If feeding treats is a necessary part of life then use carrots, grapes or other fruits and veggies. Check the content analysis of the food you feed. Low protein, low fat foods are best. Some of them may only make the animal hungrier leading to the temptation to feed more. As with people there is some variation.
Exercise is part of weight management too, but it is overrated.
Very few of us have the time or the energy to exercise our furry friends enough to make a real difference to their weight. Exercise is more important for cardiovascular fitness and as an attitude adjustment than for weight control. Reduced calorie intake is still the only thing that works. One way is to ask your veterinarian. You can check easily yourself.