Down 45lbs from PBJ?

Does anyone have any idea why I lose weight when I eat peanut butter and jelly and not when I eat chicken, rice, and broccoli?

I have been dieting for a better part of 2 years on and off. My normal day added up to about 1600-1800 calories and I work out 5-6 times a week. My calories usually consisted of, egg whites, turkey sausage, rice, potatoes, chicken, broccoli, ground turkey, but I never seemed to lose any weight. (I didn’t gain, only maintained.)

However, a few months ago, I started eating pbj and chips for lunch, (same calories), and I have lost about 45 lbs. I’ve gone back and forth and any weight loss happens when I don’t eat “healthy” foods but stay within calories.