Stretching The Rubber Band
I remember as a kid having a pair of pyjamas that were held up by an elastic rubber band. It must have been a pretty cheap rubber band, because every few months it would wear out and lose its stretch, so it had to be replaced it with a new band. Unfortunately, this is not what can be said about the rubber band that I used in my recent TEDx talk to demonstrate what happens when you try to lose weight. Unlike the cheap band in my pyjamas, the rubber band I used to represent our physiology trying to gain the weight back, never seems to lose its stretch. No matter how hard or how long we pull, the rubber band keeps wanting to bring our weight back to where we started. Yes, perhaps for some people, eventually the rubber band may relax (these would certainly be the exceptions) or may be the “muscles” that we use to pull on the band just grow stronger, which makes it seem easier to keep up the pull – but for all we know, in most people, this “rubber band” is of pretty good quality and seems to last forever. So, how do we take the tension out of the rubber band ? Well, we do know that people who have bariatric surgery have a much better chance of keeping the weight off in the long-term and we now understand that this has little to do with the “restriction” or the “malabsorbtion” resulting from these procedures but rather from the profound effect that this surgery has on the physiology of weight regain. Thus, we know that many of the hormonal and neurological changes that happen with bariatric surgery, seem to inhibit the body’s ability to defend its weight and perhaps even appears to trick the body into thinking that its weight is higher than it actually is. In other words, bariatric surgery helps maintain long-term weight loss by reducing the tension in the rubber band, thus making it far easier for patients to maintain the “pull”. And that is exactly how we think some of the anti-obesity medications may be working. For example, daily injections of liraglutide, a GLP-1 analogue approved for obesity treatment, appears to decrease the body’s ability to counteract weight loss by reducing hunger and increasing satiety, thus taking some of the tension out of that band. Think of it as sprinkling “magic dust” on that rubber band to reduce the… Read More »
How To Interpret Studies On Screen Time And Eating Behaviour
Much of the research on the contribution of screen time, sedentariness, food consumption and other factors comes from cross-sectional or longitudinal studies, where researchers essentially describe correlations and statistical “effect sizes”. To be at all meaningful, analyses in such studies need to be adjusted for known (or at least likely) confounders (or at least the confounders that happen to available). No matter how you turn and wind the data, such studies by definition cannot prove causality or (even less likely) predict the outcome of actual intervention studies. Nevertheless, such studies can be helpful in generating hypotheses. Thus, for example, I read with interest the recent paper by Lei Shang and colleagues from the University of Laval, Quebec, Canada, published in Preventive Medicine Reports. The researchers looked at cross-sectional data on 630 Canadian children aged 8-10 years with at least one obese biological parent. While the overall median daily screen time was about 2.2 hours, longer screen time was associated with higher intake of energy (74 kcal) and lower intake of vegetables & fruit (- 0.3 serving/1000 kcal). This unhealthy “effect” of screen time on diet appeared even stronger among children with overweight. Thus, there is no doubt that the study shows that, “Screen time is associated with less desirable food choices, particularly in overweight children.” The question of course remains whether or not this relationship is actual causal or in other words, does watching more television lead to an unhealthier diet (I am guessing no one assumes that eating an unhealthier diet leads to more TV watching). Unfortunately, this is not a question that can be answered by this type of research. Nor, is this type of research likely to predict whether or not reducing screen time will get the kids to eat better. Indeed, it doesn’t take a lot of imagination to come up with other explanations for these findings that would not require any assumption of a causal link between eating behaviours and television watching. For one, TV watching could simply be a surrogate measure for parenting style – perhaps parents that let their kids watch a lot of TV are also less concerned about the food they eat. And, for all we know, reducing TV time may (e.g. by cutting the kids off from TV – or cutting the parents off from a convenient babysitter) in the end make the kids eating behaviours even worse. Who knows – that’s… Read More »
Liraglutide Alters Brain Activity Related to Highly Desirable Food Cues
Liraglutide, a GLP-1 analogue now available for the treatment of obesity (as Saxenda) in North America, works by reducing appetite and increasing satiety, thus making it easier to lose weight and keep it off (with continuing treatment). Now, a study by Olivia Farr and colleagues, in a paper published in Diabetologia not only present data showing the presence of GLP-1 receptors in human cortex, hypothalamus and medulla, but also provide functional evidence for altered brain response to food cues. After documenting the presence of GLP-1 receptor in human brains using immunohistochemistry, the researchers conducted a randomised controlled placebo-controlled, double-blind, crossover trial in 18 individuals with type 2 diabetes who were treated with placebo and liraglutide for a total of 17 days each (0.6 mg for 7 days, 1.2 mg for 7 days, and 1.8 mg for 3 days). Using functional MRI neuroimaging studies, the researchers found that liraglutide remarkably decreased activation of the parietal cortex in response to highly desirable (vs less desirable) food images. They also observed decreased activation in the insula and putamen, areas involved in the reward system. Furthermore, using neurocognitive testing, the researchers showed that increased ratings of hunger and appetite correlated with increased brain activation in response to highly desirable food cues while on liraglutide. In contrast, ratings of nausea (a well-known side effect of liraglutide) correlated with decreased brain activation. As the authors note, “Our data point to a central mechanism contributing to, or underlying, the effects of liraglutide on metabolism and weight loss.” These findings no doubt match the reports from my own patients of experiencing less interest in highly palatable foods and finding it much easier to pass up on foods that they would have otherwise found hard to resist. Clearly, as we learn more about brain function in eating behaviour, we are thankfully moving towards treatments that are clearly proving to be far more effective than just telling patients to “simply eat less” (which I have often likened to telling people with depression to “simply cheer up”). @DrSharma Edmonton, Canada Disclaimer: I have received honoraria for speaking and consulting from Novo Nordisk, the maker of liraglutide
Skinny Kids Eat More Candy
A common assumption is that kids with obesity consume more high-caloric foods – which of course includes confectionary items like chocolate and non-chocolate sweets. Now, a study by Constantin Gasser and colleagues from Melbourne, Australia, in a paper published in the American Journal of Clinical Nutrition, present a systematic review and meta-analysis of confectionary consumption and overweight in kids. The researchers identified 19 studies fort their systematic review, 11 of which (∼177,260 participants) were included in the meta-analysis. Overall, odds of excess weight of kids in the highest category of sweets consumption was about 20% less than in the reference category. This inverse association was true for both chocolate and nonchocolate confectioneries. Furthermore, in the longitudinal studies and the randomised controlled trial included in the review, no associations were observed between confectionery consumption and overweight, obesity, or obesity-related outcomes. Thus, based on data from well over 175,000 kids, there appears to be no relationship between sweets consumption and excess weight – if anything, the relationship is the opposite of what one may expect. As so often, when data don’t fit the “accepted” hypothesis, the authors are also quick to point out that these findings could well be explained by reverse causality (overweight kids avoiding sweets) or underreporting by heavier kids (a polite way of saying that heavier kids may be less honest about their candy consumption). On the other hand, it may also well be that regular (non-restrictive) sweet consumption actually does in fact make kids less vulnerable to overeating, simply by ruining their appetite (just as grandma always warned you it would – as in, “No sweets before supper!”). Overall, the findings remind me of a previous study that failed to find any association between sugary pop consumption and body weight in Ontario and PEI kids (if anything skinny kids in PEI drank more pop than those with excess weight). Whatever the true answer may be, these findings certainly do not support the notion that sweet or chocolate consumption is a key factor in childhood obesity. @DrSharma Edmonton, AB
Ideological Conflicts of Interest Worry Me More Than Financial Conflicts
A few weeks ago I was asked to give a plenary talk on the nature of conflicts of interest at the opening session of the American Society of Nutrition meeting in San Diego. As I explained to the audience, while I do not disregard or trivialize the potential conflict of interest that may come from financial interests (e.g. such as holding a patent or industry funding), we need to also be aware of other powerful conflicts that range from a simple desire to advance one’s personal career (e.g. get tenure, publish in a high-impact journal) to ideological conflicts (e.g. as in spinning research findings to support dearly held world-views or hypotheses). Whereas disclosing financial conflicts is relatively straightforward (and now pretty much the norm), disclosing other conflicts is more challenging. Just how devastating ideological conflicts can be to the scientific discourse is perhaps best illustrated by the recent publication by Chritopher Ramsden and colleagues in the British Medical Journal on their analysis of recovered data from the Minnesota Coronary Experiment (MCE). Conducted back in 1968-73, the MCE was not only the largest (n=9570) but also the most rigorously executed randomized controlled dietary trial of cholesterol lowering by replacement of saturated fat with vegetable oil rich in linoleic acid. The MCE, conducted in one nursing home and six mental health hospitals in Minnesota (apparently an accepted practice back then), is the only dietary study to-date to fully rely on postmortem assessment of coronary, aortic, and cerebrovascular atherosclerosis grade and infarct status and the only one to test the clinical effects of increasing linoleic acid in large prespecified subgroups of women and older adults. The trial was initiated by Ancel Keys, a fervent supporter of the idea that atherosclerosis was directly related to dietary saturated fat intake and a champion of replacing dietary fats with vegetable oils rich in linoleic acid. Importantly, this line of thinking was the driver behind the low-fat recommendations that found their way dietary recommendations and ultimately the low-fat craze that characterized much of second half of the last century. Although completed in 1973, the findings from this study were never published – until now, when Ramsden and colleagues not only managed to recover the original data but also to conduct the analyses according to hypotheses prespecified by original investigators. As has been suspected by some for a long time, the results turn out to be devastating for the idea that… Read More »
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