Losing some weight depends on a number of factors. One basic factor is the amount of calories you're taking in compared to the no of calories you burn. So, it depends on the second meal you eat and how many calories that contains to get an estimate of your daily intake. Knowing how much calories you burn is a bit more complex, you can get an estimate through several online calculators. Comparing both numbers gives you some basic insight.
There are many more factors important as well; level and type of exercise in the gym, the type of nutrients you eat, how much weight you want to lose, etc.
To be short; it's hard (if not impossible) to give a good answer based on your question. Feel free to email us if you need more information.