How to gain weight?

Question
My significant other has lost a lot of weight.. he is about 135lbs and 5'9. He wants to gain weight but is having trouble doing so. His diet has not changed since the weight has dropped and althouh it may sound unhealthy, I encourage to load up on calorie dense foods such as butter, avacado, etc. Do you have anymore advice as to how to help him gain weight -- would exercising be "bad"? And if he can't explain his weight loss, do you think he should consult a doctor to make sure nothing is wrong? Thanks.
P.S. I was the one who asked about my dad's little "bet", and you were so helpful I thought I would ask about this, too. Thanks!

Answer
You should ABSOLUTELY have him see a doctor. 135 pounds at 5'9 doesn't sound too bad though. At my lowest weight a few years ago, I would 180 and I'm 6'0 (well, 5'11 3/4). I am NOT a doctor, but if he has lost a lot of weight in a short period of time, and it's NOT from busting his ass on the treadmill (or any other kind of strenuous workout) then yes, have him see a doctor and get some blood work done.

Now, assuming he IS healthy and he wants to pack on some pounds, I would suggest a diet in calorie-dense foods BUT make sure they're healthy foods. You mentioned butter... it's loaded with saturated (BAD) fat. Make sure you stick to fats that are high in UNsaturated fats (avocados are good, also nuts, olive oil, and most fish). There's a whole page on my web site dedicated to fats:

http://ricksweightloss.com/diet/foodtypes/fats.asp

He should also eat a lot of protein and healthy carbohydrates. There's nothing better than a steak or a bowl of whole-grain pasta (I like buckwheat noodles) when trying to pack on some pounds.

Now, YES, he should definitely exercise... but instead of cardio, he should focus on weight training. This way, you're putting all of those calories to good use. Instead of storing them as body fat, if you're pressing the irons, your body will convert those calories to MUSCLE, which I'm sure he'd love... and you'll love.

Hope this helps.

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