So up until July 1st, I weighed 170 lbs even, which was 19 lbs less than what i weighed 6 months prior. I've lifted for around 4 years and those last 6 months before July I wasn't eating enough and was just focused on other stuff and got off track, so I went from 189 to 170 and lost a significant amount of strength.
Then I decided that's enough of this shit, time to get back on track... So on June 30th I went out n' bought nearly 3 months supply of food that I'd need, and started on the 1st. Since then (31 days later) I've gained 9-10 lbs back already and my strength has shot up significantly. ya hear about "muscle memory" but it's great to experience it first hand.
I put up more than I ever have today on dumbbell military press (85x7 unassisted w/ nearly full ROM -range of motion-) and I still have 10/15 lbs to go

The goal is to be putting up 100's by this time next year.
If anyone is interested in what I've been eating:
1. Oatmeal w/ OJ + MultiVitamin
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2. Apple slices dipped w/ peanut butter
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3. 1 can of TunaFish + PB&J Sandwich
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[lifting]
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4. 1 Egg Protein Shake
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5. 2 Chicken Strips w/ Misc. Carbs
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6. PB&J Sandwich w/ Carrots
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7. MISC. MEAL (preferably a bigger meal)
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8. 1 Can of Tuna
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9. 1 Chicken Breast (around 45g of protein)
+ PB&J Sandwich
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I love PB&J sandwiches, in case ya didn't notice. If I start to try n' cut I will cut down on those significantly. The dash signifies a meal, time inbetween is usually around an hour to 2 hours. I will probably be able to gain 10 to 15 more pounds on this until I plateau, in which case I will need to start eating more food.
Anyhow just thought I'd share for those of you who find it difficult to build mass. Just follow a diet like that with a lot of hard resistance training (freeweights) and you'll build up muscle / weight in no time, especially if you've never routinely lifted weights before.