They didn't go to the doctor regularly, so if any were diabetic, they would not know it, and would not be able to obtain insulin without a prescription. It is highly doubtful that they withheld food for any "good" reason.
You keep mentioning context. The context here is that they were all malnourished to the point that they had to be hospitalized, chained for weeks and months at a time, never saw a dentist, rarely saw a doctor, etc. In context, it is highly unlikely that there is a benign excuse.
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There also is the fact that medical professionals treating the children have told the news media they have left their rooms in tears. These children weren't just denied food for short periods of time such as no cookie before dinner; they were denied food for extended periods of time to the point it stunted their growth.