You exercised for 6 days and gained weight 1kg, which is a causal relationship. After all, fitness is a happy thing. If you think you can persist, you will have a sense of accomplishment. Personally, I think that a happy mood and relaxation are the main reasons for getting fat.
It's only a matter of time before you gain weight if you can keep exercising and supplement some nutrition.
I 172, about 1 18kg two years ago, and now it is close to 140kg. Hehe (not puffiness), keeping happy is the most important thing!