Would I lose weight IF...?

Losing weight is a function of calories in/calories out. If you burn more than you consume, you'll lose weight. If you bike 40 minutes a day (vigorously), and restrict your total calorie intake, you'll reduce. Write down everything you eat - keep a food diary and tally up the calories you eat. Vigorous bike riding will burn @12-14 calories per minute in addition to what your normal metabolism is. While the general rule of thumb is that a pound is about 3500 calories, the most recent research suggests that's not an absolute measure. Use it as a rule of thumb. Do some web research to figure out your basal metabolic rate (probably in the 2000 calorie/day range at rest). Add in what you eat, subtract what your able to burn with exercise and you can figure out how long it should take to take off some weight. Good luck!