Actually, you could gain weight with a feeding tube.
An example in burn pateints who need huge amounts of calories. The problem is that it's usually an NG tube which goes in your nose and down into your stomach. Probably ok if you're lying in bed trying to recover, but might be hard to train with. For sure you'd get some weird looks LOL!
I used to know a national champian power lifter . He claimed that his wife was and RN and that she use to hook him up to IVs and he would boat load aminos and other nutriants the were made for burn patients. He claimed he would train and then hook up the IVs and just veg in front of the tv all day[take in 10000 to 12000 cal a day]. He said he got freaky big and strong from this. He competed in the Worlds Strongest man on two different occasions .[ he used to work for me] Crystal meth was his downfall. The guy was sick strong when it came to pulling and hand strength. I wonder if it was true . But the concept sure makes sense.......it would be nice not to have to eat so much food . He also said he never felt bloated or had stomach problems from this . Only tired from body having to assimulate so much......I wonder? He said he learned this from a friend of Rory Leidimeyer [ great physique .....could given Haney a go back in the day if he ever got it together.....and one strong fucker to boot...]
The only type of feeding tube that I ever saw I wouldn't want. My dad had one that ran through his abdomain and into his stomach. Not vary pleasant to see and I know he wasn't comfortable.
So far I have found no studies that suggest this type of feeding is more efficient than just eating or drinking but maybe no one has looked into it much or published any work on this topic because they thought only athletes would be interested in the comparison?