Body Fat after Five Days

[Runecrow]

So, basically, 2017 was a rough year for me so I slowly gained weight and then comfort ate 30+ lbs in a 6 month time period after that.  I recently saw my new doctor for an initial visit and he didn't seem too convinced that I could drop it and become healthier in the 4 months leading up to my follow up in May.  That lit a fire in me and I got serious about eating healthier and finding ways to get more active even when my schedule does everything it can to be in the way and prevent it.

I weighed myself using my Aria on Saturday the 20th but didn't officially start working towards my goal until the 22nd.  From the 22nd to the 26th I stayed at the lower end of my calorie goal and managed around 30 minutes a day of active calories.  I weighed myself this past Saturday morning, with low expectations, only to see that I had lost 7.1 lbs and 5.1% body fat.  I know water weight plays a large role in the first week of weight loss, but the body fat number is what really surprised me.  Is the Aria just super inaccurate in measuring body fat?

[WavyDavey]

Bodyfat scales are pretty sensitive to swings in water weight. So gaining or losing water can cause big fluctuations in the bodyfat readings. In a couple of weeks you should see the % stabilize. Keep up the good work.

[Dominique · Accepted solution]

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wrote:

Is the Aria just super inaccurate in measuring body fat?

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First of all, it does not measure body fat, but rather estimate it. As @WavyDavey said, the method used by BIA scales is very sensitive to hydration. Your 7.1 lbs weight loss in about 10 days suggests a large part of it is water fluctuation. Have you switched to a low-carb diet? Drastically cutting carbs usually results in a big drop in water weight (because for each gram of carb stored in your glycogen, there are about three grams of water stored there too).

If you want to make optimal use of the BF% estimate, you should weigh yourself in the same conditions all the time. For most people, this means first thing in the morning, after trip to the bathroom and before eating or drinking anything. You should also look at trends over a longer period of time (several weeks to several months), as opposed to day-to-day fluctuations. For that, you may consider linking your Fitbit account to TrendWeight (see link in my signature), which provides a smoothed moving average that lets you better see where your weight and BF% are heading.

[Runecrow]

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wrote:

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wrote:

Is the Aria just super inaccurate in measuring body fat?

---

First of all, it does not measure body fat, but rather estimate it. As @WavyDavey said, the method used by BIA scales is very sensitive to hydration. Your 7.1 lbs weight loss in about 10 days suggests a large part of it is water fluctuation. Have you switched to a low-carb diet? Drastically cutting carbs usually results in a big drop in water weight (because for each gram of carb stored in your glycogen, there are about three grams of water stored there too).

If you want to make optimal use of the BF% estimate, you should weigh yourself in the same conditions all the time. For most people, this means first thing in the morning, after trip to the bathroom and before eating or drinking anything. You should also look at trends over a longer period of time (several weeks to several months), as opposed to day-to-day fluctuations. For that, you may consider linking your Fitbit account to TrendWeight (see link in my signature), which provides a smoothed moving average that lets you better see where your weight and BF% are heading.

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I actually haven't switched to any specific type of diet.  I basically went from eating fast food every day and taking in about 3000 calories to getting an average of about 1500 calories a day and making sure I close all my rings on my watch, including 30 minutes of exercise by walking for about 5 minutes for almost every hour at work (or at least getting the 250 steps for my Fitbit if I'm too busy to take more than a minute or two).

I had a feeling that the loss of water weight may have affected the body fat percentage in this initial week, but I wasn't certain and a quick search online didn't yield any results other than saying that maybe 1% over a certain time period was normal, which really made me question the sharp drop.

Thanks for the replies. 🙂

Edit:  I just wanted to add that my weigh-in time is always on Saturday just after I wake up and use the restroom and before I eat or drink anything.

[Dominique]

Any sudden disruption in your diet and/or your activity level will likely have an effect on water retension, and therefore affect the readings of body fat on the scale. Halving your calories would definitely be such a disruption.

My eating and activity patterns are very regular: I eat more or less the same things and same amounts everyday, same with exercise. Fluctuations in BF% within any given month is usually within a 1% range.

[Runecrow]

I just wanted to follow up that on my second-week weigh-in (in which I only lost 1 pound), I noticed that I totally misread the first week's results.  While the weight I wrote was accurate, it didn't say I lost 5% body fat but that I had actually gained 5% body fat.  That actually makes more sense to me with the loss of water weight if you consider that less of my body composition is water, so that would mean the other parts of the composition would go up in percentage.  During the week that I lost 1 pound (last week), the body fat percentage dropped back down  2.2%, which leads me to believe that I actually lost fat (or perhaps gained more lean muscle, as well as losing fat, from being a bit more active) during that week.

Anyway, I just wanted to correct my bad info in my first post.  Again, thanks for the replies, earlier. 🙂