Your doctor told you to sort your diet out and now you are staring at a blank page

Your doctor said improve your diet and left you with a blank page and a vague sense of dread. This works out your estimated TDEE from your age, height and weight, sets a modest deficit for gradual fat loss without crash dieting, and splits it into protein, carb and fat targets with a one-line reason for each. Plain language, no jargon. For anyone told to start and unsure where.

My doctor has told me to improve my diet. I am {AGE} years old, {HEIGHT}, {WEIGHT}, and I want to lose fat gradually without crash dieting. Calculate my estimated TDEE, suggest a modest calorie deficit, then split that into protein, carb and fat targets with a one-line reason for each split. Keep the language plain: no jargon.