You don't need to diet - ever!
You just need to eat better by remembering these simple rules:
Every day is not a special occasion. We have a culture of celebrating with food but when that creeps into everyday life, we put on weight. Leave the cake for birthdays, ice-cream for a day at the beach, chocolate for valentines etc. Make high fat/high sugar items 'special occasion' food again and when you do have a celebration, don't go overboard.
Never drink fizzy drinks or squash (cordial) - even for special occasions. It just isn't worth it. No nutritional value whatsoever and we have all read to articles about artificial sweeteners. Why risk it?
Have protein with ever meal. Protein makes you feel fuller for longer so you don't need to snack.
Drink plenty of water. Our bodies can tell us that we are hungry when we are really dehydrated.
Get plenty of sleep. Studies show that a lack of sleep can alter your hormones and lead to an appetite change of wanting high calorie foods. It can also make you not want to exercise.
Don't demonize a food item. We all know what makes us loose control. Mine is chocolate. If I demonize chocolate and tell myself that I can never have it again or I am being 'naughty' by consuming it, then I will think of nothing else. Allow yourself your 'guilty pleasure' and enjoy it when you do. Just remember rule number 1.
Exercise regularly - remember the energy (calories) you put into your body needs to also be used or it will be stored as fat.