Nice game. I encountered 2 issues: fixing them should probably help you make the game a bit better.
Firstly, when starting a new game, I didn't realize I had to run forward and got a 'you lose' message immediately. You can fix it by starting the timer only when player presses some keys.
Secondly, I encountered a bridge with maximum target weight lower than my current weight. I don't know if it's possible to actually lose weight in this game. Maybe it's a glitch with weight calculation.