I have a patient who weights 550 pounds, according to his intake form. I didn't weigh him. I was afraid he would fall or damage the scale, and I don't say that to insult him.
Who knows how he got that way. No time to fat-shame.
He has a long road ahead if he ever wants to be healthy again.
Where does he start?
1 pound (or kilo!) at a time.
Don't worry about sugar, macros, or any of the other small details that tend to get a lot of attention in the fitness world.
If he focuses on the end goal, he's never start. It's too daunting. He should focus on 549 and nothing else. Get some wins and get them early.
It doesn't matter if he weights 550 or 150. The principles apply at every weight.