"beer belly" is a loose term.
It's not because you drink beer that you have a belly.
It's because your intake of food/drinks is higher than you require it in order to maintain your current weight.
By spending more energy than you eat, you will lose this belly.
Nutrition and exercise. I would start with nutrition as it is the most important of the two.
As stated above, any extra weight on your body is an unneeded stress that your heart gets which increases health problems.
The more your heart is stressed the more it beats.
Take someone whos heart beats 60BPM and one who beats 90BPM.
minute/hour/day/year
60/3600/86400/31536000
90/5400/129600/47304000
That's a lot of mileage you could save on your heart.
I understand you work from 1PM to 10PM...but you will have to MAKE time to get this problem solved.
Now drop down and gimme 20.
For you to have a proper calorie intake everything must be considered.
Height/Weight/Age and the level of activity at work and in your personal life.
With this info you can obtain the calories you need in order to maintain your current weight. Subtract 20% from this amount and you got yourself a proper calorie deficit to reach your goal.
After this...you should implement a decent workout routine (which you will stick to!) and voila. This method is not 100% accurate but it is a good base to start from.
I would do a full body workouts 3 times per week with cardio on the same days...active rests on days off and keep it easy on week-ends.
Hope this helped
Eric