For 3 yrs drank coffee all day and only ate dinner. Eating again and gained 40 lbs in 5 mos. How do I lose weight on one meal a day?

You have probably screwed up your metabolism because of your years of starving yourself. Your body will take some time to become used to getting food again and you will soon start losing weight providing you are not eating too much.

Make sure you follow a healthy diet, and eat regularly.