I think it's a great thing what Krispy Kreme Doughnuts is doing. The health care of the US has nothing to do with them giving back to there valued customers. Proper health care starts at home and Krispy Kreme Doughuts should not be held accountable for carelessness within the household
Despite poor health and obesity problems in the US, Krispy Kreme has the right to give away free donuts if they want to. They do not have a moral obligation to not provide extra donuts, and no one can force them not to. It is a business decision and they want to attract more customers.
Krispy Kreme is in the business of selling donuts, and they make no pretenses that donuts are health food. The same reasoning would apply to any food business that sells food that is deemed to be unhealthy. As a private business, Krispy Kreme has a right to run a promotion and shouldn't be penalized.
Obesity is indeed a serious health problem in the US and doughnuts can certainly contribute to it. However, although it would be helpful for Krispy Kreme Doughnuts to find some way of promoting healthier lifestyles, it is not their responsibility. If Krispy Kreme offers two dozen doughnuts for the price of one, there is no requirement that they be eaten in one sitting or by one person. To make them into a scapegoat for poor healthcare education or lifestyle choices seems unreasonable.