About "thin gluttons": Yes it is possible to be very thin and eat a lot. But is this a "glutton" in the sense that the Watchtower Society made it look to be? Probably not. Some very thin people have extremely high metabolisms, and they can eat all they want without putting on any weight. Were they to moderate their eating, their metabolism would slow down. More likely than not, they would lose muscle and healthy tissue and eventually get fat. And they would be unhealthy.
Also, very thin people that eat heavily may do so because of getting lots of exercise. Many Witless jobs are very demanding physically. Others might live in regions where the field circus involves hours of walking every day. Remember, if you walk an hour a day at a steady brisk pace, it is very difficult to become and remain fat. If you walk 8 hours a day like this, you are going to have to eat a lot to maintain a reasonable weight, and getting fat would be almost impossible. Back when people had to do that all the time, people regularly consumed more than 6,000 calories a day and never got fat. They burned them all off.
Gluttony is not determined by the amount that someone eats. It is determined by their attitude toward food. Usually it is a treatable eating disorder, similar to anorexia and bulemia. And one of the treatments is to allow for some degree of imperfection (most eating disorders result from perfectionism, something that the Puketower Society demands). A pure glutton is one that eats all the time, and is all-consumed with eating. There is not anything physically wrong with this person (some diseases increase appetite and metabolism). The eating interferes with their work performance. They would be eating non-stop while working (I did work with one true glutton: he was very fat, and always had something to eat at all times).
I think the Watchtower Society had better get its priorities straight. Gluttony is often caused by stress. Reducing the stress is the treatment (therapy is also recommended). They add more stress if they hound and threaten to disfellowship gluttons. It is true that these people are "greedy". But many are sick. They are under too much stress already, their lives are full of boredom and stagnation, or both. The field misery and meetings add to both stress and stagnation, worsening the existing gluttony and creating new gluttony problems (anorexia and bulemia also). Besides, this encourages people that are not true gluttons but that have a very high metabolism, a disease that increases appetite, or exercise a lot to be hounded for it. It also encourages fat people that are fat because of slow metabolism or not exercising enough (too much driving in the field circus, perhaps) to be hounded.
There is a cure for most true gluttony. Stimulate the person with highly enjoyable work. This will allow the person to not think of eating (remember children that are engrossed in play when dinner time comes will usually be reluctant to interrupt their play to eat.) Tedious work like the field circus is NOT emjoyable: if a person truly enjoys their work, a coffee break or lunchtime (or quitting time) will be seen as an intrusion, not as a welcome break. Get them involved in something that they truly enjoy. Allow them to play, preferably learning all the while. I bet their preoccupation with food will die off and they will become more normal. If that means no more Watchtower Society, so be it.