Just like my ex. When we figured it up, he was receiving at least 1200-1400 calories a day via alcohol and pop He was only around 5'6, and that was pushing it on a good day, and I'd say med boned for a man. When we were together, I cooked fairly large, sit down, family style, meals every night. He still drank a lot of calories during that time too, and even though he was more active, and working then, he got a bit overweight during that time...
When we split he just drank. Period. He couldn't boil water and wouldn't even heat anything up for himself in the microwave. However, although he was sedentary (very, very, very sedentary), and was getting at least 1,200-1400 calories, via alcohol and pop, yet he was still severely malnourished. He was getting calories, but zero, to little, nourishment.
Also, his friends, and our son, saw him regularly, so they didn't see the change. It was slow, so their eyes adapted to the physical change. I didn't really notice because he was always sitting down when I saw him or he had on a
baggy shirt, and
sweats. I knew that he looked like Hell but he was an alcoholic who'd, sadly, lost any interest in his appearance quite some time ago.
The link below is about nutrition, hunger, and malnutrition. Even if the kids had gotten a Taco Bell soft taco (170 calories) and a large pop (380 calories), one time per day, for years, there would not have been enough calories or nutrients to keep them from becoming malnourished.
http://kidshealth.org/en/teens/hunger.html