Going on vacation for 3 weeks... Afraid I'm going to gain

Unfortunately when you lose a good deal of weight while doing low carb, then you do a period of time where your carbs are moderate to high (vacation) you will indeed gain weight. Most of it is in the form of glycogen and water, not fat. To gain fat you must eat more calories per day then you burn (around 3500 more to gain a lb of fat). Fortunately, after the vacation ends, you'll eventually drop the water weight and the only real weight gains you'll be left with are the ones from eating over the amount you burn. There is no real way to "rev the metabolism". You can slowly up calories to maintenance which might help a bit. You could also slowly reintroduce carbs so the water weight gain isn't as dramatic. Unfortunately at the end of the day its calories in vs calories out whether low carbing at home or enjoying yourself on vacation. I personally still workout on vacation because I enjoy it. That helps a bit with calorie burning. I also usually eat only 1-2 big meals on vacation and try and keeping snacking to a minimum.

I don't know where you're going, but you can make it work. We have a kid who has real severe food restrictions for a health issue, and we wanted to drive across America. You know just once with them, see the grand canyon, go to New Orleans. We drove from Whole Foods to Whole Foods, had fabulous steaks in Texas, and Jambalaya and Etoufee in New Orleans. Yes we ate Beignets, only once with cocoa. But otherwise, you know Salad bars, fish, there's always something on a menu. "No bread basket, Can they cook it without Fat, What's under 500 calories, You got a fruit plate" You can do it. Enjoy. Buy some new clothes if you're down two sizes have fun. :flowerforyou: