You can get some fat on your forehead when you gain weight.
Although the amount of fat that you get in your forehead from gaining weight is very little and hardly noticeable at all.
When you gain weight you'll notice most of the fat in your stomach, belly, legs, arms, and sometimes hands and feet.
Most of the fat does not go to your forehead but more of the fat can go to your face as well.
So as you gain weight you might also notice you have a fatter face as well.
Face fat is stored in parts of your face and you can also lose that face fat.
But it takes longer to lose face fat and forehead fat than it does to lose weight in other parts of your body such as losing belly fat, stomach fat, leg fat, buttocks fat etc.
Weight loss surgery can help you lose weight much faster but there are some risks and weight loss surgery is expensive as well.