you lose weight by calories in calories out. it doesn't really matter if you replace food, but it helps in the long run (lose water weight faster ex. replacing your carbs (bread) with complex carbs (veggies) ).
Eat white meats (chicken breast is the best with little seasoning and grilling or oven baked)
Eat veggies
Try to avoid rice (brown rice is ok)
Drink a shit ton of water, like i mean a shit ton, every single time you read a comment on this board drink a glass
Protein shakes can be used as meal replacement
You can hit the gym if you want, it's up to you.
Want to lose weight faster, but look like a fucking weirdo? Go do cardio only
Want to lose weight, and have some muscle? Follow a beginner program (usually 3 days a week) and do cardio on the side
Want to lose weight, and be toned? Do a PPL program (push pull legs) (6 days a week) and do cardio everyday.
Heads up, when you lose weight you don't gain muscle. You will make some noob gains which will increase your strength, but gaining muscle = gaining weight.
My advice to you:
If you have a gym membership do a 3 day program (i recommend strong lifts)
Do cardio after your workout for 1 hour (it could be the stationary bicycle, step master, or jog + run) andything that keeps your body moving
Stack up on protein (chicken breast, shakes, egg whites)
To calculate your calories, multiply your weight by 15, subtract 1000, eat that many calories. If you want to go more in depth use a calorie calculator.
This post is kind of a mess, but fuck it, i haven't slept in 39 hours.
>t.former gymcel that gave up and is now a fatcel