Calories!

KayTheGemini

How would my calorie deficit help me lose weight?

rileysowner

By having the calories you need for the day but don't eat (that is the deficit) used for fat stores instead. Without a calorie deficit a person will not lose weight.

bajoyba

You can't lose weight without a calorie deficit.

Your body needs a certain amount of calories to maintain its current weight based on a variety of factors (weight, height, lean body mass, activity level, etc). If you eat more than those maintenance calories, you will gain weight. If you eat less than those maintenance calories, you will create a deficit and lose weight.

You can plug in all of your info and goals into MFP and let it calculate a calorie goal for you (and eat back your exercise calories), or you can do some research on your own to determine your maintenance calories (also known as your TDEE (total daily energy expenditure)) and how many calories you should eat to lose weight.

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

and/or this: http://www.myfitnesspal.com/topics/show/912920-in-place-of-a-road-map-3-2013

It will take a few minutes to get through that reading, but it's worth it. If you take that information and apply it appropriately, it will take you a long way.