Starting a exercise routing or increasing activity makes you hungrier. However, if you time your meals correctly you can prevent this and make it easier to stick to your healthy goals. Make sure that you have your intake matched around when you have your expenditure (exercise).
If you are a morning exerciser, do not make the mistake of having nothing before your workout. If you have a sensitive stomach then keep it to liquids (juice, sports drink, coconut water) or carbohydrates such as a piece of fruit. Especially if you have less than 1 hour before exercise. Then make sure to consume a snack or breakfast with protein and carbohydrate within 10-30 minutes after exercise and a meal or snack within 2 hours. Your larger meals should be breakfast and lunch. Match your fuel intake with your expenditure.
Lunch time workout. Have a balanced breakfast within 1 hour of waking and take your lunch split it in two. Have 1/2 before the workout and 1/2 immediately after then consume your morning or afternoon snack, whichever you notice your internal hunger cues are asking for.
Evening or after work workout. Have a balanced breakfast, mid morning snack, lunch and have a snack before. If you are 1 hour before just carbohydrate, if 2 hours before carbohydrate and protein. If you are not able to have dinner within 10-30 minutes after have a snack with carbohydrate and protein until you can have dinner.