Entries for May 2008

When I wrote about exercising in the heat yesterday, I touched briefly on the issue of hydration. The June Nutrition Action Health Letter, published by the Center for Science in the Public Interest, offers much more information on how much—and what kind of—water to drink. One article is a Q&A with an expert on kidney function, discussing what science says about how much water people really need to drink. The other analyzes the ingredients in so-called water beverages like VitaminWater, Propel, and SoBe Life Water and concludes you are probably wasting money and calories if you're expecting these drinks to provide any health benefits.

The CSPI hasn't yet put up the latest issue online; check back in a week or so to see if it provides direct links to the two water articles. (The newsletter itself costs $10 a year.) In the meantime, here's a quick rundown on the water stories.

Six years ago this month, I did my first really long triathlon as a 30th birthday celebration. It was a lovely idea, but in practice it didn't really translate to a fabulous present to myself, since I trained in the New York City spring (cool, dry) and raced in Panama City Beach, Fla., (hotter than hell, humid) in mid-May. The 1.2-mile ocean swim was great, the scorching 56-mile bike ride considerably less fun, and by the time I got to the 13.1-mile "run" on black asphalt, I was wishing I were 29 again. I walked most of it, finished an hour slower than my goal time, and capped the whole party off with a half-hour on a chaise longue in the medical tent, covered by an ice-cube-studded towel.

Thinking back on that disastrous race compels me to share what I've learned since: that the key to continuing an outdoor exercise routine in the warmer months is to listen to your body, whose physiological mechanisms have evolved over hundreds of thousands of years to protect you from dangerously overheating. You have to take action, too, says Jonathan Dugas, an exercise physiologist who, with Ross Tucker, writes the Science of Sport blog. When you first feel hot you will probably take off some clothing layers, then you'll slow your pace a bit, and finally you'll start to walk or stop entirely and get yourself somewhere cooler, he says. "Your brain and body have pretty good ways of getting you to do what they want you to do, and eventually, it becomes so uncomfortable you'll say, 'I'm out of here,' " he says. (Dugas and Ross have been writing on their blog about heat-related changes in performance.)

There's some not-bad news about childhood obesity today: A study published in the Journal of the American Medical Association finds that the prevalence of kids with a high body mass index, or BMI, showed no significant increase between 1999 and 2006.

If that trend is borne out in data for subsequent years, it's at least a sign that the upward creep of child BMI may have leveled off. But it's by no means great news, since it still means more than 16 percent of kids between 2 and 19 had BMIs at or above the 95th percentile, while about 32 percent were at or above the 85th percentile. I know—that looked weird to me, too: How can 16 percent of kids be above the 95th percentile? (It's like Lake Wobegon, where all the children are above average!) But those percentile charts are based on decades-old data on kids' weight; kids have gotten heavier in proportion to height, so now 16 percent of them are at or above the level that used to be the cutoff for the top 5 percent.

When I feel like my jeans are getting a little tight, I have a no-fail, no calorie-counting, no-angst solution: Cut back on dining out. It's no surprise that it works. Researchers at Cornell University's Food and Brand Lab have found through a host of studies that restaurants are full of environmental cues, from plate size to bread condiments, that encourage us to eat more.

And the food itself is plentiful and often caloric; while New York City is requiring chain restaurants to put calorie counts on menu boards, those may not be accurate everywhere, as an investigation by a group of TV stations showed last week. Their findings: Of 23 "diet" menu items at popular chain restaurants like Chili's and Applebee's, 78 percent contained more fat than they were supposed to, and almost 69 percent had more calories than was indicated on the menu. The Wall Street Journal conducted a similar survey earlier this year and found that while the nutritional information was generally accurate, free add-ons like cheese and bread boosted the meal's calories considerably.

I wrote recently that 100 percent fruit juice, while it's packed with the nutrients lacking in more diluted fruit drinks, is still caloric, so it shouldn't be consumed with impunity. That's true, but there's some good news for parents whose kids prefer their fruit in liquid form: Most kids and teenagers who consume 100 percent juice don't gain weight. Those studies reviewed by researchers that did find a weight gain found it in already overweight kids or adolescent girls.

One caveat is that the studies that were reviewed can't show cause and effect; there might be some other reason these kids didn't gain weight. For example, kids who drink fruit juice rather than soda may be healthier in other regards, too. But the takeaway from this review is that drinking 100 percent fruit juice (we're not talking here about the less nutritious but often equally caloric fruit "cocktails" and other drinks) in moderate amounts is probably not going to make your otherwise healthy kids overweight and may help them meet their nutrient requirements.

That said, fruit is still preferable. It contains fiber, which has its own benefits. (See my earlier post on fruit drinks for the details.) And for a kid or teenager who is already overweight, whole fruit delivers those nutrients with fewer calories. The full study, published in the American Journal of Lifestyle Medicine, is available online here (.pdf) for a limited time.

Stigma can be a powerful force in changing behavior. Just ask smokers, whose once accepted habit is now so marginalized that the prevalence of smoking has dropped to about 19 percent of U.S. adults from nearly 24 percent just a decade ago. A lot of factors figured into the decline since smoking's mid-20th-century peak, but the sense that smoking is disgusting as well as unhealthful and socially costly has certainly contributed to many people's decision to quit.

Now that smokers have been taken care of, the obese are the new scapegoats for a lot of our ills. Last week, a letter published in the Lancet noted that the obese contribute more than their thinner compatriots to food scarcity and global warming, given that they eat more and require more transportation energy to move themselves around. While the authors' intent was probably not to make the obese feel worse, the media translations of the study in my quick Google search turned up headlines such as "Fat People Cause Global Warming, Higher Food Prices" and "Scientists Blame Fat People for Global Warming."

What if you could turn video games, criticized for everything from their obsessive hold on users to their purported role in childhood obesity to their misogynist elements, into something, well, healthy? That's the idea behind "exergaming": physically interactive video games, controllers, and systems that aim to get your heart rate up without making you feel like you're doing penance. This whole emerging discipline is about to get a big bump with the release next week of Nintendo's Wii Fit, which is already flying off the shelves in Asia and Europe and is likely to be in short supply here, too.

Gaming sites and reviewers are weighing in; here's what the New York Times testers had to say, here's how the Wall Street Journal liked the system, and here's how CNET reviewed the game. (Another blogger has a review based on a month of use in Japan.)