How accurate is a FitBit at estimating calorie burn?

Photo(1)Last month, I did a little experiment with my FitBit Flex to see if being in a 250-calorie-per-day deficit actually does lead to half a pound per week of fat loss (because there are 3,500 calories in a pound of fat, so 7 days x -250 calories less per day = -1,750 less per week).

I tracked my caloric intake closely using MyFitnessPal in conjunction with my FitBit, and added in any workouts using calories tracked from my heart rate monitor (I burn much less than what my FitBit estimates, so I manually enter in these calories burnt and it recalculates), trying to stay within the range of a 1,750-calorie-per-week deficit. Here are the results:




deficitThe measurements on the left were taken on December 30, 2013, and the measurements on the right were taken January 30, 2014.

So is the FitBit accurate at predicting calorie burn? It’s pretty darn close. I find it tends to overestimate calorie burn during activities, such as walking or running, so if you don’t have a separate heart rate monitor to calculate your exact calorie burn it will take longer to see fat loss results.

This brings me to another point, though. Fat loss really is just simple math; if you eat more than you burn, you will gain weight. If you burn more than you eat, you will lose weight. If you eat what you burn, your weight will stay the same. There are no gimmicks, tricks and secrets to fat loss. There are supplements, however, that do help to decrease body fat and increase muscle mass… but guess what, they’re illegal (*couch* anabolic steroids *cough*) and the side effects (shrinks testicles, lowers sperm count, increases body hair, mood swings, etc.) aren’t worth it.

Here’s an interesting video James Fell of Body for Wife and SixPackAbs fame shared the other day on Facebook that kind of drives home this point — and reveals that what many of us think is a “metabolism problem”, is actually just us grossly underestimating how much we’re really eating.

So why all this fat loss crap I’ve been blogging about lately? I’m about halfway through studying for my CSCS exam (which is on May 10!), and am right in the thick of learning about the way the body works at a cellular level. Also, I’m hoping to find a few “practice clients” to train when I get into program design. I’m excited to announce I’ll be interning at Victoria Wellness Professionals a few times a week, just to get some learning experience in the type of environment I hope to train clients in when I’m certified. Victoria Wellness Professionals is a private studio that provides both sport-specific and general health and fitness training, with a focus on science-based training and education. I’m super excited to finally get some “in-the-trenches” experience before I take my exam, so I’m as prepared as I can be.


Stay tuned for a blog announcement/call out for practice clients (basically I want to train you for free for 3-6 weeks, online or in-person) in the coming weeks!