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Why Yo-Yo Dieting Leads to Long-Term Weight Gain

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You’ve probably heard that yo-yo dieting can backfire. Now we have some idea why: Scientists say that intense food restriction teaches the body to hold on to any calories and fat it can get. The researchers published their findings in the journal Evolution, Medicine, and Public Health.

There are oodles of diets out there, each promising that it alone holds the secret to dropping pounds and keeping them off forever. But almost all these diets are short-term strategies. The weight we lose almost always comes creeping back in as soon as we go back to eating normally.

It’s something of an evolutionary puzzle. If carrying excess weight is physiologically inefficient—that is, it can be taxing for the body—why would our bodies work to regain what we’ve lost?

To find out, two British researchers looked in an unexpected direction: math. Animal behavior scientist Andrew Higginson of the University of Exeter teamed up with University of Exeter mathematician John McNamara to create a mathematical simulation of yo-yo dieting and its effects. Using what they knew about the behavior and physiology of existing animals, including humans, Higginson and McNamara created a hypothetical animal. They set it in a hypothetical natural world that followed the same patterns as our own. The animal had to eat to live, and being active used up energy. The animal’s food supply also fluctuated, as it does for real animals in real habitats. The researchers’ question was this: Would those fluctuations produce long-term changes in the animal’s body?

They certainly did. The simulation results showed that a body in inconsistent conditions like those in which our ancestors evolved would benefit from retaining any fat it could find in times of abundance. The results also suggested that the artificial scarcity created by dieting is a real trigger for this self-protective weight gain. According to the team’s results, on-again, off-again dieters are more likely to put on weight than people who never diet at all. And while this fact may be frustrating, the authors say, it’s actually a sign of a healthy body.

"The best thing for weight loss is to take it steady,” Higginson said in a statement. “Our work suggests that eating only slightly less than you should, all the time, and doing physical exercise is much more likely to help you reach a healthy weight than going on low-calorie diets."

But please remember: You're wonderful just the way you are.

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Animals
Owning a Dog May Add Years to Your Life, Study Shows
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We've said that having a furry friend can reduce depression, promote better sleep, and encourage more exercise. Now, research has indicated that caring for a canine might actually extend your lifespan.

Previous studies have shown that dog owners have an innate sense of comfort and increased well-being. A new paper published in Scientific Reports and conducted by Uppsala University in Sweden looked at the health records of 3.4 million of the country's residents. These records typically include personal data like marital status and whether the individual owns a pet. Researchers got additional insight from a national dog registry providing ownership information. According to the study, those with a dog for a housemate were less likely to die from cardiovascular disease or any other cause during the study's 12-year duration.

The study included adults 40 to 80 years old, with a mean age of 57. Researchers found that dogs were a positive predictor in health, particularly among singles. Those who had one were 33 percent less likely to die early than those who did not. Authors didn't conclude the exact reason behind the correlation: It could be active people are more likely to own dogs, that dogs promoted more activity, or that psychological factors like lowered incidences of depression might bolster overall well-being. Either way, having a pooch in your life could mean living a longer one.

[h/t Bloomberg]

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Live Smarter
Not Sure About Your Tap Water? Here's How to Test for Contaminants
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In the wake of Flint, Michigan's water crisis, you may have begun to wonder: Is my tap water safe? How would I know? To put your mind at ease—or just to satisfy your scientific curiosity—you can find out exactly what's in your municipal water pretty easily, as Popular Science reports. Depending on where you live, it might even be free.

A new water quality test called Tap Score, launched on Kickstarter in June 2017, helps you test for the most common household water contaminants for $120 per kit. You just need to take a few samples, mail them to the lab, and you'll get the results back in 10 days, telling you about lead levels, copper and cadmium content, arsenic, and other common hazardous materials that can make their way into water via pipes or wells. If you're mostly worried about lead, you can get a $40 test that only tells you about the lead and copper content of your water.

In New York State, a free lead-testing program will send you a test kit on request that allows you to send off samples of your water to a state-certified lab for processing, no purchase required. A few weeks later, you'll get a letter with the results, telling you what kind of lead levels were found in your water. This option is great if you live in New York, but if your state doesn't offer free testing (or only offers it to specific locations, like schools), there are other budget-friendly ways to test, too.

While mailing samples of your water off to a certified lab is the most accurate way to test your water, you can do it entirely at home with inexpensive strip tests that will only set you back $10 to $15. These tests aren't as sensitive as lab versions, and they don't test for as many contaminants, but they can tell you roughly whether you should be concerned about high levels of toxic metals like lead. The strip tests will only give you positive or negative readings, though, whereas the EPA and other official agencies test for the concentration of contaminants (the parts-per-billion) to determine the safety of a water source. If you're truly concerned with what's in your water, you should probably stick to sending your samples off to a professional, since you'll get a more detailed report of the results from a lab than from a colored strip.

In the future, there will likely be an even quicker way to test for lead and other metals—one that hooks up to your smartphone. Gitanjali Rao, an 11-year-old from Colorado, won the 2017 Young Scientist Challenge by inventing Tethys, a faster lead-testing device than what's currently on the market. With Tethys, instead of waiting for a lab, you can get results instantly. It's not commercially available yet, though, so for now, we'll have to stick with mail-away options.

[h/t Popular Science]

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