@Rain1234  
Genetics and calorie intake play a role: some people have faster metabolisms. Humanity evolved in ha environment of scarcity, as such our bodies evolved to try and cling on to as much energy(fat) as possible. It’s only in the last century or so that many countries have large excesses of food that people can gorge themselves on.

I belive dna controls when fat is stored not calorie intake, becose i am very thin and i eat unhealthy amounts of sugar and salt and the bad transfats.

is he fat or anorexic, he can’t be both lady

@Background Pony #3A1C  
@Tavi959
 
It’s actually not unhealthy at all; we just live in a modern society where it seems unfathomable to go multiple days without food. But there are zero studies that show there’s anything unhealthy about it, quite the opposite, you don’t lose muscle mass (that’s a myth), and the average person can go a month without food. Gandhi at 74-years-old went on a hunger strike for more than 20 days. People all over YouTube do it, and report what’s happened and it seems fairly consistent.
 
Our ancestors from the 19th century on back, and some places around the world go regular periods without food and then have time set where eating can be done. Being able to eat every day is a modern health luxury, not a biological necessity.
 
Weight loss by absolute zero caloric intake for at least a few days at a time will actually stay off permanently; it’s extremely difficult to yo-yo.
 

This doesn’t sound healthy.

If you can see bone, stop and eat food.

That diet (just like many, many, many other diets) is super unhealthy, and it’s liable to kill you if you stay on it, but if you quit, your weight will just go back to normal.  
If you want to lose weight, watching and limiting your caloric intake is a good step (though the limit probably should be a bit higher than 600), but if you want keep it off and not put your health at risk, then you need to exercise. It’s a hard habit to get into, but, like pretty much everything else, it’ll get easier as you get used to it.