Don't feed the rats! (at least not too much)

I am currently reading “The behavior of the laboratory rat” and I found a very interesting point : don’t feed your lab rats too much or they will suffer and your experiments can suffer from that too! Of course, letting them have food ad libitum is the easiest way of doing. And we may think that they will only eat what they need. But rats are greedy! Unrestricted access to food is “unnatural” and compromises the health of the rats : it may cause obesity, diabetes, tumors, it shortens the life span and reduces the cognitive performance (formation of free radicals and/or glycation reactions of sugar with proteins). On the other hand scientists showed that dietary restriction is associated with increased production of proteins enhancing neuroplasticity and increased protection against metabolic insults like BDNF.

I was really astonished by this chapter written by R.L. Gibb. But if I agree to restrict food available to my rats, how much should I give, exactly? Maybe this article from Markowska and Savonenko will help (I should find it and read it).