers to questionnaires sent to participants in two huge cohort studies – the Health Survey for England and the Scottish Health Survey. The study replicates a link between exercise and overall mortality, cardiovascular mortality, and cancer mortality. However, the pattern of exercise does not seem to make much difference to the risk reduction.

— Richard Lilford, CLAHRC WM Director

References:

  1. Kyu HH, Bachman VG, Alexander LT, et al. Physical activity and risk of breast cancer, colon cancer, diabetes, ischemic heart disease, and ischemic stroke events: systematic review and dose-response meta-analysis for the Global Burden of Disease Study 2013. BMJ. 2016; 354: i3857.
  2. O’Donovan G, Lee I-M, Hamer M, et al. Association of “Weekend Warrior” and Other Leisure Time Physical Activity Patterns With Risks for All-Cause, Cardiovascular Disease, and Cancer Mortality. JAMA Intern Med. 2017.

Nobel and Lasker Prizes

Many years ago we posted an article on autophagy – the process by which cells reutilise their basic components. We cited research showing that a borderline starvation diet is associated with greater longevity in all species where it has been tried.[1] Intense exercise is also associated with widespread health benefits and prolonged life. Autophagy provides a link between these two sets of observations, since both calorie restriction and exercise induce and accelerate autophagy. News Blog readers will therefore be interested to learn that this year’s Nobel prizes for Medicine and Physiology was awarded for the discovery of the mechanisms for autophagy, originally in yeast, by Prof Yoshinori Ohsumi.

The Lasker award for Basic Medical Research went to the three researchers, one from Oxford, who discovered molecular pathways through which changes in oxygen levels provoke a response in cells. It turns out that mechanisms to sense and respond to ambient oxygen levels are present in all cells, not just those that manufacture erythropoietin. This story is quite complex, and readers are referred to a recent article in JAMA.[2]

— Richard Lilford, CLAHRC WM Director

References:

  1. Colman RJ, Anderson RM, Johnson SC, et al. Caloric restriction delays disease onset and mortality in rhesus monkeys. Science. 2009; 325: 201-4.
  2. Kaelin Jr WG, Ratcliffe PJ, Semenza GL. Pathways for Oxygen Regulation and Homeostasis. The 2016 Albert Lasker Basic Medical Research Award. JAMA. 2016; 316(12): 1252-3.

Is it Better to Cycle or Take the Car in Heavily Polluted Cities?

It is often said that it is better to exercise than remain sedentary, even in heavily polluted environments. These statements are based on modelling studies that draw their data from empirical investigations of the dose response curves for increasing activity and increasing pollution (as measured by particulates in the range 5-200 mg/m3):

058 DC - Cycle or Car in Polluted Cities - Fig1

A recent modelling study [1] finds that the balance of harms to benefits does not become adverse except in the cities at the very highest end of the distribution of pollution levels, i.e. levels seldom seen, even in heavily polluted cities. However, these studies do not consider the other risks of certain activities, such as cycling, which, we think, should be included in such models.

— Richard Lilford, CLAHRC WM Director

Reference:

  1. Tainio M, de Nazelle AJ, Götschi T, et al. Can air pollution negate the health benefits of cycling and walking? Prevent Med. 2016; 87:233-6.

Cost-Effectiveness of Exercise and Diet for Diabetes Prevention

I promised that I would report on the cost-effectiveness studies in the systematic review of exercise and diet therapy for the prevention of diabetes discussed in a previous post.[1]

Most studies end three years after the start of the intervention, while the most substantial potential benefits accrue later. Some studies did not model these longer-term benefits, but most extrapolated over ten years or more. Most used previously published model structures such as the Archimedes model. Incremental Cost-Effectiveness Ratios (ICERs) were calculated in 22 studies, all but two of which showed that the intervention (whether group- or individual-based) was cost-effective at a $50,000 Willingness-to-Pay (WTP) threshold. Two studies (both concerning a group intervention) actually suggested the intervention was cost releasing. Averaged across all studies the ICER was about $13,000 per QALY (quality-adjusted life year). CLAHRC WM is collaborating with CLAHRC East Midlands on a study to prevent later onset diabetes in women who have had gestational diabetes. These models will be useful for the calculation of the incremental cost-utility of our intervention.

— Richard Lilford, CLAHRC WM Director

Reference:

  1. Li R, Qu S, Zhang P, et al. Economic Evaluation of Combined Diet and Physical Activity Promotion Programs to Prevent Type 2 Diabetes Among Persons at Increased Risk: A Systematic Review for the Community Preventative Services Task Force. Ann Intern Med. 2015; 163(6):452-60.

Preventing the Onset of Diabetes: No Case for Nihilism

The Community Prevention Services Taskforce in the US commissioned an evidence review of the effectiveness of programmes to promote exercise and weight loss on prevention of diabetes.[1] The headline message is that programmes targeting both weight loss and exercise are effective at reducing the onset of diabetes by about 40% over a three to six year period. Intensive programmes are more effective than less intensive ones. The diet/exercise programmes also resulted in improvement in blood fats and systolic blood pressure. The literature is extensive – 53 studies in all, and there was no evidence of publication bias on Egger’s test.[2] We will discuss health economic analysis of the intervention in a forthcoming news blog.[3]

— Richard Lilford, CLAHRC WM Director

References

  1. Balk E, Earley A, Raman G, Avendano EA, Pittas AG, Remington PL. Combined Diet and Physical Activity Promotion Programs to Prevent Type 2 Diabetes Among Persons at Increased Risk: A Systematic Review for the Community Preventative Services Task Force. Ann Intern Med. 2015; 163(6): 437-51.
  2. Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ. 1997; 315(7109): 629-34.
  3. Li R, Qu S, Zhang P, et al. Economic evaluation of combined diet and physical activity promotion programs to prevent type 2 diabetes among persons at increased risk: a systematic review for the Community Preventive Services Task Force. Ann Intern Med. 2015; 163: 452-60.

How Much Sugar is too much?

News Blog readers enjoy snippets regarding sugar. Now that fat has been given a (fairly) clean bill of health, it is perhaps fortunate that we have a public enemy to take its place – ‘pure, white and deadly’. Food labelling usually gives details on “added sugar”. However, this is a poor index of risk for the obvious reason that food or drink may have lots of sugar, but very little added sugar. Fruit juice is often packed with sugar, even if it is not added; our ancestors did not have electronic juice makers. So “free sugar” is the index of risk that should be used. It describes all the rapidly absorbable extra-cellular sucrose, both added and intrinsic.

Two recent WHO-sponsored systematic reviews describe the correlation between free sugar and risk.[1] [2] The risk of both dental cavities and obesity rises rapidly when free sugars account for over 10% of daily energy intake, and the ‘safe level’ is under 5%. The CLAHRC WM Director, consolidating this blog with preceding posts,[3] [4] has two big messages:

  1. Strong public health messages and nudges are needed to control sugar intake at the population level. This, not promotion of exercise, will stop obesity.
  2. Once an individual is obese they will not lose appreciable weight without surgery. But their health, like that of all people, can be radically improved by exercise.

— Richard Lilford, CLAHRC WM Director

References:

  1. Moynihan PJ & Kelly SA. Effect on caries of restricting sugars intake: systematic review to inform WHO guidelines. J Dent Res. 2014; 93(1):8-18.
  2. Te Morenga L, Mallard S, Mann J. Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ. 2013; 346: e7492.
  3. Lilford RJ. More, Yes More, on ‘Pure, White and Deadly’. July 3 2015 [Online].
  4. Lilford RJ. More, Yet More, on ‘Pure, White and Deadly’. July 31 2015 [Online].

The EarlyBird Study

Our CLAHRC, like many sibling CLAHRCs, has a primary prevention theme partnering with local authorities. Local authorities are having to deal with increasingly constrained budgets. Dr Ewan Hamlett, adviser to the Birmingham Council, recently drew the CLAHRC WM Director’s attention to the EarlyBird study.

This unique study, based in Southampton, follows a cohort of five year-olds to see what factors are associated with obesity and insulin resistance, and detailed information relating to metabolism is collected from participants. Results are starting to emerge and many are highly policy-relevant.[1]

Some headline, policy-relevant findings include:

  • Provide more school playing fields if you wish, but not because it will increase exercise or tackle obesity – it won’t do either of these things.
  • As with education, don’t wait until school age to tackle the problem – children are programmed to over-eat before they go to school.
  • Obese parents produce obese children, yet they tend to be oblivious to the problem. Follow policies to get parents ‘on-side’.
  • Among children, the mean weight has shot up, but the median has not. A subgroup of children with fat parents is at greatest risk.

— Richard Lilford, CLAHRC WM Director

Reference:

  1. EarlyBird Diabetes Trust. “Key Findings from EarlyBird.” 2015. [Online].

Exercise and Health

Readers of the News Blog will have seen previous articles on exercise and health.[1] [2] It is more dangerous to have diabetes or to smoke than to be a coach potato, but there are many more coach potatoes than people living with diabetes or smokers, so overall, more people lose their lives from inactivity than from either the diabetes or the tobacco. It also turns out that the marginal gains of more exercise decrease as total exercise increases. Totally sedentary people (about 25% of the US population) have by far the highest risk. This is the basis for an interesting review and editorial in the Annals of Internal Medicine, advocating policy focusing on the totally sedentary,[3] [4] as well as a news article in the BMJ.[5]

— Richard Lilford, CLAHRC WM Director

Reference:

  1. Lilford R. Anti-obesity interventions. Dec 12 2014. [Online].
  2. Lilford R. Two provocative papers on diet and health. Dec 12 2014. [Online].
  3. Biswas A, Oh PI, Faulkner GE, Bajaj RR, Silver MA, Mitchell MS, et al. Sedentary time and its association with risk for disease incidence, mortality and hospitalization in adults: a systematic review and meta-analysis. Ann Intern Med. 2015;162; 123-32.
  4. Lynch BM, Owen N. Too much sitting and chronic disease risk: steps to move the science forward. Ann Intern Med. 2015;162: 146-7
  5. Mayor S. Prolonged sitting increases risk of serious illness and death regardless of exercise, study finds. BMJ. 2015; 350: h306.