Is Global Warming Contributing to Obesity?

In parallel with the rising obesity rates around the world over the last decades, so too have we seen an environmental trend of global warming.  I never stopped to consider that the two might be related - until now.

A thought provoking paper just published by my Danish colleagues suggests that there may be a link between increasing atmospheric carbon dioxide levels (as observed with global warming) and obesity.  Breathing in air containing higher carbon dioxide (CO2) level causes the pH of the blood to decrease ever so slightly.   The brain is exquisitely sensitive to these small changes, and the activity of neural cells that are involved in appetite regulation are affected.  In addition, these decreases in pH may affect neurons that regulate wakefulness, resulting in less sleep, which is a known risk factor for obesity.

Therefore, they hypothesize that these small pH changes in our blood seen with higher CO2 concentrations in the air could lead to an increase in appetite as well as energy storage, and could therefore be one of the many contributors to the high rates of obesity that we currently see.

My colleagues went on to test this theory in a small study of six participants, and found that study participants consumed 6.1% more calories when exposed to higher CO2 concentrations in the air, compared to ambient air.  It is noted that this difference was not significant in the study, but a study of a larger size is now needed to see if there is a real difference here.

The obesity endemic, therefore, may be one more important item to add to the list of reasons to put a stop to global warming.

Dr Sue Pedersen www.drsue.ca © 2012

drsuetalks@gmail.com 

Follow me on Twitter for daily tips! @drsuepedersen 

Read more...

Does The Composition of Your Diet Affect POUNDS LOST?

The research world has long been trying to figure out whether the protein, carbohydrate, and fat content of a diet matters, or whether it is 'simply' all about the number of calories being taken in, that determines the end effect on weight.  While a large clinical trial suggested that the composition of the diet doesn't matter, there may be certain elements of this trial that make it difficult to draw these conclusions.

In the POUNDS LOST trial, originally published in 2009 in the New England Journal of Medicine, over 800 overweight adults were randomly assigned to diets with different proportions of fat, carbs, and protein.  At the two year follow up, weight lost was similar in all groups, regardless of the diet composition, leading the authors to conclude that the composition of the diet doesn't matter, and that it's all about the calories.

In a follow up to the POUNDS LOST trial, the authors recently published further data suggesting that there was not only no difference in weight between the various diet groups, but no difference in changes in body composition, abdominal fat, or liver fat lost between the groups either.

In an accompanying editorial in the American Journal of Clinical Nutrition, my colleague Arne Astrup and I comment that further analysis of the POUNDS LOST data show that, based on urine excretion of nitrogen, which is a marker of dietary protein intake, there was actually no difference in protein intake between the low and high protein diet groups.  In other words, despite being assigned diets with different protein content, the participants ended up eating the same amount of protein after all.   As such, it is not actually possible to assess the effect of protein content on weight loss success based on this study.

The heart of the problem is that it is very difficult for study participants to adhere to a hard and fast dietary regimen for the duration of a study.  Although people in this study were asked to eat different amounts of protein, they ended up eating much the same.   Much better is to design dietary trials which point participants towards consumption of certain types of foods, without a fixed caloric intake or diet composition assigned.  That way, we can study how different types of foods affect weight via their natural effects on hunger and satiety.  This is a much more practical way to address the obesity epidemic from a research perspective, as it more accurately represents eating patterns in real life!

Dr Sue Pedersen www.drsue.ca © 2012

drsuetalks@gmail.com 

Follow me on Twitter for daily tips! @drsuepedersen  

Read more...

Photos in Lunch Trays Increase Veggie Consumption in Kids

While the focus of healthy eating tableware tends to be on limiting portions of carbs and proteins, a study group out of Minnesota took a different slant with a group of kids by putting photos of vegetables in their lunch trays - and it worked!

The study, recently published in the Journal of the American Medical Association, looked at the consumption of carrots and green beans at a school cafeteria, comparing eating patterns on a day with pictures of carrots and green beans placed in the bottom of the tray, to a day when there were no pictures placed in the tray.   Kids helped themselves on both days to these vegetables as they wished, and were not aware that their selection or eating patterns were being recorded.

They found that the number of kids who selected green beans more than doubled (from 6.3% to 14.8%), and the number who selected carrots more than tripled (from 11.6% to 36.8%).  However, the number of kids choosing these vegetables overall was still low; further, the amount consumed was low, and did not meet government recommendations.

What this study teaches us is that the power of suggestion can have an impact on helping kids make healthier choices, with minimal additional cost above other much more expensive interventions such as structured classroom teaching.  While the classroom teaching is a crucial part of teaching our kids to eat healthy, let's not forget that a picture speaks a thousand words!

Dr Sue Pedersen www.drsue.ca © 2012

drsuetalks@gmail.com 

Follow me on Twitter for daily tips! @drsuepedersen 

Read more...

How You Taste Fat May Be Genetically Determined

As the human genome is being explored in more detail, the genetic contribution to obesity is becoming increasingly recognized.  While we know of at least 45 genes that contribute to obesity, little is understood about how they work.  A new study has discovered a gene that affects how we sense and taste fat in our mouths, and postulates that this gene may be one more mechanism that contributes to the development of obesity in people who are genetically prone.

The study, conducted by MY Pepino and colleagues at Washington University, looked at 21 people with obesity and different variants of a gene called the CD36 gene.  They found that people who had two copies of a certain variant of the CD36 gene had an 8 fold lower threshold for sensation of fat than people who had no copies of this gene variant.  In other words, people with two copies of the gene variant were far more sensitive to the taste of fat than people without this gene variant.

Exactly how these genetic differences affect food intake is not known.  It may be, for example, that people who are less sensitive to the taste of fat need to eat more fat to feel satisfied.   Further study is needed to understand how the difference in sensitivity to the taste of fat may affect food intake and body weight.

What is increasingly clear is that genetics have a powerful role in the risk of obesity, in the context of the toxic enviroment in which we live.

Note: you can read more about the genetics of obesity here.

Dr Sue Pedersen www.drsue.ca © 2012

drsuetalks@gmail.com 

Read more...

Childhood Obesity and Cardiovascular Risk in Adulthood

It is well known that obesity in all age groups is associated with increased cardiovascular risk.  However, for people who struggle with obesity in childhood but become normal weight in adulthood, it has not been clear whether the risk factors accrued in childhood extends to an increased risk in adulthood. A new study suggests that for these people who achieve a normal body weight in adulthood following childhood obesity, several risk factors for cardiovascular disease are no longer elevated, and are similar to the cardiovascular risk factors of people who were never obese.

The study, published yesterday in the New England Journal of Medicine, analyzed data from over 6,000 people in USA, Australia, and Finland, followed for an average of 23 years. They evaluated several cardiovascular risk factors, including cholesterol profiles, blood pressure, presence of diabetes, and thickness of the wall of the carotid artery (which is a marker for cardiovascular disease), and looked at how these risk factors varied depending on whether individuals were overweight or obese in childhood and/or adulthood.

They found that for people who were obese in childhood and adulthood, the risk of having each of these risk factors for heart disease was several fold higher than for people who were normal weight in childhood and in adulthood.

Importantly, they also found that for people who were obese in childhood but normal body weight in adulthood, their risk factors in adulthood were no different than for people who were never obese.

While the ideal management of childhood obesity is prevention on a societal level, the treatment of obesity in childhood is clearly crucial as well.  This study lends strong support to the importance of treating childhood obesity, as improving body weight towards a normal BMI reduces cardiovascular risk.


Dr Sue Pedersen www.drsue.ca © 2011 drsuetalks@gmail.com

Follow me on Twitter for daily tips! @drsuepedersen

Follow me on Facebook: drsue.ca

Read more...

Genetics Influence Response of Body Weight to Gastric Bypass Surgery

Gastric bypass surgery is an increasingly utilized treatment option for severe obesity worldwide.  While this surgery can be very successful to result in substantial and sustained weight loss over the long term, individual results from person to person are highly variable.  A recent study suggests that a person's genetics may be the primary factor responsible for this variation.


The study, just published in the Journal of Endocrinology and Metabolism by Ida Hatoum and colleagues, examined the DNA of 848 patients undergoing gastric bypass surgery at the Massachusetts General Hospital.  Amongst these patients were 13 pairs of first degree relatives, none of whom were living together.  An additional 10 pairs of patients were identified who were living together but not related (thus allowing a comparison of the effect of environment on the efficacy of surgery). The remaining 794 people in the study were randomly paired for a non-genetic, non-environmentally connected comparison group. 

Interestingly, the study found that first degree relatives had a similar response to surgery, with an average of only 9% difference in the excess weight lost between members of each pair.  In contrast, there was a 26% difference in excess weight lost between cohabitating, unrelated individuals, which was no more similar than unrelated randomly paired individuals, who had a 25% difference in excess weight.

These results suggest that genetics have a strong influence on the effect of gastric bypass surgery on body weight.  Interestingly, they also suggest that the home environment does not have an influence on the efficacy of gastric bypass surgery.

We are certainly becoming increasingly aware of the strong genetic influence in obesity.  Dozens of genes which contribute to obesity risk have been identified so far, and this number continues to climb as our knowledge base grows.  It is therefore perhaps unsurprising to learn that genetics play a strong part in the response to bariatric (weight loss) surgery as well.

The current study examines the influence of genetics on the lowest weight reached (called the 'nadir') after gastric bypass.  I would be very interested to know if genetics has an equally strong influence on the risk of weight regain after hitting the nadir weight postoperatively, as there is also quite a substantial variation in weight maintenance vs weight regain in the long run after bariatric surgery.  More study is needed in this area.

Although this study was too small to be able to identify the specific genetic contributors to weight loss success after gastric bypass surgery, larger scale studies could be undertaken to examine the entire human genome to try to identify the relevant genes.  It is likely that there are many genes involved here, and their interactions are likely to be extremely complex.  Discovery of new genetic mechanisms involved in the response to surgery may teach us something not only about surgery but about obesity in general, possibly leading us down the path to other discoveries that will assist us in non-surgical treatment of obesity as well. 

As for people currently contemplating gastric bypass surgery, this study is too small to make definitive conclusions, but if you have a first degree relative (parent, sibling, or child) who has had the surgery, the success they experienced may be predictive of your own.


Dr Sue Pedersen www.drsue.ca © 2011 drsuetalks@gmail.com

Follow me on Twitter for daily tips! @drsuepedersen

Follow me on Facebook: drsue.ca

Read more...

Video Blog - Highlights from American Obesity Society Conference

In this video blog, Dr Sue discusses just a few of the many highlights from this week's Obesity Society meeting in Orlando, Florida.

Some of the highlights include:

1.  A focus on learning more about the genetics of obesity;

2.  Food Reward: Do differences in how we desire, and how we enjoy, food, affect our risk of weight gain?

3.  Lifestyle interventions:  a focus on building environments that are conducive to more exercise and healthy eating

4.  Medications: nothing new currently, but many interesting possibilities on the horizon...

5.  Bariatric surgery: more data on longterm success rates, and novel technologies being studied.

Watch to learn more!

Dr. Sue © 2011   www.drsue.ca     drsuetalks@gmail.com

Follow me on Twitter for more tips! drsuepedersen

Follow me on Facebook: drsue.ca

Read more...