How do I use MFP with Garmin Express and vivoActive properly?

Hello everyone,

I just started using my vivoActive and synced it up with MFP. I pretty healthy in general and exercise a good bit, but I put on weight over the winter that I want to lose. I've normally maintained my weight very steadily without having to obsess over calories or anything so I'm not exactly a weight loss or nutrition expert.

I put in my weight, target weight less goals, and everything else in MFP and my Garmin Express profile. I have been logging all of my workouts with a heart rate monitor and syncing up my daily steps every day, and I have been adding every single thing I eat or drink into MFP as accurately as possible. Now I want to make sure I am using these tools together properly.

MFP gives me the basic recommendations for calorie/carb/protein/sodium/sugar intake, and it accounts for activities that I logged with the heart rate monitor. It does not seem to account for calories that Garmin estimated that I burned based on my daily steps and walking distance. I have usually been going 400-500 calories under the MFP recommendations, significantly under on carbs, at or over on protein, about even on sodium, and a good bit under on sugar. When I sync MFP up with Garmin Express, the Garmin Express Calories In/Out screen properly logs my calorie intake and shows calories burned through activities and walking, but the net calorie goal is a good bit higher than my MFP recommendations. Which parts of each tool should I be using? Should I factor Garmin's step calories into MFP's calorie recommendations and then use MFP for the rest of the nutrition plan? Is it ok that I am going 400-500 under on calories and then going lower on carbs and higher on protein? I'm a 28 year old male, 5'6", and about 160, and I am pretty active so I figured it would be ok to go higher on protein to keep muscle mass, but I'm not an expert.

Anyway, sorry for the long post. Any advice or recommendations would be most welcome. Thanks!

-Chris