Fitbit's weight lose calculations - dangerous for me?

[HybridHayley]

So I am a little concerned with the personalised calculations generated via Fitbit.

I am 25 years old, 5ft, weight 105lb and sedimentary job.

I run three times a week burning 200 odd calories each time, work in an office environment in which I occasionally cycle to burning about average 72 calories and my BMR is around 1152 according to Fitbit/assessments burning 12 calories every 15 mins.

I have put myself on a plan to loose 1lb a week. Fitbit is estimating on an average day that I will burn about 1300-1500 ish calories a day - 1200 on a very sedimentary day. Now giving that I want to loose 1lb a week I should then -500 calories to keep the weight lose. I only want to loose a few pounds to remove some leg and yummy fat so I can work on building muscle instead. 

So giving the calculations I need to eat between 800-1000 calories a day.

Now my question is ... if I need 1152 to just about function which isnt including any activities like walking or moving about then shouldn't my minimum calorie intake be 1152 not 1400 - 500 = 900. Eating 900 calories a day just seems dangerous!

At the minute its estimating that I will burn probably about 1485 today, which means I get to eat 985 in which I only have 210 left for the day...

I am I doing this wrong or...

The only solution I can see is to exercise everyday and bring my calorie burn up to 1800 so that I can eat at least 1300, this is doing an extra 300 odd worth of exercises everyday so I can actually have a decent meal.

I would love your opinion and Fitbits.

Thanks

Hayley

[Mukluk4]

You can't target weight loss.  I would instead go ahead and build muscle which you can focus on target areas and the fat will burn away/minimize.

[SunsetRunner]

Trust your instincts. There is no way, at your weight/height, you can or should lose 1 pound a week. You are at a healthy BMI. Focus on strength training and staying fit, rather than losing weight. You cannot lose weight just from your legs or tummy, but you can change your shape by lifting, etc.

[HybridHayley]

I understand you cant target weight lose, I also understand that when you loose weight that it comes off everywhere not certain areas in which you work and I understand that doing 20 crunches each day wont make that area lean but just improve the muscles you are working on. 🙂 

My aim is to loose about 4-5 pounds as my body analysis estimated that I am carrying 35% of body fat. I have a small frame and I have ok fitness (running 4.1km, aiming for a 5km +), but you can tell that my body is mostly fat not muscle. I dont want to get bigger but keep the same size but become lean with some muscle. Dropping a few pounds still keeps in a healthy BMI.

You probably all think I am crazy haha! But I am slim but carry too much fat in comparsion to my size... these boobs need to shrink too. Swapping fat for muscle is the goal 🙂  

[JohnRi]

First of all a 500 calorie deficit is really for people who want to lose 20 lbs.  A 250 calorie deficit is more practical for losing under 10 lbs. 

Second, you probably should eat at least 1300 calories a day.  So yes, can't maintain a 250 calorie deficit, you will have to exercise so that you can eat at least that much.  I'm at the tail end of maintaining a 1000 calorie deficit, about to switch to 750 when I get to 40 lbs from goal.  I have to exercise for an hour everyday to make my goal.  As I lose weight I burn fewer and fewer calories each day.  Which one of reasons I have to go to 750 deficit.  Even with 90-120 minutes of exercise, I soon will not be able to make a 1000 calorie deficit.

I'm curious how you came up with a 35% body fat.  I'm still 46 lbs from my goal, and I'm 32% right now.  Granted I'm a 6 foot tall man, so it's not the same. 

But I also agree with the other posters, you are just going to have to exercise the rest off.  Keeping a diet of 500 calorie deficit, will make it very hard to add muscle.  Not impossible, but very hard.  You would have to eat a diet, high in protein, low in fat and carbs. 

My suggestion is eat a heathly diet around the calories you burn each day.  Maybe a little lower 100-200 calories.  Eat a high protein diet, spend your time doing cardio and strength training.  Hit the gym, and lift the weights.  Running 4.1 km is probably around 20-30 minutes for you.  You should increase that to at least an hour.  If you can't run for an hour, try running for 30 minutes, and walking for 30 minutes.  Also try different exercises each day.  Running, swimming, biking, cardio class, etc.  Changing things up each day exercises, tones and strengthens different muscles.

It's going to be a painfully SLOW process.  But give it a few MONTHS and you should be there.

[Dominique]

Your BMI is already very low (19.7). Your being on the lower end of the normal range would make a case for losing weight as slowly as possible. One could of course question whether it is necessary at all for you to lose weight, but if you have decided to go for it, I would would advise to settle for a lower weight loss rate: for instance, 0.5 pound per week, which would translate into a 250 calories deficit. With a very active lifestyle, you could burn 1800-1900 calories per day. With a 250 calories deficit, you would still be able to eat 1550-1650 calories. That’s already a decent amount to eat. Assuming you’d only be looking to lose 5 pounds, it doesn’t really matter whether you do it in 5 weeks or 10 weeks (still leaves plenty of time before bikini season!).

As already stated, you cannot "spot-reduce". Since you’re already quite thin, what little fat you have left is bound to be "stubborn" fat, the one that is the trickiest to lose. I’d include resistance training in your program right away, rather than waiting for the fat loss to be taken care of first. Resistance training may not  cause fat to melt, but it won’t add it either (if you’re eating at a deficit).

[HybridHayley]

Thanks for the advice 🙂

I had a body analysis done by a gym (one of them ones where you stand on metal plates and hold metal things then it measures your for all sorts) I was mortified then I see the results. Basically, I am weak with very little muscle and covering it is fat. at the 35% mark. I dont know how accurate these mechines are but it gave me some insite. 

After prodding and poking, there isnt one lean area apart from my neck haha!

Doing the maths is just scary but my main concern is that if people my size trust fitbit and there weight lose know how... then it can below a real health problem. At least myfitnesspal wont allow me to complete my entry with less than 1000 calories a day. Fitbit says I only have so much left which is under 1000!

It's definately something to think about and is a dangerous flaw in there calculations!

Thanks for the tips though, I didnt know that these targets were for bigger people. The reason why I want to loose some fat first is because I know full well I would have to pile on the protein and calories when I am serious with working on leaness and strength.

I started running in January from not being able to run 60 secs to running nearly 30 mins. I am heading for a goal of 5km then 10 km so its a massive improvement already from January in terms of my cardio. 

Next to join in some strength training and endurance to accommodate it.

[Dominique]

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@HybridHayley wrote:

I had a body analysis done by a gym (one of them ones where you stand on metal plates and hold metal things then it measures your for all sorts) I was mortified then I see the results. Basically, I am weak with very little muscle and covering it is fat. at the 35% mark. I dont know how accurate these mechines are but it gave me some insite.

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I wouldn’t put too much faith in these body analysis devices. Have a look at the pictures of women with various body fat % in this link: chances are you are not in between the 35% and the 40% photo. If you want to have a reliable estimation of your real body fat %, you should get a BodPod or DEXA scan done.

Devices that use bioimpedance (like the Fitbit Aria) can be useful if/when used repeatedly under the same conditions (e.g. always at the same time of the day, usually first thing in the morning). Bioimpedance scales may not give you body fat % that are accurate in absolute terms, but they will usually let you track relative trends. At least, it has been my experience with the Fitbit Aria, which I have now been using for close to three years.

[Mukluk4]

Thanks for the tips though, I didnt know that these targets were for bigger people. The reason why I want to loose some fat first is because I know full well I would have to pile on the protein and calories when I am serious with working on leaness and strength.

Your assumption here is completely untrue.  If you are eating the right kinds of protien and calories, you can add muscle mass/definition and maintain current weight or even lose weight.  

This gentlemen did The Rock challenge and increased his eating to roughly 5000 calories a day with appropriate workouts and was able to do this: (207 in the before and 208 in the after)

His blog can be found here:  http://rockingfor30days.com/the-rocking-for-30-days-challenge

In short, forget the crap that you are trying to justify to yourself about losing weight and focus on a healthy lifestyle that includes strength training and the rest will come along as you would want it.