Losing weight on an exercise bike is certainly possible but you have to really pedal hard to break out in a sweat to achieve a good desired result in weight loss.
I've pedaled a stationary exercise bike daily for 40 minutes at 20 minutes each time throughout the day and after 2 years I dropped 40 lbs of weight which is all I needed to lose so it's possible.
Getting out and walking or jogging can help you lose even more weight and help strengthen your heart to keep you healthy and prevent diabetes, heart disease and strokes along with losing the weight.
I always walk somewhere when It's not too far or the weather isn't too bad because the more I walk the better health I'm in.