i personally know many people who struggle immensely, despite eating far less than me.
for me, it takes exactly 0 effort to remain thin. zero. i literally don't even think about it. other people count every single calorie they eat, exercise religiously, take weight loss medication, and still have trouble managing their weight.
but hunger is a primal thing - some people are far hungrier far more often than other people, for many reasons - and yes, it takes energy to resist hunger.
money and free time aren't required, no, but it definitely helps your odds.