- Count your calories. (Myfitnesspal App has a barcode scanner. Use it.)
- Find out your Base Metabolic Rate
This is the bare minimum calories you likely burn every day. There’s slight variation, but not much. You aren’t a special snowflake (unless you actually have a diagnosed condition, in which case my advice isn’t aimed at you).
- Two options here: A) You eat at 500 calories under the above value every day. This adds up to being negative 3500 calories a week, which is equal to one pound of fat and not very hard to deal with. B) You start exercising (or continue doing so) with lifting (and possibly cardio if you want to, though not necessary at all), and eat at your maintenance for two weeks. Track your weight and how you feel as far as recovery from your workouts are. If you’re dropping more than 1 lb per week, raise your caloric intake up. Simple equation (with “x” being some number above “1” and “y” being the amount you need to increase) is y=500x. Thus if you’re dropping 1.75 lbs per week and want to adjust to just 1 lb per week, y=500(0.75)=375 calories.
Depends on your goal.
If you’re trying to just gain weight and aren’t concerned about maximizing muscle growth or staying terribly lean, follow the same advice as above, making your diet a 500 calorie surplus every day.
If you want to put on muscle and stay lean, increase the calories by around 200 – 300 per day and watch your weight. You should only be going up a pound every 2 or so weeks. This will help to, slowly, gain muscle while gaining little to no fat.
Found the studies on @Iwannaburnfat on IG. Dude is fantastic for more in depth looks at the process.