I think this probably has to do with the sugar in our diets. Animals that live in human environments tend to eat refuse from our food, and our food has been get

I think this probably has to do with the sugar in our diets. Animals that live in human environments tend to eat refuse from our food, and our food has been getting more and more packed with sugar lately. The explanation about animals having access to more food does not work. In the wild, if there is more food, you will simply get more rats. Wild animal populations tend to rise to match their food supply without giving much opportunity for animals to get fat. Unfortunately, the sugar explanation does not quite explain the lab rat observations. It is possible that the lab rat food has been augmented by sugar without the scientists noticing. AFAIK lab rats tend to be fed commercial food mix that is purchased from various suppliers. The other explanation fits the lab rat results much better but it is much scarier. It is possible that due to GM crops and/or cattle food supplements we may have released some new hormone in the food supply and/or the water that makes us and animals fat.