Does Intentional Weight Loss Reduce Mortality?
Given that virtually every risk-factor guideline (from hypertension to diabetes) recommends “weight-loss” as “first-line” treatment, to many this may seem a rather stupid question, but in reality, there is in fact almost no high-qulaity evidence to show that intentional (non-surgical) weight loss actually reduces mortality. This may well be simply because randomised controlled studies on intentional weight loss have either never been long enough, big enough, or able to sustain large enough differences in body weight between the interventions arms. Nevertheless, now a meta-analysis by Stephen Kritchevsky and colleagues from the Wake Forest School of Medicine, published in PLOS one, suggests that being randomised to the intervention arm in a weight-loss study may reduce mortality by 15%. The researchers identified 15 randomised controlled trials of behavioural interventions for weight loss of at least 18 months duration, of which 12 reported at least one death in either of the intervention arms. These studies included 17,186 participants (53% female, mean age 52 years, mean BMI range 30–46 kg/m2 ) with follow-up times ranging from 18 months to 12.6 years (mean: 27 months), and an average weight loss of 5.5±4.0 kg. Based on a total of 264 deaths in weight loss groups compared to 310 in non-weight loss groups, the authors calculated a 15% lower all-cause mortality risk (RR = 0.85; 95% CI: 0.73–1.00) in the weight-loss group. Thus, the authors conclude that being randomized to the weight-loss arm in a behavioural weight-loss study may indeed reduce mortality risk. However, as readers may realise, this study certainly does not “prove” that it is the actual weight loss that mediates these effects. After all, to achieve and sustain weight-loss through behavioural interventions, participants would have had to change their diet and activity levels to a greater extent that those in the control group. Thus it is very possible that the difference in mortality between the groups could well have been due to changes in health behaviours rather than due to the actual weight loss. Nevertheless, the findings are reassuring in that they at least do not show an increase in mortality, something that people have feared may happen with intentional weight loss, especially in older individuals. I guess the most we can conclude from this study is that being lucky enough to be randomised into the “weight-loss arm” of a behavioural weight-loss RCT may just help reduce your mortality risk. @DrSharma Edmonton, AB
Adverse Metabolic Effects of Exercise?
Warning – this is not an April Fool’s post! Rather, it is a follow up to yesterday’s post warning that even “lifestyle” or behavioural interventions can have adverse effects – at least for some people. Point in case, is this paper by Claude Bouchard and colleagues, published in PLOS one back in 2008, clearly documenting clinically significant harmful metabolic effects of exercise in some individuals (about 1 in 10). I would probably have disregarded this paper, except for the fact that the authors include a who-is-who of exercise experts, Steven Blair, Timothy Church, Nathan Jenkins, just to name a few. These are all enthusiastic supporters of increasing physical activity with rock-solid expertise in exercise physiology. Their findings are based on completers from six exercise studies involving a total of 1,687 men and women. Although metabolic parameters in general improved (as expected) in most participants, 8.4% had an adverse change in fasting insulin, 12.2% has a clinically significant increase in resting systolic blood pressure, 10.4% had a relevant increase in fasting triglycerides, and 13.3% had a reduction in HDL-Cholesterol. About 7% of participants experienced adverse responses in two or more risk factors. While the authors note that the explanation for these findings remain unclear, “…the adverse response traits are not explained by prior health status of subjects, age, amount of exercise imposed by the program, or lack of improvement in cardiorespiratory fitness. No evidence could be found for the hypothesis that adverse responses were the result of drug-exercise interactions.” Which brings me back to yesterday’s post, that even the best meant behavioural recommendation (in this case “move more”) can carry risks for some individuals and may require personalised and ongoing monitoring. Funnily enough, I would imagine that if you packed exercise into a pill with these types of “adverse effects”, I wonder if the FDA would actually let you sell it. Incidentally, Claude Bouchard will be one of the key note speakers at the upcoming 4th Canadian Obesity Summit in Toronto, April 28-May 2. I’m sure he will be presenting some of these data and the fascinating genetic studies that have since been done on this issue. @DrSharma Edmonton, AB Hat tip to Morgan Downey for reminding me of this study. To preregister for the Canadian Obesity Summit click here
All Behavioural Interventions Carry Risks
Following the recent release of the Canadian Task Force on Preventive Health Care guidelines for prevention and management of adult obesity in primary care, the Task Force yesterday issued guidelines on the prevention and management of childhood obesity in the Canadian Medical Association Journal (CMAJ). Key recommendations include: For children and youth of all ages the Task Force recommends growth monitoring at appropriate primary care visits using the World Health Organization Growth Charts for Canada. For children and youth who are overweight or obese, the Task Force recommends that primary health care practitioners offer or refer to formal, structured behavioural interventions aimed at weight loss. For children who are overweight or obese, the Task Force recommends that primary health care practitioners not routinely offer Orlistat or refer to surgical interventions aimed at weight loss. The lack of enthusiasm for the prevention of childhood obesity is perhaps understandable as the authors note that, “The quality of evidence for obesity prevention in primary care settings is weak, with interventions showing only modest benefits to BMI in studies of mixed-weight populations, with no evidence of long-term effectiveness.” leading the Task Force to the following statement, “We recommend that primary care practitioners not routinely offer structured interventions aimed at preventing overweight and obesity in healthy-weight children and youth aged 17 years and younger. (Weak recommendation; very low-quality evidence)” Be that as it may, the Task Force does recommend structured behavioural interventions for kids who already carry excess weight based on the finding that, “Behavioural interventions have shown short-term effectiveness in reducing BMI in overweight or obese children and youth, and are the preferred option, because the benefit-to-harm ratio appears more favourable than for pharmacologic interventions.” What caught my eye however, was the statement in the accompanying press release which says that, “Unlike pharmacological treatments that can have adverse effects, such as gastrointestinal problems, behavioural interventions carry no identifiable risks.” (emphasis mine) While I would certainly not argue for the routine use of orlistat (the only currently available prescription drug for obesity in Canada) in children (or anyone else), I do take exception to the notion that behavioural interventions carry no identifiable risks – they very much do. As readers may be well aware, a large proportion of the adverse effects of medications is attributable to the wrong use of these medications – problems often occur when they are taken for the wrong indication, at the wrong dose (too high or… Read More »
Exercise Reduces Cravings For Sugar?
I have long postulated that the benefits of exercise in weight management have little to do with burning calories. Rather, I am pretty sure that when people lose weight with exercise, they do so because of the impact that exercise may have on their food intake (I call it exercising to ruin your appetite!). Thus, I am happy to acknowledge my affirmation bias in paosting about the recent study by Larissa Ledochowski and colleagues from the University of Innsbruck, Austria, published in PLOS One on the outcome of a randomised controlled trial of brisk walking on cravings for sugary snacks. The study was conducted in 47 overweight volunteers who reported habitually consuming a fair share of sugary snacks. Following 3 days of “chocolate abstinence” subjects were randomised (using a within-subject design) to a 15-min brisk walk or passive control. On each occasion, subjects were then stressed using the Stroop color–word interference task after which they reported their urges for sugary snacks using the State Food Craving Questionnaire [FCQ-S] adapted for sugary snacks. Compared to the control situation, brisk walking resulted in a significant and relevant reduction in the urge for sugary snacks and attenuated the increase in sugar-cravings under trigger conditions (stress). Although the authors are careful about not over-interpreting their findings from this acute study (that did not actually measure sugary-snack intake), they do make the following speculation regarding clinical relevance, “This study adds to the increasing evidence that physical activity can somehow help to regulate the urge to consume snack food. It may be easy for overweight people to fit in short bouts of low-moderate intensity physical activity, instead of being sedentary, to elevate affective activation and valence and reduce high energy food cravings which may be triggered by stress and the presence of snack foods.” While I am certain that more intense exercise may well trigger a hunger response, it appears that even a short bout of brisk walking may help dispel those cravings for sugary snacks (let me know if you have experienced this). @DrSharma Edmonton, AB
Patchy Progress on Obesity Prevention – Time To Expand The Food and Activity Paradigm?
In last week’s 2015 Lancet series on obesity, the majority of papers focus on policy interventions to address obesity. It suggests that a reframing of the obesity discussion, that avoids dichotomies (like nature vs. nurture debates) may provide a path forward – both in prevention and management. The policy framework presented by Christina Roberto and colleagues in The Lancet, is based on the NOURISHING framework, proposed by the World Cancer Research Fund International to categorise and describe these actions. Together, the actions in this framework address the food environment (e.g. food availability, taxation, restrictions on advertising, etc.), food systems (e.g. incentives and subsidies for production of healthier foods) and individual behaviour change (e.g through education and counselling). This “food-centric” view of obesity is complemented by recognising that physical activity, much of which is dictated by the built environment and captivity of the population in largely sedentary jobs, also has a role to play. On a positive note, the Christina and colleagues suggest that there may be reasons for careful optimism – apparently 89% of governments now report having units dedicated to the reduction of non-communicable diseases (including obesity), although the size and capacity of many of these units is unknown. On the other hand, despite an increasing number of such efforts over the past decades, no country has yet reversed its epidemice (albeit there is a flattening of obesity growth rates in the lower BMI ranges in some developed countries – with continuing rise in more severe obesity). Despite the potential role of government policies in reducing non-communicable diseases (including obesity) by “nudging” populations towards healthier diets and more physical activity, the authors also note that, “…the reality is that many policy efforts have little support from voters and intended programme participants, and although the passage of policies is crucial, there is also a need to mobilise policy action from the bottom up.” Indeed, there is growing list of examples, where government policies to promote healthy eating have had to be reversed due to lack of acceptance by the public or were simply circumvented by industry and consumers. Nevertheless, there is no doubt that policies in some form or fashion may well be required to improve population health – just how intrusive, costly and effective such measures will prove to be remains to be seen. All of this may change little for people who already have the problem. As the article explains,… Read More »
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