Weight loss vs body fat %

[flatlinedisaste]

Okay let me start by saying I have been using my fitbit charge for 3 weeks along with my Aria scale. I started at 315lb and am now down to 302 (yay me) anyways my weigh in today it showed me lose my 3 pounds but says my body fat % went up. How exactly does this work? Am I burning muscle and storing fat? lol please explain, thanks! (also my brother who also uses a charge and aria scale, it said he gained 8 pounds but his body fat % went down, we are really confused about the body fat %)

[Heybales]

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@flatlinedisaste wrote:

Okay let me start by saying I have been using my fitbit charge for 3 weeks along with my Aria scale. I started at 315lb and am now down to 302 (yay me) anyways my weigh in today it showed me lose my 3 pounds but says my body fat % went up. How exactly does this work? Am I burning muscle and storing fat? lol please explain, thanks! (also my brother who also uses a charge and aria scale, it said he gained 8 pounds but his body fat % went down, we are really confused about the body fat %)

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Inaccuracy - totally the inaccuracy.

You may if the stars are aligned just right get upwards of 5% accuracy on the BF%.

But even if you present the exact same hydrated body, level is probably closer to upwards of 10%.

So you are still well within the range of accuracy overlap at each weigh-in.

Also, since BF is a %, it doesn't mean you stored fat, you just lost more making the BF% go up, the raw value can still decrease for that to happen with the math.

That being said, if you really lost 13 lbs in 3 weeks, that would imply for it to be ONLY fat the following.

13 lbs x 3500 cal / 21 days = 2167 cal deficit daily. Because fat as energy supplies about 3500 calories.

So for that weight to be only fat, you would had to have burned 2167 calories more than you ate, each and every day on average.

Obviously that is highly unlikely.

Of course some was water weight you lost. Say 5 lbs to be generous. So then 8lbs of fat?

8 lbs x 3500 / 21 days = 1333 cal deficit daily.

If you really accomplished that on average daily, then it's possible you only burned fat. That's still high.

I'm betting highly unlikely, and so the amount of calories in a pound of muscle used as energy is only 600, therefore throwing that equation off.

Unless you are doing full body strength training, eating reasonable deficit, and eating enough protein - yes you have burned off probably around the expected 20% muscle mass.

So about 1.6 lbs muscle. 6.4 lbs fat.

6.4 x 3500 / 21 = 1067 deficit

1.6 x 600 / 21 = 46 deficit

1113 average daily deficit.

I'm betting that one looks closer to reality.

[Heybales]

Oh yeah, only want to use a valid weigh-in day.

Morning after rest day eating normal sodium levels, not sore from last workout.

Those are known water fluctuations, and that increases non-fat weight, which would make it appear you didn't lose that much fat, or went the other direction.

If your first weigh-in wasn't valid, or the later ones - throw them out. Inaccurate data is worse than no data.

[flatlinedisaste]

Thank you for the quick reply. I am burning roughly 1000-1300 more cal a day than I take in. All I am doing is walking and getting 10-15k steps a day..sometimes 18-20k.

[Heybales]

Then my last example does apply.

You have lost muscle mass.

[flatlinedisaste]

I weigh in every sunday night. not sure if I should do it in the morning or not. My first week I lost 10lb, 2nd week gained 1 lb. and this week lost 3lb. which I'm sure some is water weight as you have stated.

[Heybales]

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@flatlinedisaste wrote:

I weigh in every sunday night. not sure if I should do it in the morning or not. My first week I lost 10lb, 2nd week gained 1 lb. and this week lost 3lb. which I'm sure some is water weight as you have stated.

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Gave valid weigh-in time above.

[flatlinedisaste]

Thanks, yeah I never have a rest day lol