Exercise Calories (Using Heart Rate Monitor and Garmin) - What proportion should you eat of them?

MikeBlake2 · May 2015

About six weeks ago, I treated myself to a Garmin that has a heart rate monitor, and I use both every time I go for a run - I then discovered that Garmin Connect app links up with My Fitness Pal, so as a result I now record what I eat.

I am training for my first ever 100km Ultra run in July and the training plan has me running four to five times a week, most of them 5-6 miles apart from the long run, which is upwards of 26 miles.

Today I ran 19 miles, and according to My Fitness Pal, I have an extra 3000 calories I could eat above my 1800 non-running day target. In reality I have eaten 2600 in total (so 800 of the 3000) and I am not hungry, so I will not be eating anymore today.
A six-mile run day gives me an extra 800 calories but again I tend to eat only 200-300 more calories on that day.

In short if I am hungry I will find something healthy(ish) to eat as an extra snack irrespective of whether it is a running day or not but it has crossed my mind on numerous occasions about how much I should trust these exercise calories - what proportion do people eat of them, and taking todays example, have I really burned 2200 more calories than I have eaten?

Hope this makes sense.

IsaackGMOON · May 2015

Eating around 50-75% of your burned calories through exercise is recommended.

TimothyFish · May 2015

I saw one marathon runner who said that he was burning 3300 to 3500 calories per day, while running 20-24 miles. So, I don't expect that 3000 extra calories is correct. The 2600 total seems closer to what he was eating. Keep in mind that the tools that estimate calorie burns give a number for the activity, but you are already accounting for your BMR. On top of that, a trained athlete is more efficient at an exercise than the average person, so you would burn fewer calories than the average person.

Asher_Ethan · May 2015

My understanding, when using a HRM, is that if you are doing an aerobic exercise constantly (running, biking, swimming, etc) and keeping your heart rate the same then the HRM is pretty accurate on calories burned. If you are not hungry then don't eat. When I have long runs and I use a HRM sometimes I can't eat all those calories either... But then the next day I'm EXTREMELY hungry.

brianpperkins · May 2015

http://www.runnersworld.com/weight-loss/how-many-calories-are-you-really-burning?page=single

That link provides a start point for looking at your net burn from running. One thing to remember is that most HRMs report total, not net, caloric burn.

If your goal is to run an ultra, you'll need to calculate what you're really burning so you can properly fuel. Failure to fuel requires sufficient fat stores to keep you going ... and if you exceed what your body can tap from those, lean body mass is the next place your body turns for fuel.

Francl27 · May 2015

You probably got to subtract your regular activity calories from that run though... so if it took you 5 hours to run that (I have no idea, just a totally random number), and your sedentary TDEE is 2400 for 24 hours, you'd have to remove 500 calories from that anyway, so you don't eat them twice (as that burn is already counted in MFP's calculations).

Other than that... I have no idea. But that's pretty amazing to run so much every day.

Brad592 · May 2015

FYI, the Garmin app doesn't count TDEE while a HRM is on.

MikeBlake2 · May 2015

Thanks for the responses - the Runners World article was interesting. Like Asher, I find the day after a long-run is when I will eat more than my allowance, and as stated before I will eat if hungry, so today for example I have eaten nearly 400 more calories than "allowed" but this is off-set by the massive amount of "spare" calories I did not eat yesterday. It feels like that so along as I do not starve myself, I am on the right track.

Exercise Calories (Using Heart Rate Monitor and Garmin) - What proportion should you eat of them?

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