I am the classic "hardgainer" - tall and skinny with a high metabolism, losing weight is a default state for me.  I have to consciously watch my diet to maintain weight, and take some pretty extreme actions to gain any.  Over the past three years, since I got serious about fitness, I've made several serious attempts to gain muscle mass - most of them have failed.

A few months ago, I tried again with a 12-week strength cycle that was my most successful venture yet:  I put on 16 pounds, about 8-10 pounds of which was muscle.  For those of you interested in putting on some muscle, I will share what I've learned.  None of this is a secret:  it's all freely available out there on the internet.  But it takes some experimentation to separate the wheat from the chaff, and then you actually have to DO it, which is the hard part.

I should point out that gaining MUSCLE and gaining STRENGTH are not necessarily the same thing.  Plain Vanilla CrossFit is actually quite good for gaining strength, but is not likely to add a lot of muscle to your frame if you're naturally skinny.  How does this work?  Well, when you flex a muscle to move a weight, you're not using anywhere near all of your muscle fibers to accomplish this task.  Regular training will train your Central Nervous System (CNS) to recruit more fibers from the muscles you already have, which will make you stronger without actually adding any bulk.  If you're a climber or otherwise averse to additional mass (muscle or otherwise), this can be great, but there are diminishing returns - you'll never get to 100% recruitment, and at some point you will need to add more fibers to continue to make gains.

Just like losing weight is a hormonal event, so is gaining muscle.  Your primary job is hormone manipulation:  stimulating the ones you want (hGH, Testosterone) while keeping the detrimental ones (insulin, cortisol) at bay.  There are essentially two places you need to make changes to make this work:  the kitchen and the gym.  I'll cover them separately.

The Kitchen

Not surprisingly, the most important thing you have to do is EAT.  A lot.  Way more than you think you should be eating.  More than seems reasonable, or maybe even safe.  You see, while you CAN get stronger without getting bigger (see above), you cannot gain MASS without a regular caloric surplus.  It takes a lot of energy to make new muscle fibers, and unless you're a teenager your body is reluctant to make that investment.  You need to convince it that it is flush with resources, and can afford new cells.

Living in caloric surplus, some amount of fat gain is inevitable.  Sorry.  You'll just have to lose it later.  Body builders refer to the cycles of gain and loss as "bulking" and "cutting," and wil frequently do what's called an "uncontrolled bulk," where they simply devour everything in sight, with no regard to macronutrient ratios or quality or caloric content.  Easy, but lazy, and can have some disastrous consequences on your performance when you gain 3 pounds of fat for every pound of muscle.

Better, in my opinion, to do a "controlled bulk" - where you ride the edge of just enough caloric surplus to put your body in growth mode, but keep fat gain to a minimum.  It's difficult to do, but your friends won't start calling you "Chubs" and you'll still be able to do a pullup.  Here are some tips:

• If you know your BMR (Basal Metabolic Rate - the amount of calories you need to take in each day to roughly balance the amount you burn), aim for at least 500 calories above this.  Shoot for between a half-pound to a pound of weight gain per week - any more than that and you're piling on too much fat.
• Keep the carbs low, and low GI on the carbs you do eat - insulin spikes will just deposit all the energy you take in as fat.  I would aim for no more than 200g/day of carbs, on average.
• This leaves protein and fat.  Consume mass quantities of these.  Animal protein is far superior to vegetable protein in terms of bioavailability, and the most efficient source of protein (both in terms of bioavailability and price per gram) is the egg.  Omelets, frittatas, scrambled eggs etc are all your friends.  I would make meals out of nothing but rotisserie chicken, slices of cheese and nuts.
  
• A common technique, particularly among CrossFitters, is GOMAD (Gallon of Milk a Day).  This is a great way to add a couple thousand calories to your daily regimen without too much fuss or expense.  The only downside is that you have to actually drink a gallon of the stuff each day, which can be intimidating.  If you go this route, the milk should be whole and organic, and you should be under 25 years old - over that and you're likely to get chubby from all the carbs.  This technique is really designed more for Matthew and Jonathan than to the older among us.  I went with QOKAD (Quart of Kefir a Day) instead, and it served me very well.
• Keep food quality HIGH.  You don't want to be pumping chemicals into your bloodstream in large quantities, as your body will just have to filter it all out - and you want it focused on one task.  Eat your veggies with plenty of olive oil and butter, and avoid packaged foods, artificial sweeteners, and anything that comes in a tub with a picture of a ripped athlete on it.  That isn't food.
• Which brings me to supplementation.  Normally I avoid it, but in this case I did have a spoonful of Creatine Monohydrate a day (mixed in my kefir).  It's cheap, been around for ages, and has proven results.  It will cause you to retain more water, though.
• Stop eating 2 hours before you go to bed.  Large meals of any variety (high carb, protein or fat) have been shown to diminish the body's growth hormone response.  Human Growth Hormone (hGH) is the single most important chemical in this endeavor, and you really want to maximize it.  The body releases hGH in waves throughout the day, but by FAR the greatest release occurs in the first two hours of sleep.  Getting to sleep earlier (ie, before 10) also increases hGH release.
• For this reason, be VERY conscious of your sleep.  Get at least 8 hours a night, in a dark room, early and relatively fasted.

The Gym

One of the things that makes CrossFit so great is its adaptibility.  With just a little tweaking, you can keep CrossFitting while still focusing on gaining strength and muscle.  The goal here is, again, hormonal manipulation:  you need to send the message to the body that it really does not have sufficient resources to do what is being required of it.  The most effective way to do this is to lift VERY heavy weights in movements that stimulate the largest number of muscle fibers.  Typically, the two movements that are acknowledged to provoke the greatest CNS response are the Deadlift and the Squat.  (I just read an article last week that quoted Charles Poliquin as saying the Snatch-grip Deadlift off a 4" box is the single greatest muscle-building exercise that exists).  There are a couple ways to go about this.

• The most straightforward is probably Max's Simple 3x5 routine for CrossFitters, which he first wrote about ages ago.  Set aside two days a week just for lifting, and do Deadlifts and Squats with a couple smaller complementary movements (ie, Press and Bench Press), and then just go up 5 pounds every week until you can't go up anymore.  People have been doing essentially this routine for decades, and it is tried and true.
• There's been a lot of fuss lately about CrossFit Strength Bias (CFSB), which is an adaptation of regular CF WODs to promote greater strength gain.  It's gotten good reviews, but would essentially prevent you from training with CFEB while you were doing it, which would make us all very sad. 
• CF Norcal promotes Max-Effort Black Box (MEBB), and they proved its efficacy with their showing at the Games.
• In MY latest cycle, I went with a hybrid of CFSB and the 3x5 routine.  It was quite challenging, but wound up putting 30 pounds on my squat and 40 pounds on my deadlift, which I was very happy with.  If you have any questions about this routine, fire away.
  
• You'll notice the common denominator of all of these plans is that they have heavy weights, short rep schemes, and full-body movements.  Whatever you wind up doing, make sure you have these elements in place.
• Avoid high-volume.  Regular metcons are great, but try to keep your workouts under 45 minutes, and don't do any long-distance running/cycling/etc.  Long workouts will spike your cortisol and can actually be catabolic (ie, burning muscle for energy), and will send the message to your body that now might not be a good time to add more mass.

More info

I found these articles to be particularly helpful when I was figuring things out for myself.  If you're serious about putting on some muscle mass, I highly recommend reading all of them through.

• How to Build Sleeve-ripping Arms by Working out your LEGS?!
• How to Gain Weight and Build Muscle
  
• Building Muscle 101
• Hardgainer No More

WOD 090729

AMRAP* in 20 minutes:

5 C2B Pull-Ups
5 Handstand Push-Ups

Post number of rounds completed to comments.

*As Many Rounds As Possible