For all you nutrition/fitness experts out there.... ;)

MFP builds in a deficit regardless of exercise. When you use more energy, MFP gives you the ability to eat more because otherwise you might make that caloric deficit too large...and in the long run, that will sabotage your progress.

Search it in the forum... this question probably has 100 posts that discuss it.

Eat your exercise calories. There are so many great articles why, and everybody is asking if they should or not. EAT THEM. You WILL lose weight.

It's to help you properly fuel your body for it's needs. By breathing, walking to an from your car, being, you burn calories and inorder to fuel your body so that it's efficient it needs to depend on a certain amount of calories. When you exercise you are burning more calories so your body needs more calories to function properly and efficiently.

Edit: if you don't have enough calories to fuel your body consistently your body will adjust and your metabolism will slow to compensate for the lack of nutrients and calories. You also may find, over the longer term, that you don't have the energy to perform during work outs (been there, done that, in a past life), or start getting light headed.

Let's say for the sake of easy math that your normal calorie allowance is 1,500 calories and you weight loss goal is 1 pound a week. That means that (according to MFP) that you would burn 2,000 calories just sitting on the couch all day. The 500 calories deficit would give you a 3,500 calorie deficit after 7 days, and that is how much of a deficit you need to lose 1 pound.

Now, let's add the exercise. Assume you burn 500 calories doing cardio today. That means that you burned 2,500 calories instead of 2,000. Now if you stick to the 1,500 calorie allowance, your deficit is now 1,000 calories instead of 500. However, look at it from the other direction: it also means that you only took in a net of 1,000 calories, which is below the recommended minimum of 1,200 to prevent "starvation" mode. I think it is safe to ignore some of your workout calories because it's easy to overestimate how much you burned and to underestimate how much you eat, but don't ignore them all, or you will sabotage yourself.

It sounds tempting at first to ignore your workout calories to speed up the process, but that's the point of this site- to help you build healthy habits, not to bring you back to your high school weight in a month. I've been on those types of diets and all the weight came back. Slow and steady, that's what you have to keep in mind. Besides, it gives you great incentive to work out longer and harder. Burn more, eat more.

I eat back half my exercise calories that I burn so that I still have room if the computer underestimates my calories burned or if I don't calculate them the right way throughout the day. It's something you will have to experiment with because some people eat back all of their exercise calories and don't lose weight and some do. It's all how your body responds to your change in eating and exercise habits. So far it's working for me! Also, by eating back some of your exercise calories you aren't so hungry. For me, 1200 calories is very easy to eat, so if I workout and burn 400 calories, I get an extra 200 calories more that I allow myself since I love eating rather than not exercising and not getting those calories to eat.

I went low yesterday, I ate 1,879 cals, the goal was 2,885 as I'd burned off 1,375 using a HRM in the gym - and I ended up under by 1,006 cals.

Today I woke up one pound something heavier than the previous day. I also felt hungry all day, grumpy and light headed - I think it's best to eat them back or at least try to eat most of them back xx