Association does not imply causality yet my money says that this morning (I'm writing this yesterday afternoon) the media reports will be awash with the message that rising Canadian obesity rates may well be a consequence of declining Canadian levels of fitness (as evidenced from yesterday's publication of the Canadian Health Measures Survey).
Personally I would argue that if we're looking for causality it's far more likely that obesity has impacted on fitness rather than the other way around given that fitness doesn't burn nearly as many calories as would be fair.
As an example, here's a video from youtube (email subscribers need to head to the blog to view the video) pitting the treadmill vs. a pizza where the participants aim to illustrate why it is, "you can't out train a bad diet".
Ultimately I believe the evidence strongly suggests it has been the world's rising caloric intake that takes the lion's share of responsibility for fueling the global obesity epidemic, not declining fitness.
So looking at the flip side, could obesity impact on fitness levels? Of course. It's more difficult to exercise with more weight, some folks may be embarrassed to exercise due to their weight, while others may have developed co-morbidities that have impacted on their ability or desire to exercise. Less exercise due to excess weight would of course lead to declining levels of physical fitness.
Or maybe fitness and fatness aren't strongly related at all in either direction. The Canadian survey that's reporting declining fitness notes the decline has occurred since 1981. You know what else has happened since 1981? Cable TV, the Internet, XBOXes and instant messaging have all happened - 4 great reasons as to why fitness may be declining and if my assertion that fitness doesn't burn enough calories to dramatically impact on rising rates of obesity is correct then perhaps as far as a discussion surrounding obesity goes, declining physical fitness is more of a red herring having occurred as a consequence of non-obesity related modern age sloth.
Here's my concern. Fitness as a determinant of health is likely second in importance only to diet. My worry is that when personal or societal interventions to improve fitness as a means to combat obesity ultimately disappoint, that people will abandon fitness having forgotten or ignored the importance of fitness for fitness' own sake.
Posts
If you experienced lately a good aerobic workout like swimming or jogging (not talking about easy walk), you will probably not feel particularly hungry during the next 45 min. If instead to exercise you do nothing, hunger come up quite fast, especially during lunch time. Forces that conditionn behavior is all matter of energy balance regulation in the brain and it is much more complex Yoni than calories intake and calories spent by a mechanical device you show today on You Tube.
ReplyDeletePaul, I realize your belief is that physical fitness is a reasonable answer to the obesity epidemic and certainly we're all entitled to our opinions.
ReplyDeleteThe point of the youtube video is to illustrate the fact that exercise does not burn nearly enough calories.
More importantly than youtube videos are papers the likes of those by Swinburn and Westerterp which posit that weight gain in society is not about declining activity levels but rather about increasing intake levels.
No doubt that shorter duration bouts of exercise can impact on satiety, but in my mind no doubt that obesity has more to do with intake.
As I noted in my blog post - I believe the constant linkage of obesity rates to physical activity will actually serve to hamper efforts to increase physical activity in society as even were those efforts successful, without explicit guidance on energy-intake, I don't think they'll affect weight and consequently will be more likely to be abandoned when weight doesn't change.
It's true that obese people are less active than average, but it is also true that fit and very active people are also leaner compared to average population. I plays on each side for a double effect
ReplyDeleteYoni, I am agree with you that obesity epidemic is MORE due to food intake than to physical activity like recent reviews confirmed. From a strict caloric intake-expenditure point of view, food intake restriction accounts for around 75% of weight loss on average. So, yes diet is the most important aspect of weight loss, but not all.
ReplyDeleteMy POINT is about comments like yours where you seem to dismiss totally the impact and benefits of physical activity into weight loss or weight gain prevention.
A 1kg weight gain over 1 month represents an positive balance of 250 calories, which is due to overintake of foods, especially for someone who is sedentary (50% of the population!) This 250 calories can be spend by a brisk walk of 45 min.
True Paul, but as we discussed on Twitter, I'm not convinced it's a realistic expectation that Canadians will choose to find that time to exercise.
ReplyDeleteThat doesn't mean the exercise wouldn't benefit them, nor does it mean it wouldn't help with maintenance of weight (as indeed it's been shown to do), just that given the dismal failure of efforts to get people to exercise more, perhaps we should be starting to focus more on interventions aimed at changing the environment to help people eat less.
I know I'm a broken record but I truly believe promoting fitness as a means to combat obesity would analagous to advsing a student studying for a final exam where 75% of the material was from the first semester and 25% from the second semester to place more emphasis on the second semester's materials.
The same day Statistics Canada released the results of the Canadian Health Measures Survey http://www.statcan.gc.ca/bsolc/olc-cel/olc-cel?catno=82-623-X&chropg=1&lang=eng and Body composition of Canadian adults 2007 to 2009. http://www.statcan.gc.ca/pub/82-625-x/2010001/article/11091-eng.htm
ReplyDeleteCan you explain the prevalence of elderly? Thought that BMI does not work for seniors? However, I confess that I am in shock of percentages. Thank you for enlightening my lanterns.
BMI certainly is less accurate for the elderly as the natural course of aging is the conversion of muscle to fat.
ReplyDeleteNot sure if you were wondering why the prevalence in the elderly was lower that the rest of the population. If that was your question I'd speculate it's because folks with significant amounts of weight to lose are more likely to die before they become elderly.
Agree with this. I am sedentary and have NEVER been in shape, but I am not obese or overweight. My BMI is smack in the middle of the healthy range and holding steady. I don't exercise, so it's gotta be my diet. I don't eat junk food or eat at chain restaurants, and most of my meals are homemade, not ready-made.
ReplyDeleteHi Mr, People get fatter and heavier and less active and less fit as they get older; no surprise here, although it is sad because they have more time to take care of themself. between 50 and 65, people have a waist circumference that is 2in higher. since 1981, both age group gained 3in!!! That is amazing. That mean that those who were 45 in 1981 are now almost 5in more waist circumberence 18 y later at 63 y old. Explanation: less fit, less active and get tempted into our society of over-consumption.
ReplyDelete