Salamu Alaykum all and Ramadan Kareem!
From my own experience of Ramadan, I can say that fasting not only makes me stronger, but it also has benefited my health in countless ways. During Ramadan, I am in my best shape, I have the most energy, and my (not to be crude) bodily functions are all working at top notch.
I also notice that fasting helps you to regulate your metabolism. Throughout the year, my body now requires less food as it uses it more efficiently and is storing far less as useless fat. I also am able to fast easier every year, as my body is now accustomed to ketosis, or changing its energy source from food in the stomach/intestines, to fat stores. For me, Ramadan is a blessing, and everyone should try to do it if they are able in my opinion.
If they are able of course is a big issue, which is why God so brilliantly and explicitly laid out the criteria in the few verses that exist on Ramadan fasting, I think we all know them well. So that guy with diabetes, obviously was going against God's recommendation in the Qur'an, for example.
Additionally, as other forum members mentioned, fasting in general is actually prescribed as a cure for many diseases. Here are a couple links on that information:
http://www.allaboutfasting.com/benefit-of-fasting-degenerative-diseases.htmlBeneficial effect on serum apo AI, apo B and Lp AI levels of Ramadan fasting
http://www.sciencedirect.com/science/article/pii/S0009898197002453Of course, everyone's body chemistry is slightly different. Thus, as God says, if it is an extreme hardship on you, then feed one poor person for each day of the fast (this is a good thing to do anyway).
Salaam everyone and Ramadan Kareem!