Recent interest in the role of the gut microbiome as well as the alterations in gut physiology that happens with bariatric surgery, have prompted an increasing interest in the biology of bile acids and how they relate to metabolism.
As I distinctly recall from my medical textbooks, the biology of bile acid production and disposition (let alone its many functions within the gut and in the circulation) are anything but simple.
This is why much about how bile acid physiology, especially in relationship to glucose metabolism and obesity remains unclear.
Now, a study by Rebecca Heuseler and colleagues, published in the Journal of Clinical Endocrinology and Metabolism, points to some differences in bile acid production and physiology in individuals with obesity.
In a series of studies, fluctuations in bile acid levels ere measured in 11 nonobese and 32 obese subjects; Bile acid transporter expression in liver specimens were measured in 42 individuals and in specimens of duodenum, jejunum, ileum, colon, and pancreas from 9 individuals.
Measurements were conducted after overnight fasting, during a hyperinsulinemic-euglycemic clamp, or a mixed meal tolerance test.
Markers of bile acid synthesis were twofold higher in subjects with obese subjects and inversely correlated with insulin sensitivity.
While insulin infusion (during the euglycemic clamp) acutely reduced serum bile acids in nonobese subjects, but this effect was blunted in obese subjects.
Subjects with a higher BMI also experiences a blunted rise in serum serum bile acids following a meal compared to non-obese subjects.
What all of this means is largely unclear but as the authors note,
“The findings reveal new pathophysiological aspects of bile acid action in obesity that may lend themselves to therapeutic targeting in metabolic disease.”
Perhaps this is a space to watch.
The ergonomics of standard QUERTY keyboards are bad enough for people of regular size – for larger people, the strain on the upper body is even worse resulting in significant upper-body muskuloskeletal discomfort and even injury.
Now a study by Matthew Smith and colleagues from the University of Georgia, published in Applied Ergonomics provides good evidence for the value of providing people with obesity ergonomically improved open-angle keyboards.
The researchers studied the use of these key boards in 22 office workers with overweight or obesity and found a significant decrease in lower back discomfort with no changes in overall typing performance.
The specific open-angle keyboards used in this study,
“…allows for up to 30° of angle in the keyboard as well as 30° of vertical inclination. The vertical inclination is referred to as a “tent” effect. These adjustments allow the user flexibility in the three-dimensional adjustment of the keyboard to allow for optimal hand placement while typing. These movement capabilities are intended to allow the users to make angular adjustments to the keyboard to minimize wrist supination and both radial and ulnar deviation, all of which are key factors in development of distal upper extremity musculoskeletal diseases.”
From this study the authors conclude that such relatively low-cost interventions can be introduced into the workforce to benefit workers without reducing short-term worker productivity.
Smith ML, Pickens AW, Ahn S, Ory MG, DeJoy DM, Young K, Bishop G, & Congleton JJ (2014). Typing performance and body discomfort among overweight and obese office workers: A pilot study of keyboard modification. Applied ergonomics PMID: 25082778
This is exactly what Anita Kozyrskyj and colleagues from the University of Alberta, Edmonton, Canada, explored in a paper now published in the International Journal of Obesity.
For their study they linked rovincial healthcare records to clinical and survey data from a Canadian longitudinal birth cohort study, whereby antibiotic exposure during the first year of life was documented from prescription records.
Overweight and central adiposity were determined from anthropometric measurements at ages 9 (n=616) and 12 (n=431) years.
According to this analysis, infants receiving antibiotics in the first year of life were about twice as likely to be overweight later in childhood compared to those who were unexposed.
However, after adjustment for birth weight, breastfeeding, maternal overweight and other potential confounders, this association persisted in boys but not in girls. The reason for this discrepancy is not clear.
Although these findings are in line with the notion that early use of antibiotics may predispose to obesity, it is important to not that these type of studies cannot prove causality.
It may well be that other non-measured factors could explain this association (e.g. overprotective or lower SES parents may be more likely to use antibiotics in their infants – both factors are independently associated with higher rates of obesity).
Nevertheless, given the rather high rates of antibiotic exposure in infants it appears that this may well be a promising area for further research not just in the context of obesity but also for many of the other conditions that are now believed to be influenced by intestinal flora.
Azad MB, Bridgman SL, Becker AB, & Kozyrskyj AL (2014). Infant antibiotic exposure and the development of childhood overweight and central adiposity. International journal of obesity (2005) PMID: 25012772
The same is apparently true for humans – while moving to higher altitudes may not make your shorter, it certainly appears to reduce your body fat and perhaps risk of obesity.
Indeed, there is ample evidence from both animal and human studies demonstrating that hypobaric hypoxia (lower oxygen levels combined with lower athmospheric pressure) may have a profound affect on body composition.
Now, a large epidemiological study by Jameson Voss and colleagues, published in PLOS|One provides strong evidence to support this hypothesis.
The researchers looked at all outpatient medical encounters for overweight active component enlisted service members in the U.S. Army or Air Force from January 2006 to December 2012 stationed in the United States and compared obesity related ICD-9 codes between those stationed at high altitudes (>1.96 kilometers above sea level) with those at low altitudes (<0.98 kilometers).
It turns out that service members stationed at higher altitudes were about 40% less likely to become obese than those stationed at lower altitudes.
Although one must always be careful to infer causality from epidemiological evidence, these findings are certainly in line with the experimental evidence on hypobaric hypoxia.
In light of these findings, I can already see the next opportunity for commercial weight loss – hypobaric hypoxic chambers at your local tan studio.
Voss JD, Allison DB, Webber BJ, Otto JL, & Clark LL (2014). Lower Obesity Rate during Residence at High Altitude among a Military Population with Frequent Migration: A Quasi Experimental Model for Investigating Spatial Causation. PloS one, 9 (4) PMID: 24740173
This question was now addressed by Tiberio and colleagues in a paper published in JAMA Pediatrics.
The researchers examined longitudinal data from a community sample in the US Pacific Northwest that indluced 112 mothers, 103 fathers and their 213 kids aged five to nine years old.
The data included what parents reported on their general monitoring of their children (whereabouts and activities), specific monitoring of child media exposure, children’s participation in sports and recreational activities, children’s media time (hours per week), household annual income, and educational level as well as parental BMI was recorded.
It turns out that maternal (but not paternal) reports of monitoring their kid’s media exposure was associated with lower BMI z scores at age seven as well as less weight gain between five and seven years of age.
These findings remained significant even after adjustment for several other variables including total media time as well as sports and recreational activities.
From these findings, the authors conclude that,
“Parental behaviors related to children’s media consumption may have long-term effects on children’s BMI in middle childhood.“
And that these finding,
“…underscore the importance of targeting parental media monitoring in efforts to prevent childhood obesity.”
I would not go quite that far for several reasons.
Firstly, associations do not prove causation. In addition, we don’t know much about other aspects of parenting style from this study that may well also have impacted body weight.
Thus, we could well speculate that moms who monitor their kid’s media consumption may also be more adamant about bed times, healthy eating, or even just spending more time talking to or listening to their kids – all of which may well have positive effects on their kid’s weight.
This is why simply getting parents to be stricter about monitoring their kid’s media consumption may not result in better weights at all.
As always, I find it disconcerting when epidemiological data is used to predict what may or may not happen when interventions target a proposed “cause”.
Nevertheless, for anyone interested in this topic, the following event may be of interest:
On May 1, 2014 the Alberta Teachers’ Association, in partnership with the Alberta Centre for Child, Family and Community Research, is pleased to invite Dr. Michael Rich and Dr. Valerie Steeves to Edmonton for a discussion on how technology is impacting children, youth and society. This is a continuation of our series of evening public lectures with world renowned and distinguished speakers that has included Sir Ken Robinson, Sherry Turkle, Yong Zhao, Jean Twenge, and Carl Honore.
Dr. Valerie Steeves, Associate Professor, University of Ottawa, and principal investigator of the largest Canadian research study on children & teens’ online habits.
Young Canadians in a Wired World (2013) – Explore the highlights of Dr. Steeves’ pioneering Canadian research on children & teens’ online habits.
Dr. Michael Rich, Associate Professor of Pediatrics at Harvard Medical School and Associate Professor of Society, Human Development, and Health at Harvard School of Public Health, Boston, United States.
Ø Centre on Media and Child Health – Explore Dr. Rich’s extensive work on behalf of Children’s Hospital Boston, Harvard Medical School and the Harvard School of Public Health:
Ø CBC national panel discussion on Youth and Technology (February 2014):
There will also be a public lecture on Thursday evening May 1, 2014 entitled “Connected or Disconnected? Technology and Canadian Youth”.
Who: Dr. Michael Rich (Harvard University) and Dr. Valerie Steeves (University of Ottawa)
When: Thursday Evening, May 1, 2014
Where: Barnett House, Alberta Teachers’ Association, 11010 – 142 street NW Edmonton, Alberta
•6:00 pm Registration and reception (hors d’oeuvre and no host bar)
•7:00 pm to 9:30 pm Public lectures and discussions
Order Tickets ($10) Online at http://www.event-wizard.com/
Tiberio SS, Kerr DC, Capaldi DM, Pears KC, Kim HK, & Nowicka P (2014). Parental Monitoring of Children’s Media Consumption: The Long-term Influences on Body Mass Index in Children. JAMA pediatrics PMID: 24638968