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How You Taste Fat May Be Genetically Determined

>> Sunday, January 29, 2012

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 © 2012 

Follow me on Twitter for daily tips! @drsuepedersen 


How Plate and Tablecloth Color Can Curb Your Portions!

>> Saturday, January 21, 2012

It is well known that we tend to serve up larger portions of food on larger plates - decreasing dinnerware size is often recommended as one strategy for weight management.  However, new research suggests that it is not only the size of our plates that we should pay attention to.  It turns out that color contrast from both plate and tablecloth can affect how much we ladle up as well - and in opposite ways!

The first study, conducted by Koert Van Ittersum and Brian Wansink, asked 47 students from Georgia Tech University to serve up a target amount of cereal on small and large white plates, using black or white tablecloths as a background.  As expected, larger portions were served up on the larger plates.  What was very interesting was that when the large white plates were placed on a black tablecloth, the students served up nearly 10% more on their plate, compared to when the white plate was placed on a white tablecloth.   Also interesting was that when small white plates were used on a black tablecloth, serving sizes were underestimated.   In other words, serving sizes were more accurate when the plate and tablecloth color were the same.

The second study examined the effect of plate color on serving size.  Participants were asked to serve up pasta with a red (tomato) or a white (alfredo) sauce on red or white plates.   When the color of the pasta matched the plate, the amount of food that was ladled up was 28% larger than when the plate color contrasted with the food color.

A visual illusion, known as the Debouef illusion,  is thought to be behind these findings.  The premise behind this is that sizes (eg of food portions) appear different to us, depending on background shape sizes and colors.  Interesting!

The take home messages from these studies are to have a contrast in color between your food and your plate, but keep the color of tablecloth and plate the same.

Dr Sue Pedersen © 2012 

Follow me on Twitter for daily tips! @drsuepedersen 


Are Diabetic Men at Risk of Fertility Problems?

>> Sunday, January 15, 2012

Although diabetes is known to be associated with many complications, infertility amongst men is not traditionally thought of as being one of them.  Similarly, when a couple presents to a fertility clinic, diabetes in the man is not typically on the list of conditions to rule out.  As it turns out, diabetes in men can have an impact on fertility from several perspectives, right down to the DNA of the sperm themselves.

As reviewed by Sandro De Vignera and colleagues, the prevalence of subfertility or infertility amongst men with diabetes has been reported to be as high as 35-50% in some series, and is significantly higher than sub/infertility amongst men without diabetes.  Smoking and obesity appear to be the strongest risk factors for infertility amongst diabetic men.    

There are several mechanisms by which diabetes can be associated with fertility problems.  It is well known that diabetes can be associated with erectile dysfunction, lower testosterone levels (particularly in cases of severe insulin resistance or obesity), and retrograde ejaculation (ejaculation ‘backwards’, into the bladder). 

More recently, it has been discovered that diabetes can also be associated with damage to the DNA of sperm.  Studies suggest that diabetic men have a higher percentage of sperm with DNA damage compared to non diabetic men, and it has been postulated that this may be due to increased concentrations of ‘advanced glycation end products’ throughout the reproductive tract (proteins with sugar stuck to them, which is a consequence of elevated blood sugar over time), leading to more ‘stressed’ metabolic processes (known as ‘oxidative damage’) and thereby DNA damage.  

While several of the above mentioned elements can occur in both type 1 and type 2 diabetes, there are some differences as well.  While type 2 diabetics are more likely to suffer from the insulin resistant mechanisms of infertility (obesity, low testosterone), men with type 1 diabetes have an increased risk of concomitant autoimmunity against the developing sperm or related structures.

While this topic can be discussed in far more detail than I have presented here, the key take home message today is that diabetes may play an important role in male factor infertility.  Fertility concerns or desires should be addressed in the evaluation of the diabetic male patient, and the possibility of diabetes should be considered in a man presenting with fertility concerns.

Dr Sue Pedersen © 2012 

Follow me on Twitter for daily tips! @drsuepedersen 


Canada AM Interview: Effect of GLP-1 Analogs to Treat Diabetes and Cause Weight Loss

>> Wednesday, January 11, 2012

Dr. Sue Pedersen, an endocrinologist and metabolism specialist, says the gut hormone has proved useful in patients with diabetes, and explains the side effects of the drug.


How N.E.A.T. Are You - And Could It Be Affecting Your Weight?

>> Sunday, January 8, 2012

While the factors contributing to obesity and weight change are extremely complex, it is a truth that an increase in body weight is the result of a higher caloric intake compared to caloric expenditure (ie calories in is more than calories out).  One major risk factor for obesity appears to be our individual tendency to engage in NEAT ('non exercise activity thermogenesis'), and by making changes to one's NEATness, one may find themselves a giant NEAT leap ahead in the struggle against the bulge.

Calories Out (ie, caloric expenditure) is made up by the following constituents:
  • Basal Metabolic Rate: This is your baseline metabolism at rest, and comprises about 60% of total daily calorie burn in a relatively sendentary person.  It is determined primarily by your body size and body composition - in particular, your fat free (lean) body mass (as muscle, which is lean, is more metabolically active than fat). 
  • Thermic Effect of Food:  This refers to the calories burned by the process of digestion of food, and is responsible for about 10% of your total day's calorie burn.  This varies a little depending on what you eat, as protein takes about 25% more energy to digest than carbs or fat. 
  • Activity Thermogenesis:  These are the calories you burn by moving around.  

Activity Thermogenesis is further broken down into:
  • Exercise thermogenesis (from purposeful exercise: playing hockey, going to the gym, etc); and
  • Non Exercise Activity Thermogenesis (N.E.A.T. - there it is!).   NEAT refers to any calories burned by moving around during the day that is not related to focused exercise: this can be walking to work, moving around at the office, doing chores at home, painting a fence, playing a piano, etc.
As most people around the world do not specifically exercise, and because those that do exercise typically engage no more than a couple of hours per week, NEAT is far and away the greatest component of the total number of calories that we burn by moving around.

If we look at the explosion in obesity around the world in the last century or so, we can see that there has been a parallel decrease in our daily NEAT activities.  We have become a society that can shop online, drive to work, and purchase a self powered vacuum to clean up the crumbs around the couch from last night's TV marathon.  We have also become a society that is much more efficient in the workplace, with machines that do much of our manual labor for us, technology that allows transfer of information in an instant rather than by hand, and workplaces moved to the home as there is often no longer a reason to physically relocate oneself to an office on a daily basis. Unfortunately, this caloric 'efficiency' has taken a toll on our health as a society, making it all too easy to pack on extra pounds from the larger portion sizes and unhealthy choices that plague our marketplace.

Add to this another level of complexity: genetics.  As suggested by JA Levine, an authority on the topic of NEAT from the Endocrine Research Unit at the Mayo Clinic, it may be some of us are genetically endowed to be NEAT activators (who would have gone out to hunt in the face of famine in the 'olden days'), while others are NEAT conservers (who would tend to lay low, conserve energy, and weather out the famine until food became more plentiful again).   In modern day, a NEAT activator may be a person who is more likely to fidget, or may choose the stairs instead of the escalator; a NEAT conserver may be genetically more inclined to sit at their desk rather than stand, or may choose to drive to work rather than ride a bike in the interests of time (though the transportation issue is clearly much more complex and often environmentally determined - read more here).

So, how can we increase our NEATness?  As proposed by Dr Levine, try the STRIPE approach:

S:   SELECT a NEAT-activity that you enjoy and start it (walking to work, standing while talking on the phone, going dancing rather than to a movie);

T:   TARGET specific goals for your NEAT activity and follow through on them

R:   REWARD yourself for reaching your identified goal (eg treat yourself to a new song on iTunes to listen to after your first month of walking to work)

I:    IDENTIFY barriers & remove them (eg go to the mall to walk and talk with a friend if it gets too cold to walk outside);

P:   PLAN NEAT-activity sessions,

E:  EVALUATE yourself: have you stuck to your plan, and has it been effective in reaching your goals?

When you choose your NEAT activities, be sure that they are activities that you enjoy!  Make moving fun. :D

Thanks to my friend and Danish research colleague Mads Rosenkilde for the inspiration to write this blog, and for the heads' up on a great review article by Dr Levine.

Dr Sue © 2012

Follow me on Twitter for daily tips! @drsuepedersen


Science Behind Curbing Your Appetite With Small Frequent Meals

>> Sunday, January 1, 2012

With the holidays behind you and New Years' Resolutions in tow, take the opportunity to reevaluate your meal structure!  As part of a weight loss or weight management lifestyle strategy, it is often recommended to eat small, frequent meals, rather than having three squares a day.   A recent study, which examined the 24 hour trends in an important hormone called PYY,  sheds some new light on why small frequent meals may be so effective to curb hunger and help prevent overeating.

PYY is a hormone secreted by the gastrointestinal tract in response to a meal.  When released, PYY stimulates a sense of fullness by slowing down the emptying of the stomach, and stimulating the 'fullness centre' in the hypothalamus of the brain.  Additionally, PYY may also increase overall metabolic rate, thereby increasing our overall calorie burn.

The study, conducted by Brenna Hill and colleagues at Pennsylvania State University, looked at levels of PYY in normal weight young women over a 24 hour period.  Study participants were fed standardized meals as breakfast at 9:00AM, lunch at 12:00PM, supper at 6:00PM, and a snack at 9:00PM.  There was no significant difference in caloric content of the three main meals. 

As expected, the results showed that PYY peaks after each meal.  Interestingly, over the entire 24 hour period, the highest level of PYY was seen after lunch.  On further examination, it became evident that this high lunch time peak was due to the fact that there was an additive effect leftover from the PYY increase following the breakfast meal, which was consumed just 3 hours prior to lunch.  In other words, PYY levels had not had the chance to decrease back to baseline following breakfast by the time that study participants ate lunch.  As the supper time meal was consumed 6 hours after lunch, there was a longer duration of time for PYY to settle out, such that the peak level achieved after supper was not as high as the post lunch level.

It would follow, then, that if a person ate frequently throughout the day, that the PYY may remain elevated throughout the day, thereby keeping hunger at bay and helping to control food intake.  This is a hypothesis only, and needs to be tested in further study; other factors such as the caloric content and composition of each meal would need to be considered as well.   In order to make small frequent meals work in the battle of the bulge, these frequent meals need to be substantially lower in calorie count compared to the eating pattern of eating three squares, such that the overall calorie consumption should ideally be lower over 24 hours compared to eating three full meals.

The current study lends support to the idea that eating small frequent meals is a better eating strategy than eating three major meals, and I look forward to seeing what evolves in this interesting area of research!

Note for patients taking medication to treat diabetes: It is important to discuss any possible change in eating habits with your doctor, before making any dietary changes.  Some medications that treat diabetes, including some oral medications as well as insulin, are dosed to control your blood sugar after a meal.  These medications may need adjustment with a change in eating plan.  For patients using meal time insulin, some types of mealtime insulin are easier to incorporate into a smaller, more frequent meal plan than others - talk to your doctor and your diabetes health care team to work out a plan especially for you!

Dr. Sue © 2012

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I am excited that you have arrived at my site, and I hope you are too - consider this the first step towards a Healthier New You!! As a medical doctor, Endocrinologist, and obesity specialist, I am absolutely passionate about helping people with weight management. Though there is certainly no magic cure for obesity, there IS a successful treatment plan out there for you - it is all about understanding the elements that contribute to your personal weight struggle, and then finding the treatment plan that suits your needs and your lifestyle. The way to finding your personal solution is to learn as much as you can about obesity: how our toxic environment has shaped us into an overweight society; the diversity of contributors to obesity; and what the treatment options out there are really all about. Knowledge Is Power!!

Are you ready to change your life? Let's begin our journey together, towards a healthier, happier you!!

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