Metabolic set points can and will drift over time. So if somebody starts out with a setpoint at 22 BMI, they might naturally be anywhere from 21-24 BMI at any g

Metabolic set points can and will drift over time. So if somebody starts out with a setpoint at 22 BMI, they might naturally be anywhere from 21-24 BMI at any given time. As food in the environment becomes more hyper-palatable and calorically dense, people are more likely to "settle" at the upper end of this range. Over time spending more time at the upper end of one's range will "nudge" up the setpoint gradually and continuously. But the point is this is a slow and continuous process that occurs over years or even decades. Discontinuously making a big shift in weight, up or down, is basically impossible. Which is why despite very high rates of obesity, it's basically unheard of for someone to gain 50 lbs in a short period of time. Almost all weight gain takes the form of 5 lbs one year, 5 lbs another year, and so on.