Dr. Sharma's Obesity Notes

Prof. Bente Klarlund Pedersen, University of Copenhagen

This week, I am attending the 20th European Congress on Obesity in Liverpool.

The opening plenary lecture this morning was presented by Bente Pedersen from the University of Copenhagen, who reviewed her work demonstrating that the profound positive effects of exercise on metabolism, inflammation, mood and cognitive function are mediated by 100s of proteins secreted from skeletal muscle cells in response to muscle contraction.

These molecules are now referred to as “myokines” and have been shown to exert either autocrine, paracrine or endocrine effects on other organs like adipose tissue, liver, pancreas, bones and brain..

This exciting area of research is nicely summarized in a recent paper by Bente Pedersen and Mark Febbraio published in Nature Endocrine Reviews.

For example, exercise-induced increases in myocellular production of BDNF and IL-6 can increase AMPK-mediated fat oxidation, whereby IL-6 appears to have systemic effects on the liver, adipose tissue and the immune system and even mediates crosstalk between intestinal L cells and pancreatic islets.

Other myokines (e.g. the osteogenic factors IGF-1 and FGF-2; FSTL-1) can improve the endothelial function of the vascular system.

More recently, the myokine irisin, has been shown to promote “browning” of adipose tissue.

Other lines of research suggest that myokines can influence the growth of cancer cells as well as modulate immune function, bone development and pancreatic B-cells.

Current research using proteomic techniques will likely provide further insights into the hundreds of molecules secreted from skeletal muscle in response to physical activity and explain how these myokines mediate the wide-ranging beneficial effects of exercise and the detrimental effects of sedentariness on many chronic diseases.

AMS

Liverpool, UK

You can follow live tweets from the conference at #ECO2013

One of the more persistent “myths” about obesity is that overweight and obese kids are big largely because of their reduced levels of physical activity.

As regular readers may recall, this was not borne out by previous surveys on physical activity, where the relationship between physical activity and body size have been rather inconsistent.

Now a paper by Vorwerg and colleagues from the University of Leipzig, Germany, published in PLoS One, again fails to find a significant relationship between physical activity levels and body weight in German pre-schoolers.

Thus, based on measurements of physical activity using accelerometers, boys generally clocked about an extra hour of vigorously activity per week compared to girls and overall activity levels were significantly lover on weekends than on weekdays.

However, there was no relationship between body weight and levels of physical activity or levels of daily media consumption.

Rather, both body weight and media consumption were inversely associated with decreasing socioeconomic class, which in fact, turned out to be the only variable that had an ‘independent’ impact on body weight.

Thus, the authors conclude that weight status of preschoolers is considerably influenced by socioeconomic factors, but not by physical activity levels.

These findings certainly do not argue against increasing physical activity levels in all pre-schoolers – this is sure to have many health benefits – just perhaps not on body weight.

Will the kids get fitter? Yes! Less fat? Probably not!

AMS
Edmonton, Alberta

Vorwerg Y, Petroff D, Kiess W, & Blüher S (2013). Physical Activity in 3-6 Year Old Children Measured by SenseWear Pro®: Direct Accelerometry in the Course of the Week and Relation to Weight Status, Media Consumption, and Socioeconomic Factors. PloS one, 8 (4) PMID: 23573273

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This weekend, at my presentation in Grande Prairie, I told the packed audience that trying to increase your levels of physical activity (beyond the little that is needed to be moderately fit) may be counterproductive, especially if you are carrying around a significant amount of weight.

Now, a study by Gary Hunter and colleagues from the University of Birmingham, Alabama, published in the Medicine and Science in Sports and Exercise, shows that in older women, working out nearly every day actually reduces total energy expenditure, while providing virtually no additional metabolic benefit.

The researchers randomly assigned 72 women (60-74 years old) to 16 weeks of: 1 day/week of aerobic and 1 day/week of resistance (1+1); 2 days/week of aerobic and 2 days/week resistance (2+2); or 3 days/week aerobic and 3 days/week resistance (3+3). (Aerobic training consisted of 40 minutes of aerobic exercise at 80% maximum heart rate and resistance training consisted of 2 sets of 10 repetitions for 10 different exercises at 80% of one repetition maximum.)

Wile all groups (equally!) increased fat free mass, strength and aerobic fitness, both total energy expenditure (TEE) and activity energy expenditure (AEE) increased with the 2+2 group but not with the other two groups.

As for non-exercise AEE (NEAT), while it increased significantly in the 2+2 group (+200 kcal/day) and showed a trend for an increase in the 1+1 (+68 kcal/day) group, it significantly decreased(!) in the 3+3 group (-150 kcal/day).

Thus, the authors conclude that almost daily 3+3 training may in fact have less beneficial effects on energy balance than 1+1 and 2+2 training.

Assuming that the same holds true for younger individuals (and both men and women), this may mean that getting our patients to exercise just 4 times a week (or perhaps even just twice), may not only be enough but in fact better than dragging themselves to the gym everyday.

In the end, however, I stand by my conviction that the main role of including regular physical activity into your weight management program is to ruin your appetite rather than to burn calories.

AMS
Edmonton, AB

Hunter GR, Bickel CS, Fisher G, Neumeier W, & McCarthy J (2013). Combined Aerobic/Strength Training and Energy Expenditure in Older Women. Medicine and science in sports and exercise PMID: 23377831

Following yesterday’s Obesity Fact #3 (exercise is good for you even if it doesn’t help you lose weight), Obesity Fact #4 from the New England Journal of Medicine paper, states that,

“Physical activity or exercise in a sufficient dose aids in long-term weight maintenance.”

This is a pretty well-established fact, however, the authors hasten to point out that the key term in this “Fact” is the term “sufficient dose”.

Thus, the authors note that,

“Physical-activity programs are important, especially for children, but for physical activity to affect weight, there must be a substantial quantity of movement, not mere participation.”

Indeed, recent studies have questioned whether in fact, the amount of physical activity that is achievable in school phys-ed programs (for example) would provide a sufficient dose to prevent weight gain (let alone maintenance of weight loss).

Thus, this “Fact” reflects the consistent body of knowledge that exercise as a way to control your weight, be it to prevent weight gain, lose weight, or prevent weight regain, requires a substantial dose of activity – more than is perhaps necessary to simply maintain good health (see Obesity Fact #3).

As I have said before, exercise is perhaps best seen as part of energy-in rather than energy-out and the right dose of exercise to help you control your weight is just the amount that it takes to RUIN your appetite. For some people that may well be the benefit you get from walking your dog.

AMS
Edmonton, AB

There is certainly no arguing with obesity fact #3 from the New England Journal of Medicine paper:

“Regardless of body weight or weight loss, an increased level of exercise increases health”

There are indeed countless studies showing how even moderately increasing physical activity can improve glucose metabolism, increase healthy HDL cholesterol, improve cardio-respiratory fitness, improve mood and general well-being, reduces stress levels, improves sleep and even helps ward off some cancers.

However, these studies also show that for most people, losing weight is not one of the benefits of being more active (after all it’s called “working up an appetite” for a reason!).

Thus, while exercise is not the panacea for weight loss (or even preventing weight gain), it is certainly the panacea for good health.

Fortunately for those who may not happen to be the biggest activity enthusiasts, even very moderately increasing activity levels for a few minutes a day can have significant benefits. Indeed, when it comes to the health benefits of exercise – less, done regularly, is often more (especially if you are at a higher weight).

Remember, if you can lift 300 pounds out of that chair and carry them across the room – you’re already an athlete in my books.

AMS
Edmonton, AB