A subtle way of breaking down a person and weakening their ability to argue is through dietary control. This causes the Brain Syndrome, where an imbalance of nutrients leads to confusion and an inability to think clearly.
This is usually implemented by a range of constraints.
Sometimes there is just not the money available to spend on food. As a result, limited amounts of food are offered, and the variety of nutrients may not be sufficient for normal body and brain functioning.
One argument that may be used is that money is somehow bad, a sign of material selfishness. As a results little is spent on anything, including food. Any money the people have in savings are extracted and may go to pay for ‘spiritual’ things.
Sometimes also there is relatively little money available. If the group spends a lot of time in prayer, discussion or general ‘good works’, then the money is not earned and there is less available to buy food.
Groups often isolate themselves, often far from civilization and sources of wider ranges of food. They may grow their own food, much as monks in monasteries have done for centuries, although the chance of a balanced diet can be less likely.
A characteristic of isolative groups is that they fully occupy the time of their followers. They may be out working, in study groups or in solitary prayer or contemplation.
When there is less time to eat, then meals are more constrained and may be considered as interruptions of more important items.
Religious groups may put different emphasis on eating, including moral constraints, as above.
Periods of non-eating are common amongst a number of traditional religions and is hence a known pattern. More control-oriented groups may use this paradigm to reduce eating and hence weaken people they are converting.
Another variant is that there are ‘special foods’ that must be eaten. These may contain more of one nutrient which, whilst good for you in moderation, can be damaging in excess.
Just increasing one food, such as rice, can result in less of other foods being eaten, again resulting in imbalance.
In the way that there can be special foods, there also may be foodstuffs that are demonized and avoided. When these cover whole classes that contain particular nutrients, then an imbalanced diet may result. Even vegetarianism can result in imbalance if meat nutrients are not replaced.