Why does my body fat go up when my weight goes down?

OU812

I've noticed this over time, it seems that overtime my weight goes down, my body fat goes up. This is from my fitbit report:

Today at 7:30 Measurement13 st 6.4 lbs 28.7% fat
Sunday 23 Aug at 10:54 Measurement13 st 6.1 lbs 28.4% fat
Saturday 22 Aug at 9:06 Measurement13 st 7.2 lbs 28.2% fat
Friday 21 Aug at 7:40 Measurement13 st 9.3 lbs 28.2% fat
Thursday 20 Aug at 7:47 Measurement13 st 8.3 lbs 28.2% fat
Wednesday 19 Aug at 7:46 Measurement13 st 8.6 lbs 28.2% fat
Tuesday 18 Aug at 7:32 Measurement13 st 9.1 lbs 28.1% fat
Monday 17 Aug at 7:37 Measurement13 st 10 lbs 28.1% fat
Sunday 16 Aug at 11:25 Measurement13 st 9.1 lbs 28.1% fat
Saturday 15 Aug at 9:06 Measurement13 st 8.5 lbs 28.2% fat

Alf Veedersane

The bodyfat measurement isn't hugely accurate. One thing that affects it could be the level of hydration.

It's only a snapshot over ~9 days...It might be water weight that's causing the drop in weight which would mean the bf increase makes sense

Sky King

Correct me if I am wrong here, but I highly doubt that any kind of home body fat measurement could be accurate to under 0.5% tolerance, could it?

Oryx

Those machines arent that accurate. And you're weighing yourself too much. A weekly check is a better guide than a daily check which can fluctuate depending on whether you took a drink, or had a poop!

OU812

It's a Fitbit aria scale I'm using btw (if that makes any difference)

brownej

I think you may have an unrealistic expectation on what to expect from your scales.
From the 10 days of measurements you posted it appears that your weight is static +/-1.8lbs and your body fat is static +/- 0.3%. It is varying within a very tight band.
Are you doing something that would lead you to expect your weight and bodyfat to be changing drastically over a relatively short period like 10 days.
The scales uses an impedence measurement for your body fat and this method isn't hugely accurate as it can be affected by anything that affects the electrical impedence of your body. Hydration levels, electrolyte levels etc all play a part. If you went to the cinema and had a big bag of popcorn your fat measurements would be different before and after using a bio impedence measurement. The morning after a big night out would also give you different results.
For best results you should measure yourself at the same time every day, first thing in the morning is good.
As the brochure for your scales says
"Short-term fluctuations in weight don’t give you a realistic picture of your health and fitness–It’s the long term trends that matter."

the groutch

brownej wrote: »

For best results you should measure yourself at the same time every day, first thing in the morning is good.

for best results weigh yourself one a week at most.

OU812

brownej wrote: »

Are you doing something that would lead you to expect your weight and bodyfat to be changing drastically over a relatively short period like 10 days.

I'm a year and a half into loosing weight now. I was almost 24lbs heavier when I started. Unfortunately Summertime is a problem for me with kids off school as I've no childcare for when I usually go on a 5-7k walk (got that in most days).

I tried weighing myself every week but wasn't happy with the results, it wasn't motivating enough. Hopefully now with the schools back next week I'll be back walking. Want to lose another albs & then maintain it.

Alf Veedersane

My weight is pretty stable but it fluctuates up and down across a range of ~ 2kg when I've weighed daily.

Weekly is more indicative of a trend. Changes daily could be down to a few things like hydration.

But the body fat measurement is always going to be a rough approximation rather than an accurate measurement

Mellor

There's very little fluctuation in those numbers tbh. Those scales are not nearly accurate enough to deal with 0.1% changes. i'd go as far to ignore the bf% and just look at the weight. BF% is bounc all over the place, but by the time you drop a stone, it'll be bouncing around the 23's

Carlos Orange

People generally seem to be advising to weigh weekly but I weigh myself daily. I don't think it really matters since weighing yourself is just a way to measure results. The results are driven by your actual behaviour. Just don't obsess too much about daily fluctuations , up or down and remember whatever is happening your weight is going to fluctuate in a range (1-3KG for me) during a week. All that matters is the trend and it is going to take 3 or 4 weeks of measurements to see that.