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Caution FitBit HR Wearers - Don't Trust That Your Heart Rate Is Accurate!

>> Wednesday, January 27, 2016

In the effort to track calorie burn and activity, I have seen many patients coming in wearing a FitBit HR.  So, I decided to get one myself to check it out.

I use a Garmin to track my heart rate during exercise, which requires a sometimes uncomfortable chest strap, so the idea of tracking my heart rate with my neat little FitBit HR wrist band was very appealing indeed.

Unfortunately, what I have found is very disappointing - for me, the FitBit is completely useless to track higher heart rates (and based on online reviews and even lawsuits in the US, I am not the only one).

When I am at rest, my FitBit HR measures my heart rate very well.   Now, watch what happens when I put the pedal to the metal on my spin bike.  Pictured below is my Garmin (white watch, left), measuring my heart rate via the chest strap; on the right is my FitBit HR.

While my actual heart rate was 167, my FitBit HR registered only 108.  

This is beyond shockingly inaccurate and actually quite dangerous - for example, if a person with a heart condition has been advised to keep their heart rate under a certain target, the FitBit HR could dramatically underestimate their actual heart rate and mislead the person to think they are under their maximum target when they are not.

When I drove my output near my max with a heart rate of 180, the FitBitHR didn't register at all, which is safer, as at least it is not misleading the wearer with a wildly incorrect heart rate:

***NOTE: Discuss with your doctor to find out what your appropriate target and/or maximum heart rate should be before embarking on an exercise program. ***

It was only after I had stopped my exercise and my heart rate came down into the 120s that the FitBitHR became accurate again:


For those who are wondering if the problem could be the Garmin, it's not - I checked each of these heart rates manually against my own pulse, and the Garmin was accurate (though it too can be inaccurate, for example if you are in a cold environment and/or not sweating).  I have also carried out this experiment with different activities, and yes, I have also tried moving the FitBit HR further up my wrist. The results are the same.

The reason for the inaccuracy comes from the technology used to monitor HR.  While the Garmin strap uses electrical activity from the heart measured via the chest strap, the FitBit HR use optical technology to measure heart rate.  This involves using a LED light to illuminate your capillaries (tiny blood vessels) as blood runs past.  Capillary blood flow isn't as distinctly pulsatile as the bigger blood vessels (arteries), and at higher heart rates, it may be very difficult for this technology to distinguish higher heart rates.    I have not tested any of the other wrist devices using optical technology out there, but I suspect they may be at risk of similar inaccuracies.

What I do like about my FitBit HR is the sleep tracker, and the pedometer (step counter) - though both of these features have their limitations as well.

Thus, please exercise caution in your interpretation of your FitBit HR data - your heart rate, particularly during activity, may be highly inaccurate.

***NOTE: Before starting any moderate or vigorous exercise program, be sure to speak with your doctor.***

Thanks so much to Ryan, Jacqueline, and friends for the fabulous discussion that led to this blog post.

Follow me on twitter! @drsuepedersen © 2016


PREdiabetes May Cause Kidney Damage

>> Wednesday, January 20, 2016

In our quest to control blood sugars of people who have diabetes, one of the 'small blood vessel' complications of diabetes that we are trying to prevent is damage to the kidneys.  For people who have prediabetes, it has generally been thought that they do not have an increased risk of small vessel disease.  However, there is mounting evidence that prediabetes may in fact cause small vessel damage; a new study suggests that prediabetes may in fact cause kidney damage.

First, let's talk about what we mean when we say 'prediabetes'.  Diabetes and prediabetes are defined on the basis of how high blood sugars are.   Quite simply, prediabetic blood sugars are lower than diabetic range blood sugars, but higher than normal blood sugars.  For the exact blood sugar definitions in Canada, please see Table 2 (diabetes) and Table 4 (prediabetes) here.

A study suggesting that prediabetes causes kidney damage was published in the American Journal of Kidney Diseases.  The study was a prospective cohort study that followed 1,261 people without diabetes between the ages of 50-62 for a median time of 5.6 years.  Participants who had prediabetes at the start of the study were at nearly 2 times higher risk of having hyperfiltration (an early manifestation of diabetic kidney disease), and at 1.8 times higher risk of having higher-normal albumin levels in their urine, compared to those with normal blood sugars (albumin in the urine is also a diabetes-related kidney complication). These changes were seen independently of other risk factors such as blood pressure at baseline, and independent of changes in blood pressure medications.

That prediabetes can cause complications before diabetes develops has a profound impact, in that 1 in 4 Canadian adults has diabetes or prediabetes, with most of those being prediabetic.  (In USA, 44% of American adults have diabetes or prediabetes).  Most people with prediabetes do not know that they have this condition, as there are usually no symptoms of this condition.

While the notion that prediabetes can cause small blood vessel complications is relatively new, it is known that prediabetes (especially impaired glucose tolerance) are at a substantially higher risk of developing BIG vessel complications (eg heart disease).

Knowing that prediabetes can cause organ damage makes two things very clear:

1.  We need to be checking for prediabetes in people who are at risk; and

2.   We need to aggressively prevent and treat prediabetes.

Follow me on twitter! @drsuepedersen © 2016


#Active365 Goes Public!

>> Tuesday, January 12, 2016

Here's a chance to get motivated to stick with those New Year's resolutions you're trying to keep.

Lisa Taylor, a Calgary high school teacher (and, I'm proud to say, my amazing sister), launched a Twitter initiative #active365 to help her phys ed students feel inspired to engage in daily physical activity.  When they get active, they take a picture and post it on Twitter - this gets their classmates hyped about being active, stimulates some friendly competition - and Miss Taylor even gives them bonus marks towards their report card!

We are now taking #active365 outside of gym class and to the general public!  Here's your chance to get friends, family, and work colleagues involved and see who can rack up the most #active365 tweets each week, each month, and for all of 2016.  Being #active365 will mean different things to different people - it can mean walking to work or school instead of using a car or bus; taking the stairs instead of the elevator; taking your kids for a swim in the local pool; going to the gym; ice skating; starting a new exercise class... use your imagination!  You can choose to tweet with or without a picture, but be sure to describe what you did!

So start racking up those bonus marks to your health - let's tweet up #active365 and motivate each other every day of the year!

I would love to know when my readers are Tweeting at #active365 - my Twitter handle is @drsuepedersen - please add it to your Tweet so I can cheer you on!

Important note: Be sure to discuss with your doctor before starting any new activity or exercise program. 

Follow me on twitter! @drsuepedersen © 2016


Hot Topics!

>> Thursday, January 7, 2016

Happy New Year!  I hope everyone's 2016 is off to a fantastic start.

I received a really neat eTOC from The Obesity Society summarizing their top articles of 2015 last week (including how an apéretif causes us to eat more; that drinking water before meals may help with weight loss; and the effects of different types of physical activity on waist circumference).

Loving this idea, I thought I'd share with you some of my favorite and/or most popular posts from 2015.  Enjoy!

Dr Oz Fails The True Test Of Research

Secrets To Success: Keeping Weight Off

Could Artificial Sweeteners Cause Diabetes? 

Mediterranean Diet With Olive Oil Prevents Breast Cancer

Why Is It So Hard To Prevent Weight Regain?  Part 1, Part 2, and Part 3

Much more exciting news in store on in 2016 and beyond - stay tuned!

Follow me on twitter! @drsuepedersen © 2016



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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