I’m not an expert but like you said, excess calories are turned into fat (assuming you aren’t lifting weights and turning it into muscle).

Excess weight carries all sorts of issues such as diabetes, heart disease, cancer etc…

It will also be harder on many of your joints such as knees and ankles.

It can also cause self esteem issues if you are bothered by the way you look.

Eating a healthy, balanced diet, coupled with exercise has many, many benefits, both physical and mental.