My search of this turned up nothing but threads on how to loose weight. My problem is just the opposite... I want to gain weight.
I am 6' 0" and weigh about 160
I am 55 and have weighed this ammount since high school. I am just one week into the program and looking for any tips on gaining weight.
I would like to put on 20 pounds
I have a good diet and can eat any thing or ammount I want and just don't gain weight.
Quite obviously it is a genitic thing but my family is not a bunch of tall skinny people.
What can I do???

Uh just follow the nutrition plan. If you want to add on weight/msucle up which level you are in. I believe 160 is level 1? Just work at lvl 2 or high lvl 2 etc.

Bear

Try this calculation:

66 + (6.23 x weight) + (1.7 x height in inches) - (6.8 x age) = ?

Next....find your level of activity:

1.2 for sedentary
1.375 lightly active--light workouts 1-3 times a week
1.55 moderate--moderate workouts 3-5 times a week
1.7 very active--hard exercise 6-7 days a week
1.9 extreme--hard daily work outs or a very physical job.

P90x would fall in the 1.55 I believe.

Multiply your ? number by your activity level number.

Now...to lose weight subtract 500 calories or so from this.

To maintain just keep the same amount of calories

To gain add 200-300 calories per day to this number.

so for you---

66+ (996.8) + (914.4) - (374) = 1603.2

1603.2 x 1.55 = 2484.96

2484.96 + 300 = 2784.96 calories a day. Say 2800/5 = 560 calories a meal 5 times a day. Try that for a few weeks or so, just keep upping the calories by 200-300 until you start to gain weight.

Get quality calories and not just junk food. Junk food is usually empty calories that will do more harm than good. Adding muscle will add weight to you. Try creatin also....5 grams before workout and 5 grams after your workout. Also taking Casein protein at night before bed with a tablespoon or 2 of flax seed oil would be good also.

I don't claim to be certified or a specialist....just an advt reader of a lot of different books. I'm sure you'll get a range of responses. Use what works.

Heres a good place to buy your casein protein.
http://www.muscleandstrength.com/store/100-casein-protein.html#product-description

You'll need to consume more calories than you burn. Like the others said, find your calorie maintenance mark, and eat about 500 calories over that each day. That way you'll be gaining about a pound a week.

The P90X may not be the best program for you either if you're trying to gain a lot of weight. With the long and intense workouts and all the cardio it can be difficult to add a lot of mass and recovery time is not always optimal. I would personally look into a program that has you lifting heavy on the core lifts like squats, bench press, deadlift, etc.

It is up to you though, and the P90X can still put some muscle on you. It will also improve your health and your overall condition.

many thanks for the replys. I do understand that I need to take in more calories than I burn, but keeping track of everything I eat seems to be such a chore. I guess I'm more into the working out part.
I was hoping to hear some tell me to add some suppliments, like protein, might help.
Do you think that might help or just be a waste of money?

Diet, I repeat...Diet is just as important as your workout for whatever your goal is. Keeping track of everything is a chore and so is eating several times a day. Once you enjoy it and keep your mind focused on your goals then it's not so much a choir.

If you are looking for supplements, then please remember the definition of the word. Supplements are not your diet, they aren't the magical answer. They only enhance your diet and workouts and they do it slowly at that. Anything you buy, yes....will be a waste of money until you treat your diet as an equal to your workout.

However, there are always steroids...but then again you will have to have a proper diet even with those. There is no getting around "diet" and there are no shortcuts. Sorry.

Thanks Rodney.... I guess I didn't realize the importance of diet

Rodney is exactly right. You will still need to eat more than you burn if you want to gain weight and muscle. If you don't eat more calories, you won't gain weight, which in turn leads to only slight muslce gain.

It won't matter a whole lot if you take a bunch of supplements and protein if you're not eating enough. It can be a chore at first to track what you're eating, but after a little while it becomes pretty easy.

Beer, lots and lots of beer!

Not trying to push any buttons here but p90x is designed to get you ripped and lean.If you wanna gain weight and have a really high metabolism possibly a traditional bodybuilding program would work better?Not saying you can't gain mass on p90x but it would require a buttload of food lol.If you wanna get ripped and be a fit dude then do the program!!