What is the best way to gain weight?

If you want to add some muscle, you might see your times slow down a little.  It's a choice to have to make based on your personal priorities.

You do want to make sure that you do not slip into a caloric hole as that will have an impact on both speed and endurance.

The simple answer to your question is to increase your caloric intake.  A more complex answer is how many calories.  This is a simple matter of determining your caloric burn rate vs. calories taken in.

I learned my caloric burn rate from getting my VO2max test done.  This is not the only method available. 

Perhaps some others can guide you on how to obtain your resting metabolic rate and your exercise metabolic rate (e.g. how many calories you burned based upon exertion levels)?

No disrespect, but I think hate you.

x2     

Before I started training for IMFL, I went to see a nutritionist, and she said to put on some weight first.  I told her what a typical training week looked like, and based on my size, age, etc she basically told me how much to eat and what type of calorie distribution to look for (% fat, carb, pro). 

I really had to monitor how much I ate, and I had to go out of my way to eat more than usual.  I would eat a meal that would satisfy me, then figure out how many calories were in it, then go back to the fridge or cupboard to find more calories.  It was kind of a pain. 

Easy way:  see a nutritionist and let them figure it out for you
Hard way:  read up on everything yourself to figure out what you should be getting

I ended up gaining about 5 pounds of muscle.  If you're really training for triathlon, the weight you gain will be muscle and not fat, so don't worry about that.  Seriously, though, even muscle mass will slow you down a little when it comes to endurance sports, so I would say don't bother putting on the weight.

Just want to say that I am in the same boat, I'm about 6'1" and after losing 20, Im down to 170.  I  have to say that I don't know how much more big ol' peanut butter sandwiches I can handle but I am struggling to not lose any additional weight.

 The reason I am posting is that I believe its possible to stay "skinny" and still look good... You really need to watch your calories and eat alot of different stuff so that you look healthy skinny(Lance?) and not malnourished(random anguished rock and roller).  Increasing caloric intake could definitely increase your overall perfomance.

 Anyways, just my uneducated 2 cents. 

Unless you have a very (as in, abnormally) large frame, 165 is not 'skinny', in the sense of 'unhealthy'.  Check out any of the myriad charts of 'ideal weight ranges' and even for 'large framed' 6 foot men you'll see that 165 is in the range.

Sometimes it just takes others a while to get used to the new you.  I went through this in a strange way.  I used to be very skinny (from running).  Then I had a series of operations, which led to disgusting self-pity, which led to inactivity, which led to pounds.  I gained probably 30 pounds.  I was in that shape for about 18 months then snapped out of it, and now I'm back down below 145 (I am 5'8", getting back close to the 140 I used to be.  My wife loves it.  My mother thinks that I'm 'too skinny', and lobbies for me to eat pancakes and pierogies every time I see her -- despite the fact that I weigh slightly more than I did 3 years ago.  She got used to a certain size (170pound) me, and now that I'm smaller, she thinks I look 'unhealthy'.

Now, if your wife just wants you to have more muscle, that's a different story.  If you're inclined to follow her wishes here, there are tons of decent resources out there for how to gain weight without gaining much fat.  Consulting a nutritionist, as someone suggested, is not a bad idea -- a good one will help you gain the muscle without gaining fat.  You will probably slow down as a result, though, assuming that your body fat is already low.

X3 The best method I have found is eat more exercise less and supplement with Beer.  You WILL gain weight!

After I got out of High School as a cross-country runner, I weighed 151 lbs (6' .5"  Incollege, I kept up with running but thought I was too thin.  I started lifted weights and put on muscle and got up to 165 lbs  over the course of 4-5 years.  That was 25 years ago.   I ended up at 203 lbs at my max (after an anniversary cruise), and hovered around 195 for several years.  After tri training for 5 months, I'm down to 181 and want to get down 170-175.

 Summary:

1. The heavier you are the slower you will go (generaly speaking).
2. The heavier you are, the more stress you will put on your joints.
3. As my coach used to say "the lean hungry dog wins the race."

x4

I've got a 'sure-fire' way to gain a tonne of weight - have four kids, and eat lots of crap LOL!  Worked for me

Wish I had your problem....after losing about 75-80 pounds I have plateaud big time....can't seem to get below 140-145 (want to be 130)....and the more I train the harder it is!

6 feet and 165 is definitely not skinny!  Your body mass index index (BMI) is 22.4, which puts you smack in the middle of normal (18.5 to 24.9).

In the last 10 years we've gotten so used to seeing so many hefty and overweight people that normal weight people are now perceived as too skinny!

If you want to gain muscle masss, start a lifting program with appropriate nutrition.  Debatable if it will make you faster at triathlon, though...

Brian

X5

I don't agree entirely with this.  It really depends on what your mass is made up of.  13 years ago I lost 30 lbs really fast.  I was eating only carbs (didn't know better), and running a lot.  I got down to 160 and am 5'10".  10% BF.  My biceps measured 12in.  I looked emaciated and people thought I was dying.  I did not look healthy to anyone...and this had little to do with social norms.  I had lost a lot of muscle because I hadn't eaten the right combination of food.  175 is a much safer weight for me.  (now if I could only get to that weight again).

The true trick you are looking for is to add muscle mass and not gain fat.  Lifting weights and eating more lean protein may help with this.  I am sure there are others with better info than me. 

I was gonna say just eat lots of donuts.  Works for me.

... but I was trying to lose weight.  Donuts didn't work too well for that.  Just be patient, really.  The holidays are coming...

 Why?