I think one has to ask a lot of questions before you can find the salient questions...diet and exercise do work, it's basic thermodynamics at play. How can individuals keep themselves motivated to stay on a regimen of fewer calories and more activity in a western world of perpetual plenty and sedentary work?

We weren't this fat earlier...even as recently as the 1970's, obese people were rare. According to http://lanekenworthy.net/2012/05/31/why-the-surge-in-obesity/ the most likely culprit isn't TV or the internet or more sedentary work, it's increased caloric consumption. Think of the 64oz Big Gulp at 7-11. 744 calories for a (non-diet) coca-cola at that size! And portion sizes keep going up in restaurants and grocery stores, given that even if its just 30 cents or a dollar to upsize a fast food meal, the added food in the portion costs much less than this, boosting profits on the sale. It's certainly in the immediate interest of businesses to maximize the wealth of their shareholders by boosting the profits of each sale. Consumers want a bargain. Both producers and consumers will resist any attempt by a government to regulate the portion size of food as an unwelcome intrusion of their freedom. Yet it will be the government and the health care system that will bear the external cost of their own populations slowly digging their own graves one fork-full at a time.

An effective solution that can be implemented into the society we have right now seems impossible for me to imagine.

You already can. Order the 23andme Autosomal DNA test, spit in a cup, mix in the preserving solution, send the kit back, wait a few weeks, and log into the site to see your results. You have to click on an extra option to reveal your status, as they are mindful of the fact that most people don't want to know what their status is, given that Alzheimer's Disease is, at present, incurable, terminal, and no available treatment has been shown to slow down its advancement. My father had Alzheimer's Disease, and we both chose to get tested and I chose to look at the full results. For the Alipoprotein E4 marker, he was an E3/E4, and I am an E3/E4. This is the 2nd highest risk group...those with E4/E4 are virtually certain to get the disease. He was diagnosed at about 68, and he died at 74.

The tricky part is that none of those tests will tell you when you will get it. Any dementia that would strike you 10 years after you die of pancreatic cancer isn't relevant. Half of all people who are fortunate enough to live to be 85 will have some measurable amount of dementia. If I could make it that far with at least some basic level of mental and physical health, I think I would be grateful for cashing out the operational lifespan of a human male, and accept my eventual death as a simple fact of nature.

I am at peace with it. It isn't as if dying of heart disease or cancer is a walk in the park either. I might die of something else before then. My mileage will vary. Statistically, it's far more likely that I will endure a slow, lingering enfeeblement...with whatever level of dignity I'll be able to muster at that time.

I'll leave you with a quote from the famous biologist Richard Dawkins...

“We are going to die, and that makes us the lucky ones. Most people are never going to die because they are never going to be born. The potential people who could have been here in my place but who will in fact never see the light of day outnumber the sand grains of Arabia. Certainly those unborn ghosts include greater poets than Keats, scientists greater than Newton. We know this because the set of possible people allowed by our DNA so massively exceeds the set of actual people. In the teeth of these stupefying odds it is you and I, in our ordinariness, that are here.We privileged few, who won the lottery of birth against all odds, how dare we whine at our inevitable return to that prior state from which the vast majority have never stirred?”