FitBit Calories Burned Accuracy? Compared to Calories In...

[Jack12312]

I've been using my FitBit Charge 2 for approx. 1 year now, so I'd like to think it has a pretty good baseline. 

I'm curious of the accuracy of the calories burned section of the device. My average calories burned per day (taken from last week) is 3671. I am 24, 183cm, 77.4kg and 17% BF.

According to my Fitbit my BMR is 1824. 

I have an office job, so I'm pretty sedentary in the mornings, but I aim for 10K steps per day (which is frequently hit). I am in the gym 5 days a week weight training with some cardio (100 - 200 kcals burned per cardio session (tracked through fitbit) 2-3/5 days). 

I'd like to say i'm pretty active. The only issue is that my calories in comes nowhere near this 3600 mark. I'm currently on 2400 and my bodyweight has small fluctuations as normal, and my BF% is sitting around the 16-17% mark. It has been this way for a significant amount of time now (approx. 2 months). I attempted to raise my calories, but the weight gain was far too rapid with a significant BF increase also. 

In a time where I'm looking to gain some size, my Charge 2 is telling me that I need to consume in excess of 3800 calories per day, whereas the reality is that with my current composition, that would balloon me. 

Any help is greatly appreciated.

[SunsetRunner]

When you say the weight gain was rapid, are you talking about the number on the scale or like you can see a fat increase on your body? Don’t worry about the scale. People get so worked up about the number on the scale when that tells you nothing. What matters are how your clothes fit, body measurements, and whether or not you are improving in the gym. I wouldn’t jump from 2400 to 3800 calories all in one shot. Slowly add back in calories, 100 calories per week. When you are in a calorie deficit for a while your body sees that as the new norm. The metabolism is really good at adapting. So when you increase calories your body will likely store that as fat because your metabolism has already adapted to the low calories. Now your body has to get used to the new norm with increased calories. Give it some time and your metabolism will adapt to the higher amount of calories. When you get close to your calculated TDEE (3600 calories) watch for weight gain that doesn’t stabilize. When your weight doesn’t stabilize drop calories back down a little bit and that is your maintenance. I personally feel the calories Fitbit gives is fairly accurate. The problem is people tend to drop calories so fast and for too long that their metabolisms just tanks and of course, freak out when they try to add back in calories. You have to give it time to adjust.

[Jack12312]

I’m talking about in a visual Bf increase and also an increase in BF when worked out through callipers/body analyser scales.

I would never make that jump straight away. I feel exactly into that trap the last year or so of having a caloric consumption of far below what I should have had, resulting in that tanking of my metabolism. Since October I’ve been steadily increasing starting at 50-100 every 3 weeks or so, just to minimise the gain, but where my confusion has come is an increase in BF when I’m reaching around 2400 - 2600. Maybe it is my metabolism getting used to it again, but still I’m just confused really. Either my body is far off the mark or my Fitbit is. 

Thanks for your reply. I just want other’s opinions on the matter I’m racking my brain after calculating my BMR and estimating my TDEE 1000 times to see if the numbers add up to the gain in BF.

[SunsetRunner]

Okay, so you were eating less than 2400 calories. It sounds like you are pretty active even though you have a sedentary job. I’m the same way. I’m a stay-at-home mom but I workout 2 hours every day. I don’t have much going on during the day. I’m older than you but my stats are pretty close to yours. I would think you are still fairly low in calories. I’m actually currently reverse dieting too. I alternate how many calories I consume during the week because it keeps my metabolism guessing – something you may want to consider doing. My low being 2000, moderate being 2200, and high being 3200. My calculated TDEE is approximately 2800 calories. I would assume your maintenance should be higher than mine. It could be what you are eating too. If you are consuming a lot of fast digesting carbs you are basically fighting a fight that can’t be won. You would be making it hard for yourself. I would still advise reverse dieting. As I said, you will gain fat because the ~2400 calories is now your new maintenance but give it time to adjust. Don't give up.

[Jack12312]

Yeah I do believe I am still relatively low in my calories compared to what I should be consuming. I guess it's one of those things. My daily weigh in showed a decrease in BF this morning, which is interesting - i've never seen such a fluctuation in BF% before, so that's one for the experience book. 

I've attempted carb and calorie cycling before, but it just doesn't fit with my lifestyle. Will continue to reverse diet at a slow pace. I'll update this with future findings, incase anybody are experiencing the same issues and confusion.