Weight maintenance is a basic balance of enery in vs. energy out.
The units of energy used by our body are calories. Eating food brings calories into your body for energy, and exercising burns calories to give you the energy to move.
Folks gain weight by having a positive enery balance (ie: they are taking in more calories than they are burning off- so the body stores the energy as fat)
Conversely, you lose weight by having a negative energy balance (ie: you are taking in fewer calories than you are burning off- therefore your body utilizes the energy stored in any excess fat burning it off)
And folks that maintain their weight have a nuetral weight balance (ie: you maintain a consistent diet, that is complemented by your exercise regiment)
If you decrease 500 calories from your energy balance each day (by consuming fewer calories, and/or burning more calories through exercise) you should lose 1–2 pounds per week. Which is a healthy pace for weight loss.
Don’t fall for any fad or magic bullet program that has you dropping 20 pounds in 10 days. You will shock your metabolism, and you can bet that all that weight will come back (plus a few pounds).
Once you reach your healthy (not emaciated) goal weight, you’ll need to balance out what your sustainable diet and exercise regimen will be. I recommend you talk with a registered dietitian if you need help setting goals.
Good luck!