Will I see an improvement in strength if I exercise daily but I don't watch my diet?

I exercise daily but I'm not motivated enough to diet. I eat quite healthy (almost no processed foods, a lot of fruits and vegetables etc) but my biggest problem is portion control and I have noticed that I am slowly but surely gaining weight. Will I see an improvement in my strength and endurance if I keep working out, or there's no use in doing it if I don't have a proper diet?
Will I see an improvement in strength if I exercise daily but I don't watch my diet?
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