if (player_mc.hitTest(food)) {
	var_score = _parent.score.text;
	var_score++;
	if (var_score>8) {
		//First pass-> var_score=9 -> var_level is still = 0 I guess, so level.text =0 and var_level now = 1
		//Second pass-> var_score=10 -> var_level = 1 so lvel.text =1 and var_level becomes 2
		//Third pass-> score 11 level goes to 2 and var_level to 3..
		_parent.level.text = var_level++;
	}
	_parent.score.text = var_score;
	_parent.stage.food._x = 500;
	_parent.stage.food._y = randRange(0, 290);
}

FIXED:

add this on the top of everything: 

var levelStep:Number = 10;

and here's the fix

if (player_mc.hitTest(food)) {
	var_score = _parent.score.text;
	var_score++;
	if (Math.round(var_score/levelStep)==var_score/levelStep) {
		var_level++;		
		_parent.level.text = var_level;
	}
	_parent.score.text = var_score;
	_parent.stage.food._x = 500;
	_parent.stage.food._y = randRange(0, 290);
}