Most Europeans do not bike daily. Most drive cars where they need to go. You are not losing 5 to 10 pounds in 10 days (unless you are dehydrating yourself). 5 pounds would be a 17,500 calorie deficit or 1,750 per day. The base metabolism for a male is around 1800 calories. That means that you'd be eating 1/10th of a banana every day to get that type of loss. For me a century bike ride (100 miles with 5,000ft of climbing) consumes about 2,900 calories. Are you doing century bike rides every day while only eating 1,200 calories while in Europe?

Math checks out.

I'm someone whose weight easily oscillates by 2kg (1kg up/down from my average trend line), and it took a while to accept only the trend line over several weeks matters.