What Causes Obsessive Behaviour About Food Intake?

OK, I've not done this sort of thing before, so bear with me. I'm trying to find out about a psychiatric problem, If I can call it that, which involves one person controlling what another person eats. I've met 3 men who do this, seemingly unable to control their activities. After he had been away on a business trip, my first husband would go through the garbage surveying the remains of what I had eaten whilst he was away. He told the marriage counselor, "That's part of my job, as her husband, to keep track of what she eats." His brother, would follow his wife closely at a buffet & tell her what she could, and couldn't eat, and how much of each item she could have. I recently contacted my high school/college sweetheart & he had developed the same issue. He made it clear that he would be monitoring how much was on my plate when I visited for the holidays. Back when I was married, I wasn't fat. I suppose I'm 50 pounds overweight now, but my "sweetheart" was very much impressed with "how good I looked for my age". I suspect that this mania is far more widespread than I have encountered. Yes, it is in the control sickness area, but I really think there is something separate going on here relative to food. How can I research this to find out more about it. I always seem to find the Internet lacking in the information that interests me.