It's one of those questions people like to ponder. Which came first, the chicken or the egg?

While your response may offer insight into your mental makeup, degree of education, or even your religious beliefs, there's one thing it won't do: provide a definitive answer to settle the matter.But that's okay. Answering the question is just for fun. It's not a life-or-death matter. Answering another which-comes-first question, however, may be.Which comes first, obesity or laziness?In about two generations, obesity has gone from minor medical malady to a full-blown epidemic, with nearly 35 percent of American adults and 17 percent of children now considered excessively overweight.According to the National Institutes of Health, the ill effects from weighing too much create the second leading cause of preventable death in the United States, a close second, in fact, behind deaths resulting from tobacco use.An estimated 300,000 Americans a year die from the lack of fitness produced by an abundance of fatness.Yet the problem is not ours alone. The most recent projection in Canada has obesity becoming the leading cause of death in that country by next year, and many Western countries or countries whose citizens willingly adopt the Western diet are experiencing scary spikes in weight-related deaths.Ask people from these country, and they're likely to say that this new increase in obesity creates laziness, that lugging around 25, 35, or 45 unnecessary pounds makes everyday activities harder, thereby making the overweight less likely to do them and more likely to sit on that already large behind.But recently, researchers at UCLA performed experiments with rats that suggest that the laziness actually comes before the weight gain, that laziness is a byproduct of the fattening food that adds to flab.Using rats to learn about humans, by the way, is a common practice in research. A rat's physiology is similar to a human's, so both tend to react similarly to changes in diet and exercise.For three months, researchers fed 16 female rats a normal rat diet of unprocessed foods and another 16 a diet of primarily processed foods high in sugar. In that time, the expected occurred: the second 16 became obese. The first 16 did not.But something unexpected occurred, too. When the researchers made the rats work for their food and water by pressing a lever, the now-fat rats from the bad diet needed longer breaks between pressing the lever.In fact, in a 30-minute session, the now-fat rats took breaks that totaled twice as long as the breaks needed by those on the unprocessed-foods diet.In response, Aaron Blaisdell, the lead author of the research team from UCLA that published their findings in the April online edition of Physiology and Behavior, said: "Overweight people often get stigmatized as lazy and lacking discipline. We interpret our results as suggesting that the idea commonly portrayed in the media that people become fat because they are lazy is wrong.Our data suggest that diet-induced obesity is a cause, rather than an effect, of laziness."What happened in a later stage of the study further substantiates Blaisdell's belief. After six months, the rats in the study switched diets. For nine days, the fat rats ate the unprocessed-foods diet, yet their weight did not change.Neither did their rate of working the lever for water and food.Nine days of the bad diet, however, didn't increase the weight of the rats originally fed the unprocessed-foods diet for six months. Their work rate on the bad diet did not slow, either.Applied to humans, this suggests that quick fixes of bad diets do not work, but that occasional slip-ups by healthy eaters don't do as much damage as you might expect.For those of you left less than impressed by any study performed on animals and then related to humans, consider this: as a result of working on studies like this one, Blaisdell, a college professor recognized as an expert in animal cognition, made major changes to his diet five years ago.In an interview for Medical News Today, he said that as a result of avoiding junk food and eating "what our human ancestors ate," he's now full of energy and that he's "noticed a big improvement" in cognition, that his "thoughts are clear and focused."Could what occurred to Blaisdell be true for you? Is it possible that you currently feel less energetic simply because you're fueling your body with the wrong stuff? Stuff that tends to make you less likely to want to burn off the excess calories inherent in it?If you think that's a probability or even a possibility, experimentation is in order.If you're a notoriously bad breakfast eater, for example, commit to consuming an optimal breakfast maybe 8-to-12 ounces of Greek yogurt with a serving or two of fruit and a high-fiber cereal for at least a month. Keep a journal of how you feel before lunch for that month.If at the end of the experiment you find that eating a better breakfast helps you in the morning, it should motivate you to make similar changes to your other meals.