Yes, I think it is better to limit their food intake.
When a person get freedom to eat anything, he will be allowed to eat whatever he want. - When a person gets the freedom to eat anything, he will be allowed to eat whatever he wants.
I'm not saying it's completely bad,
But if he want only fast foods like hamburgers, he will be fat. - But if he wants only fast foods like hamburgers, he will get fat
It means that his health can be dangerous. - It means that his health can be in danger.