Diets and fasting affect people in different ways according to their types, it is not 100% the same in all people, not even close. I am the type that had to lift weights and eat like a horse to put mass on myself. I had a friend that ran like 5 miles per day on Monday-Thursday, then ran 24 miles on Saturday. He ate lunch with me practically every day (we worked together) and ate like lettuce and water, really strict. I ran nothing. Yet he was chubby and I was buff.
I came back to the Church, got married and never lifted weights again. I still ate without any controls. I started fasting during Lent, I found that any weight that I lost was replaced by fat around the midsection when I began eating again. The fasting seemed to have changed my metabolism, and now I had to be more careful what I ate. I'm never going to be fat, it is not in my nature, but the fat does now get around the waist, even though I eat less, whereas before I ever fasted not a trace of fat stuck to me.
I am now on the Keto diet and I see that it is eliminating the fat around the waste and not all over. I went from a size 34 to a 31. It also has made my life long heartburn disappear, and also my life long propensity to cramp up. My joints are very limber now too.
My fasting during Lent was not a total fast or anywhere close, it is what the Church suggested in the 1940's, as taught to me by my priest ordained in 1952. Only one meal with meat per day, and the two other meals can't equal the one meal. One can easily cheat on the instruction by pigging out on the one meal and then they can eat two smaller meals that are one ounce less. What I di is have two eggs in the morning. Then hold out till like 5pm and eat dinner. Then at like 10pm I'll have a piece of cheese and an apple. Or a piece of sprouted bread with a piece of cheese.