If your eating low calories already, you’re going to need to increase your daily activity. Things like working out. Even things like a 20min walk, taking the stairs, parking further away from the shops. Are a good place to start if you can’t workout straight away
Protein at .85 grams x bodyweight. Example someone weighs 190, their protein intake is 190×0.85= 161
If this sounds like a lot, purchase whey isolate or pea protein. Do two scoops at a time for 40 to 50 grams extra. Do more if struggling to eat enough, 4 oz of chicken or beef is about 25-35grams.
Increase servings of fish to at least 3 per week for healthy omega3 fats and to improve hormone function.
Eat according to workout schedule, leave starchy carbs to after workouts.
Lastly do not over restrict, especially if working out.
First steps – Increase protein using guidelines mentioned, drink 8-10 glasses of water, have starchy carbs after exercise (whether an actual workout or physical job)
Increasing your protein will increase your calories slightly but not drastically (lean meats or protein powders) and if you are restricting thus may help kick start things again.
If you see some results and those simple steps do not overwhelm you, look into reverse dieting (slowly increasing calories to wake up metabolism). – combine reverse dieting with exercise