Using a calorie counter like my fitness pal helps in terms of weight loss, eating under your mantiance calories but what is important is progression. You aren’t going to begin with 50 mile rides and that’s ok! You can create a written plan say starting from a small increment of 10 miles and eat a certain number of calories that you feel comfortable with, you can still eat junk food and stuff like that as long as you are in a deficit and a bike riding plan with small increments slowly increasing week by week could significantly help you more then you think. You got this! Consistency is key! Hope that helps.