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I started working out again about 2 months ago, following a long period of inactivity, currently my body fat percentage is around 12% my goal is to get it down to 6%-8%. I'm on a low-fat high-protein diet (I make sure I get at least 2g of protein per kg) and I do 3 days of lifting followed by 20-30 mins of cardio (jogging) and the other 3 days I do 20 mins of aerobics and skipping rope.

Unfortunately I've just started tracking my progress two weeks ago, as you can see it doesn't seem to be slowing down, I lose around 0.5kg per week, however, I can't make sense of the data, what are those peaks after every weight loss, and why do they seem to be getting smaller ? will I eventually stop losing weight or is this a good thing ? I was thinking maybe it has something to do with water retention, or am I doing something wrong here ?

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Update:

I take my weight every morning after going to the bathroom and before breakfast, at the same time, also when I started I was around 74Kg.

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2 Answers 2

up vote 4 down vote accepted

You are interpreting too much into too little data.

You will always have daily peaks with no apparent reason, this depends on how well you digest, how much you drink (and let go) etc. I weighed myself over the past year - sometimes more than once daily - and as you can see only the long term curve really is interesting.

weight curve

Note the peak around the holidays (christmas and new years eve).
The rise in February was due to a project I had to work on, where I spent most of the time in front of the computer, eating pizza and finishing the evening with some beers. (So no workouts and no calorie-counting)

Of course you don't have to weigh yourself more than once a day, however, try to do it at the same time of the day (eg after toilet, before breakfast).
I only did it because it was fun to do, I need this aspect of gamification to keep me motivated. And it is funny to observe differences in weight before a tour with the bike and afterwards.

If you are lifting you will build muscle, too. Don't focus too much on loosing weight, so you don't interfere with the process of muscle generation.

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I do weigh myself every morning after going to the bathroom and before breakfast, I know I have too little data, but I was thinking if this pattern continues, the peaks will keep getting smaller, will I stop losing weight or is it that my body doesn't retain water as it used to and my weight loss will be more linear ? –  mux Mar 29 '13 at 13:02
    
As there are only two peaks in your data, one more extreme than the other, I would not think about it too long, it's probably just coincidence. I have these ups and downs myself (even when comparing just the morning data), and I have not been able to observe a pattern. –  Baarn Mar 29 '13 at 13:09
    
It might be possible - as the peaks look like a 6-8 day pattern - that they are somehow related to your training or a weekly pattern you have in your diet (eg shakes you consume during workout, but not on the weekend), but I still think you need more data to confirm this. In the end it is the average over some days that should count (or the result you can observe in the mirror). –  Baarn Mar 29 '13 at 13:12
    
I'm actually very consistent all week with my diet and workout, but you're right I'm probably obsessing way too much about it. Thanks. By the way, there's a third peak on the 12th day at 68.4 :) –  mux Mar 29 '13 at 13:33
    
+1 for the last 2 sentences. If you are lifting while exercising, I would focus more on how you actually look and feel, instead of the weight itself. –  Taylor K. Mar 29 '13 at 14:42

There's some good discussion of this in John Walker's book The Hacker's Diet. Here's a quote from a chapter called "The Rubber Bag".

Consider this view of human as rubber bag presented at a NASA conference on the exploration of Mars.

NASA

From this all-inclusive perspective, which accounts for the oxygen in the air we breathe, moisture lost through the skin, and water generated by the reactions that break down the food we eat and reassemble it into the cells of our body, a human being [...] resembles a water pump [...] Most of the changes in weight you see have nothing to do with how many calories you're eating or burning. Instead, all you're seeing is how many pounds of water happen to be inside the rubber bag at the moment.

Small changes in a flux of 6Kg/day can change your weight considerably. I've been tracking my weight for almost a year in a similar manner to you, and I find that the day after I go running, I frequently lose up to 2KG or around 2.5% of body mass! I then proceed to gain all that back over the next two days, and I'm back approximately where I started. My theory is that I'm depleting/replenishing my glycogen stores, which take up several times their weight in water, though other factors are presumably at work. In any case, daily fluctuations of 2Kg are in no way uncommon for me, and they're probably unavoidable. Walker suggests using a (smoothed) moving average to factor out daily fluctuations, and only look at the trend line, which has worked well for me.

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