Pretty much anything that is edible. Christians do try to avoid large amounts of alcohol; but that's about it.
The prison I was in allowed diets. Like kosher diets, diets based on any allergies, etc.
There are different types of routine hospital diets depending on why a person is hospitalized. There are low sodium diets, regular diets, soft diets and liquid diets.
Fad diets
No there is not a legal age for diets.
http://www.diet-i.com/ has information on TONS of diets. It tells you what the best diets currently are, gives you reviews of diets and even has a section for special diets.
CAUSE DIETS ARE BAD
It is just like food diets, but with liquid.
Mostly fad diets such as the Sacred Heart diet and the cabbage soup diets have been debunked. These are extreme diets that are in no way healthy or maintainable. The detox diets have also been know to not last.
If one follows a diet plan it can work. The issue with diets is that not all body compositions comply with diets. It's a trial and error process with diets.
Easy to follow diets can be found on reporting sites, such as USNews. They have articles filled with easy to follow diets. One of them is even called "Easiest Diets to Follow".
no citric acid is not good for your diets.
dogs have diets because some dogs are to fat or they are obese, but some dogs go on diets because the are sick or have a disease or some dogs go on fattening diets to grow fatter because they are to thin.