Insulin regulates blood sugar
When you jack your blood sugar up high chronically through a sugary diet it causes insulin to be released in huge amounts in order to regulate all the blood sugar
Then when there's so much insulin around, you cells become resistant to it
This causes you to secrete even more insulin to get the blood sugar down
At the same time that you are resisting insulin, all that insulin is converting all the blood sugar to fat ASAP
This causes you to gain weight at an accelerated pace (as long as you continue eating sugar)
Eventually your pancreas (the thing that produces insulin) can't take it and shuts down which is type 2 diabetes
Okay say you are fat and want to avoid this and you decide to lose weight using conventional means (caloric restriction)
If you have the same meal frequency as the standard American diet, you are still increasing your insulin every few hours (because it gets released every time you eat).
So even though you reduced calories, you didn't fix the underlying hormonal issue. The lack of calories will increase your hunger hormones the longer you're on the restriction. A couple years out, it becomes a kind of psychological torture to not eat. Then people give in and rebound to their body set point which is based on their hormones.
By fasting you can lower your baseline insulin levels so the pancreas learns over time to secrete less. Fiber also has an effect, I think vinegar does as well. But one of the largest effects is building more muscle mass. More muscle requires more calories to operate so it increases metabolism, letting you eat more and be more satiated. It also reduces your resistance to insulin significantly, clearing out this hormonal problem over time.
So lift weights and eat one meal a day or every other day if you are obese.