Jeffrey: all the science (and I am addressing you layman to layman) says that once we have lost a bunch of weight, for the rest of our days the body wants it back. Will find ways to get it back. So part of the battle is to recognize where a) you might be allowing yourself more foods than the 1200 calories, which isn't sustainable (nor are any diets) and b) sneak snacking and food consumption we aren't counting in the overall calories, and finally c) it's not just about calories. Most true lifestyle changes are for life. Period. They are not temporary. That is how I did and have done it for almost 35 years. I changed my eating habits and did not reintroduce them. That weight will come back if I revert to previous habits. And fast. I am not a fan of strictly caloric restrictions, for the inevitable happens, often so quietly and surreptitiously that we don't notice it. An ounce here and there, then a pound, then ten.
The only answer I have is to hire a top nutritionist who can work with you for lifestyle changes. The pandemic was the outlier for all of us, however, for stress is a huge piece of this, and I am not at all surprised. For my health dollar, I have continued to focus on functional fitness, not weight, activity, not exercise with the intent to lose or control weight. Those I have discarded. I find good food, that is for my body, my age and my activity level, easy to love for I feel good when I eat that way.
This is a lifetime journey. We always feel good if we drop a chunk. The maintenance is so hard. Research says that the third and fourth years are when it creeps back on. Once lost, it's like creating a DMZ between your current waistline and the foods that want to waste that waistline, Jeffrey. There is no easy answer, and as we age the body changes constantly. I know that's not an easy answer but it's all I've got.