How acurate are the numbers for calories burned?

fancyface1955

Hi All!

So just about everyday i'm supposedly not eating enough. I enter my workouts and the amount of time spent on them and some magical little number pops up. I know I should get an heart monitor to better track it. But i'm curious to know how accurate these numbers are. Today for example I went jogging and later on I did my Insanity workout. When I plugged that info into my diary it came up with 700 calories burned.
I've added all my food for the day and have eaten just a little more than that. Should I continue to eat more food or just eat my normal 1200. I've seen other people post that they don't eat back their calories burned- but just about the end of each day it says i'm not eating enough and will fall into starvation mode.
Anyway my question is how accurate are the numbers they came up with for calories burned??
Thanks :-)

SugaryLynx

They're not accurate, but you're eating the bare minimum, so even if burn half of that at 350, that's still a net of 850 if you eat nothing back. While starvation mode as it's tossed around isn't a thing (there is still adaptive thermogenesis but that happens over a great length of time), you still need to fuel your training. So, I would make sure you're accurately tracking 100%, weigh and measure all the food you can and see how you feel. I, personally, couldn't stick to 1200 calories net. I ended up doing 1650 net for most of my weight loss but if you do decide to, I would make sure you're eating at least half of your calories back, if not 75%. The burns for exercises vary a bunch from person to person.

Edited to add: this is a great read

http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants

jonnythan

Even 1200 calories is ridiculously low for anyone but a very small, sedentary person. Eat back your exercise calories.

The 1000 a day you're eating is not enough. You're leaving 200-500 on the table BELOW the 500-1000 already built into your calorie target. You are running calorie deficits that are too large.

stumblinthrulife

To answer the titular question - not very when used unmodified with MFP. Most calorie estimates are gross. Since your base activity level is already factored into the MFP calorie count, you should be logging the net burn. Depending how active you set your base level, you should deduct between 2-4 calories per minute from the total, because MFP already gave you them before you even set foot in the gym. This is even true for HRMs.

I found that when I started out, the error didn't make much difference. My workouts were too short for the gross v. net error to have a big impact. However, as I ramped up my training, the error became large enough to completely eliminate my deficit. I now manually reduce my burns by 2 Calories per minute (the amount I burn sitting doing office work - my default state).

To echo the sentiments of others, don't just eat 1200 Calories total in a day. That's crazy. Eat at least 1200 Calories plus your exercise. Extreme deficits lead to negative effects on body composition. Eat too little and you don't just lose fat, you lose lean mass too. Your body can't take it all from fat fast enough to keep up with demand and it starts burning everything else too. Especially if you don't have a good strength training program in play. It's better to lose 1 lb of fat a week than 1.25lb of fat and 0.75lb of lean mass. Even though the scale may be moving faster, you won't be happy with the end result.

ottermotorcycle

Here's the thing:
1. MFP calorie estimates are NOT, generally, accurate. They usually overestimate.
2. If you are eating at 1200 calories a day, which I do not recommend, you MUST eat back your exercise calories.

Kay, a few more things:
Find out what your BMR is (you can search for a BMR calculator online) and use that as your baseline. If this is above 1200 calories, you're going to have to increase your calorie intake. BMR is a fancy little number that tells you how many calories your body needs to keep your organs functioning, and it is below this number that you face the possibility of metabolic damage.

You can use your BMR, multiplied by an activity multiplier ranging from 1.0 (in a literal coma) to 2.0 (dedicated athlete), to calculate your TDEE.
TDEE is a better system if you are doing a program like Insanity regularly. In that case you should change your activity level to something higher and not count back the exercise that you have accounted for in your activity level (if you were to do additional exercise, add that in.)

Also, if you're going jogging, find out how far you went and how long it took you to get the most accurate number. You can use a GPS-based app like RunKeeper or you can log it into Google Maps or something when you get home.