Find out your TDEE. Use this –
Eat 15-20% less than this figure in calories (eg 2000 calories a day, eat between 1600 and 1700 calories a day).
Make sure your protein level is between 1g per lb and 1.5g per lb of bodyweight to hold mass (eg at 200lb 200-300g protein).
Lift weights several times a week to give your body a reason to hold muscle.
Cardio, start with 3-4 sessions of 20 minutes or so a day per week, and increase this when fat loss slows to 5-6 days a week. Or add 5 mins extra to each session.
Finally, reduce your intake 100-150 calories when fat loss stops to keep fat burning going.