Following up on yesterday's discussion, Losing Weight After 45 (ooh, these strenuous links!) posted a link to this study. Which was fascinating to me, because the rats were subject to "Cheat Day" type conditions (lab chow all day plus junk food 1 hour a day) in addition to a control (lab chow only)and a free access situation (lab chow or junk food 23 hours a day.)
Interestingly, the 23 hour access rats got fat. They also developed some distressing brain changes similar to those you see in human drug addiction, even ignoring an aversive cue (they had been trained to fear a certain light cue preceding a shock). They were so focussed on the junk food they kept eating it even though the light was flashed. If you've ever read the moving blog Escape From Obesity or similar ones describing the problem of compulsive eating, this change in brain chemistry really fits with the subjective experience the writers describe.
The 1 hour access rats got a little fatter, but not significantly more so than the chow-only rats. The authors concluded that the 1-hour access rats didn't develop the same addiction-like reward deficits (whew!) or eat significantly more calories than the chow-only rats. But they did (let's face it) binge during that 1 hour. They just ate less the rest of the day and more when the ho-hos and bacon came out.
So it looks like the best situation for both humans and rats is to be fed nothing but a nutritious chow until you're sacrificed at the end of the experiment and get your spleen weighed. No, no! Just kidding!
Failing that, I'm guessing that what works for most people is regular meals consisting of highly nutritious food. Some people do great with regular access to junk food (however you choose to define it). They can eat a little and their reward centers light up and they go happily about their business. Others seem to need to limit access (raises hand). I keep chocolate around and eat a few squares daily. But I can't keep, say, pastry or malted milk balls in stock-- just askin' for trouble. My husband wouldn't be able to resist Doritos (which are dusted with cheese flavored crack, I'm pretty sure.) A few people seem to need to stick with the lab chow only.
Of course people are not rats, except possibly Sandra Bullock's husband. (Wonder how much his spleen weighs?) But it's all interesting stuff unless of course it happens to directly contradict your own pet health practices. Then it's just another worthless rat study :)