Interactive Tool: When Are You Most Fertile?

What does this tool measure?

This interactive tool estimates your peak fertility period, also known as your "fertile window." This is when you are most likely to get pregnant. Do not use this tool to prevent pregnancy.

To find your peak fertility period, the tool first calculates the day you are most likely to ovulate. This is the day an ovary releases an egg. On the tool, you will enter the typical length of your menstrual cycle, and you will click on the first day of your last menstrual period.

• To know how long your cycles are, track the number of days on a calendar for 2 or 3 months or cycles. Your menstrual cycle begins with the day your period starts and ends the day before your next period starts.
• If you do not know the number of days in your menstrual cycle, you can use 28 days. This is the average length of a menstrual cycle. But if your cycle is longer or shorter than that, or if it is not always the same length, this tool will not predict your fertile window very well.

This calculator is meant to give you a rough estimate. Women usually ovulate at day 15, but it's also normal to ovulate well before or after the 15-day mark.

For information about reading your body's signs to tell when you will ovulate, see Fertility Awareness.

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	Fertility calculator

What do the results tell me?

Your "fertile window" is up to 6 days long, once a month. It includes:

• The day you ovulate. This is when you have the best chance of becoming pregnant. (A human egg usually lives for only 12 to 24 hours after ovulation. This is why you are not likely to get pregnant by having sex a day after you ovulate.)
• The 5 days before ovulation. This is because sperm can live in a woman's body for 3 to 5 days after sex. When an egg is released, one of these sperm is ready to fertilize it.

If you are planning a pregnancy, do not have sex during the 5 days before your 6-day fertile window. (Not ejaculating for a few days helps build up a man's sperm count.) Then have sex once each day of your fertile window, including ovulation day.

What's next?

If your periods are irregular, this calculator is not a good way to predict your ovulation dates. Do not use this tool to prevent pregnancy. For more information, see the topics Fertility Awareness, Pregnancy, and Fertility Problems. If you are looking for information on birth control, see the topic Birth Control.

Source: Stanford JB, et al. (2002). Timing intercourse to achieve pregnancy: Current evidence. Obstetrics and Gynecology, 100(6): 1333–1341.

Why Sleeping is (Almost) More Important Than Breathing

I used to pull all-nighters back in college, forcing myself to stay awake to cram for an exam or finish a paper on art history, my major. I did it because I thought it would help me get ahead, but in the end it always set me back—I wound up tired, cranky and unproductive the next day.

Even though I've grown up (and wisened up) since then, I still have trouble convincing myself to crawl into bed at night: I keep a running tally of all the things I haven't crossed off my to-do list—reading manuscripts, prepping for a TV appearance, even laundry! And I'm always tempted to stay up just a bit longer to get everything done before morning.

So what stops me from burning the midnight oil? Not only has personal experience proved that I'll be more stressed (not to mention less chipper) when I'm sleep-deprived, but studies suggest that not getting adequate zzz's can increase your risk for heart disease and depression, and even cause weight gain (ever found yourself heading to the fridge or the vending machine when you're tired? I have!).

Try these tips to help relax before you hit the sack:

Unplug
Avoid having long conversations on your cell phone before bed: Researchers at Wayne State University in Detroit found that people who were exposed to the slight radiation that emanates from cell phones took longer to fall asleep and spent less time in the deep stages of slumber.
Make Your Bedroom a Haven
Draw the blinds and turn on a fan or a soothing CD of nature noises to block out distracting sounds. Swapping ordinary bedroom bulbs for yellow ones (GE makes a 25-watt version sold at drugstores) can help you feel more tranquil as you're getting ready to nod off. Consider treating yourself to a cozy new comforter or putting flowers on your nightstand so that being in your bedroom—and sleeping!—becomes something you look forward to.
Say Thanks
Once you're under the covers, take two minutes to reflect on the things you're grateful for. Studies show that practicing grateful thinking makes people more optimistic. And going to sleep with happy thoughts will help you sleep more soundly.
Share your favorite relaxing bedtime rituals on SELF's Trade Happiness Tips forum.

6 Fat-Melting Food Swaps

Not all burgers are created equal. That's important, especially when you consider that the average American will consume 100 of them this year.

Take, for example, America's two most famous burgers: the Whopper with Cheese and the Big Mac. A fair fight, right? Well, if you go for the Arch alternative, you'll save 220 calories over the BK Behemoth. (A Big Mac has 540 calories and 29 grams of fat, compared to the Whopper's 760 calories and 47 grams of fat!)

Use that strategy for every burger you eat in 2008, and you'll save 22,000 calories - the equivalent of almost six pounds of body fat. You don't have to (nor should you) live on Big Macs; pick an even leaner burger and save even more.

See, the way you pick your favorite fixes - from burgers to banana splits - could help you make the transition from chubby to chiseled. In researching our new book Eat This, Not That!, we found that the most effective weight-loss strategy doesn't require you to abandon the foods you love, but simply to make better choices when selecting them.

Supplement that approach with plenty of fresh produce and lean protein throughout the week, and you'll trade failed diets and wild weight fluctuations for healthy eating patterns and a lean, new you. And once you learn how it's done, you can stay that way forever. Who wouldn't make that swap?

Pizza
Eat This:
2 slices Domino's large cheese pizza with crunchy thin crust
360 calories
19 g fat

Not That!
2 slices Pizza Hut large cheese pizza with thin 'n cripsy crust
560 calories
24 g fat

Save 200 calories and 5 grams of fat!

In the world of mass-produced pizza, nothing beats Domino's crunchy thin-crust pie. Eat pizza just once a week, and you'll save more than 10,000 calories this year - which is a nice down payment on a smaller waist size.

Turkey Sandwich
Eat This:
Subway 6-inch Turkey Sub with provolone cheese
330 calories
8.5 g fat

Not That!
Panera Bread Sierra Turkey
840 calories
40 g fat

Save 510 calories and 31.5 grams of fat!

Don't sweat the meat in the sandwich: turkey, roast beef, and ham are all lean cuts. But Panera slathers its turkey with a thick layer of chipotle mayo and slides it into a heavy, oily wedge of focaccia, so that turkey is a porker. A Subway 6-incher not enough to quell your raging lunchtime hunger? Double up on meat for just 50 calories more.

Cinnamon Roll
Eat This:
Au Bon Pain Cinnamon Roll
350 calories
21 g sugars
12 g fat

Not That!
Cinnabon Classic Cinnamon Roll
813 calories
55 g sugars
32 g fat

Save 463 calories, 34 grams of sugars, and 20 grams of fat!

OK, there's absolutely no nutritional value in a cinnamon roll. We said it. But when you just have to have one, take comfort in knowing that Au Bon Pain's restrained rendition more than halves the calories, sugar, and fat found in the Cinnabon catastrophe.

Beer
Drink This:
Guinness Draught
125 calories
10 g carbohydrates

Not That!
Sierra Nevada Pale Ale
175 calories
15 g carbohydrates

Save 50 calories a beer!

Surprised? Most people think of Guinness as a beer milkshake: dark, thick, and rich enough to inspire guilt at first sip. But switch out a six-pack a week and you've just saved yourself more than four pounds this year. Extend those savings even further with Beck's Premier Light: At 64 calories a bottle, it doesn't get any lighter than this.

Doughnut
Eat This:
Dunkin' Donuts Glazed Donut
230 calories
10 g fat
12 g sugars

Not That!
Dunkin' Donuts Glazed Cake Donut
330 calories
18 g fat
18 g sugars

Save 100 calories and 8 grams of fat!

Both are cloaked in sugar, but their original doughnuts are light and airy because they're made with yeast, and cake donuts are heavy and dense because they're made with cake batter. Remember: Cake is not a breakfast food.

Fruit Smoothie
Eat This:
Jamba Juice Power Mega Mango Smoothie
420 calories
97 g sugars

Not That!
Dunkin' Donuts Large Tropical Fruit Smoothie
720 calories
142 g sugars

Save 300 calories and 45 grams of sugars!

This sickeningly sweet concoction from Dunkin' has an ingredient list straight out of a chem lab and more sugar than seven Häagen-Dazs vanilla-and-almond ice-cream bars. So this tropical excursion will be bad for your equator. The Jamba version is 100 percent fruit, so there's a huge caloric discount and big antioxidant payload.

For nine more shocking swaps that will help you save big this year, click here.

6 Health Foods That Aren't

Healthy food may be making you fat.

Hold on: I'm not talking about broccoli and bell peppers here. I'm talking about a lot of the foods that are sold to us as "low-fat," "low-carb," or otherwise "healthy" fare. The food industry invests $30 billion a year in advertising, and much of that is used to dupe consumers into believing bogus bites are somehow good for us.

The truth is, behind every low-fat label and celebrated salad is a list of ingredients that would give even the most relentless glutton reason to reconsider.

In researching the best-selling book "Eat This, Not That!," the title for this new blog with my co-author Matt Goulding, we were shocked to find that the foods so many health-conscious eaters in this country consider to be smart choices are actually the most responsible for our ever-expanding waistlines.

Many of the "low-fat" or otherwise "healthy" options we examined packed several hundred extra calories in them! Translation: Get duped into eating one pseudo-healthy food a day, and you'll have an extra 30 pounds (or more) to work off by the end of the year.

We've identified six of the most misunderstood foods in America, so that next time you think you're doing your body a favor, you actually will be - by looking for something else that actually is healthy.

1. Bran Muffin
440 calories
23 grams of fat
35 g sugars

Made primarily with sugar, refined flour and hydrogenated oil, it's like starting your day with a candy bar. Actually, it's like starting your day with two candy bars, since this misunderstood muffin has more fat and calories than two Kit Kat bars.

2. Chicken Caesar Salad
900 calories
60 grams of fat

Caesar salads suffer the consequences of two natural disasters: a flood of fatty dressing and a blizzard of Parmesan cheese and croutons. All told, it's a caloric catastrophe - equal to scarfing down 20 Chicken McNuggets!


3. Tuna Melt
950 calories
55 grams of fat

Plain tuna out of the can is healthy; tuna drenched in mayo, shrouded in melted cheese, and slicked with another layer of dressing is not. You'd be better off eating three six-inch roast beef sandwiches from Subway!

4. Chicken Wrap
700 calories
35 grams of fat

How wraps got such a good rap is beyond us, since they're really just oversized tortillas, packing up to 400 calories on their own - that is, before the onslaught of cheese, meat, and dressing it houses! You'd get the same number of calories from 20 strips of bacon.

5. Turkey Burger
850 calories
50 grams of fat

At home a turkey burger might be a decent choice, but in the restaurant world it means high-fat ground turkey, heavy mayo, melted cheese, and a big, pillowy bun. It's the equivalent of three 8-oz sirloin steaks.

6. Fruit Smoothies
600 calories
120 grams of sugar

Unless it says 100 percent fruit, your "fruit" smoothie is likely made with ice cream, sugar, high fructose corn syrup, and a few token chunks of banana. All told, this popular afternoon snack has as much sugar as six Haagen Dazs Vanilla and Almond ice cream bars. Ouch.

For even more 'healthy' foods that actually expand your waistline, check out these other surprising foods.

20 Saltiest Foods in America

Salty food may seem like the least of your worries, especially if you're among the 40 percent of people who mindlessly shake salt on every dish. An extra dash here, a few sprinkles there — what's the big deal?

A lot, when you consider some of the shocking stats and shady food industry practices we've uncovered. A mere teaspoon of salt contains all 2,300 milligrams (mg) of your recommended daily allotment, yet daily salt consumption is on the rise in the United States — from 2,300 mg in the 1970s to more than 3,300 mg today.

And according to Monell Chemical Senses Center researchers, 77 percent of that sodium intake comes from processed-food purveyors and restaurants. Their motivation: Pile on the salt so we don't miss natural flavors and fresh ingredients.

Why is that a problem? With ever-expanding portion sizes, supersalty foods are displacing fresh fruits and vegetables, which are rich in potassium. And a 1:2 ratio of dietary salt to potassium is critical for your health. Studies show that a high-sodium, low-potassium diet is linked to a host of maladies, including high blood pressure, stroke, osteoporosis, and exercise-induced asthma.

To protect your heart, your bones, your muscles, and your tastebuds, we scoured takeout menus and supermarket shelves to expose the 20 saltiest foods in America. No need to take the information with a grain of salt. These dishes provide plenty.

Saltiest Kids Food
Cosi Kid’s Pepperoni Pizza
2,731 mg sodium
911 calories
43 g fat
112 g carbohydrates

We’ve seen some fuzzy math in the past few months concerning this Cosi catastrophe, with the sodium count changing literally overnight from 6,405 mg sodium to the current number. We’ve tried to sort this out with the Cosi people, but have gotten little hope clarifying the sudden shift. One thing is clear, though: Even if we give them the benefit of the doubt, a pizza with 2,731 milligrams of sodium and 911 calories is the last thing you should be serving your kid.

Saltiest "Healthy" Food
Chili's Guiltless Grill Chicken Platter
2,780 mg sodium
590 calories
85 g carbohydrates

Beware the bait and switch. Many restaurants and packaged-food producers advertise their dishes as being low in calories and fat, only to jack up the sugar and salt content. Case in point: This platter actually has more sodium than Chili's 1,890-calorie Country Fried Steak with sides, toast, and gravy. Stick with the Guiltless Salmon, the best choice on Chili's sometimes-healthy special menu.

Saltiest Frozen Dinner
Swanson Hungry-Man XXL Roasted Carved Turkey
4,480 mg sodium
1,360 calories
70 g fat

Yes, the nutrition data on the back suggests that the package contains two servings, but the label proudly proclaims the 1 1/2 pounds inside, and besides, how many people are going to share their frozen dinner?

Saltiest Sandwich
Quiznos Turkey Bacon Guacamole Large Sub with Cheese and Reduced-Fat Ranch Dressing
4,670 mg sodium
1,120 calories
49 g fat
116 g carbohydrates

First, skip the large sandwich. At Quiznos, few come in under 1,000 calories and 3,000 mg sodium. Next, abandon mozzarella for Swiss, which has a tenth of the sodium. Finally, choose one of the low-calorie subs at Quiznos — the Tuscan Turkey, or better yet, the Honey Bourbon Chicken.

Saltiest Salad
Romano's Macaroni Grill Chicken Florentine
5,460 mg sodium
840 calories
53 g fat

Salads are often the biggest blood-pressure boosters on the menu, since the innocent leaves play perfect host to a flurry of briny toppings and dangerous dressings. Here, salt-laden olives, capers, and Parmesan collide with Macaroni Grill's massive portions and its cooks' affinity for the saltshaker. The only reasonable insalata on the menu is the Mozzarella alla Caprese: It has 450 calories and 760 mg sodium.

Saltiest Appetizer

Papa John's Cheesesticks with Buffalo Sauce
6,700 mg sodium
2,605 calories
113 g fat
296 g carbohydrates

If you were to split this appetizer with two friends, you'd still be close to downing your daily sodium allowance before you even reach for the pizza. Each stick packs the same amount of sodium as a small slice of cheese pizza, and that's without dipping. Your best bet? Cheese pizza. Thin crust.

The Saltiest Dish in America

Romano's Macaroni Grill Chicken Portobello
7,300 mg sodium
1,020 calories
66 g fat

With three items on our top 20 list, plus a slew of dishonorable mentions, Macaroni Grill earns its title as America's saltiest chain restaurant. But what makes this the saltiest dish in America? One word: demi-glace, a fancy French name for the viscous salt slick that blankets this disastrous dish. You would have to eat 32 cups of potassium-rich broccoli to compensate for this sodium avalanche.

For a complete list of the 20 Saltiest Foods in America, and details on how to disarm the restaurant industry's weapons of mass construction, check out these rankings and nutrition secrets.

Is This the Worst Drink on the Planet?

Recently, while poring over some research, I got a breathless call from my co-author buddy, Matt. “You won’t believe what I just found! Check this out.”

He sent me a link to a Baskin Robbins page, and what came up on my screen (gory details below - straight from their website) was a tower of nutritional insanity unmatched by any other beverage we’ve come across in our years of research.

“Instead of giving Socrates hemlock, they should have just forced him to drink one of these,” he said. “Could this 2,300-calorie liquid monstrosity be the worst drink on the planet?” We've seen a few 1000-calorie shakes, but this is twice as bad as anything we've ever seen.

The menu description may sound simple enough: “A blend of HEATH Bar Crunch and Jamoca® ice creams, chopped HEATH Bar pieces and caramel, topped with whipped cream and chopped HEATH Bar pieces.” But the ingredient list reveals a much more complicated story. Methyl paraben, propylene glycol, polysorbate 80: You’d need a degree in chemical engineering just to have a shot at cracking this brain-freezing code. All told, the list of ingredients runs seven inches and 73 ingredients long. Whatever happened to the days when a milkshake was just ice cream and milk?

As unsavory as this list of indecipherable emulsifiers, preservatives, and artificial flavorings may be, the most concerning part comes when you consider the sheer nutritional impact of this weapon of mass construction.

To give you some perspective, slurping up one 32-ounce Heath Shake is the caloric equivalent of eating 12 Krispy Kreme doughnuts, the saturated fat equivalent of scarfing 60 slices of bacon, and will give you the same sugar rush as working your way through 13 Haagen Dazs Vanilla and Almond ice cream bars.

The drink is part of Baskin Robbins “candy-bar madness” promotion — a deal struck with Hershey’s to any dairy derivative they can get their hands on with bite-size chunks of popular candies.

We put in a call to the company to check in on the product. They called us back to say they were discontinuing it at the end of May. For some tasty swaps for high-fat and high-calories drinks, click here.

And if you have your own list of food bombs, please add them in the comments section. Believe me, the food manufacturers are listening — and your opinion does matter.

Belt-Busting Beverages

My buddy, Bill, came to me a while back looking for advice on how to banish the bulging belly he had acquired in his later years. I skipped the diet lecture and instead gave him a copy of the book, Eat This, Not That!, and a single piece of advice: Start with the drinks chapter.

Four months later, Bill has adopted the simple food swap philosophy and dramatically altered his calorie intake without giving up the foods and drinks he loves. His reward: 25 pounds and three inches off of his waistline — in around six weeks!

I told Bill to start with beverages because between soda, coffee drinks, smoothies, and booze, he was sipping away more than a quarter of his daily calories. He’s not the only one. A study from the University of North Carolina found that we consume 450 calories a day from beverages, nearly twice as many as 30 years ago! This increase amounts to an extra 23 pounds a year that we're forced to work off — or carry around with us.

There’s good news and bad news when it comes to liquid calories. The bad news is they are the most difficult calories for us to gauge, because we have none of the greasy, cheesy visual cues we get when we go face-to-face with a plate of loaded nachos or a triple cheeseburger. The good news is that they are the easiest calories to cut from your diet. Just ask Bill.

I've identified the most bloating beverages in gas stations, bars, smoothie counters, and coffee shops across America and replaced them with sensible and satisfying stand-ins for a fraction of the caloric cost. So you can sip what you want, skip the diet, and still lose lots of weight this year.


Coffee Drink

Drink This:
Double Espresso Macchiato
15 calories
0 g fat

Not That!
Large Caffe Latte
190 calories
7 g fat

In the hierarchy of espresso drinks, lattes sit squarely at the bottom. That's because they're more milk than java, and are susceptible to huge pumps of sugary syrup from eager-to-please baristas. A macchiato gives the same caffeine kick for a tiny fraction of the caloric cost by swapping out the excess steamed milk for a thick crown of frothed milk. It's a simple but meaningful switch for caffeine junkies looking for a healthier fix.

Lunchbox Drinks for Kids

Drink This:
Minute Maid Fruit Falls Tropical (1 pouch)
5 calories
1 g sugars

Not That!
Capri Sun Pacific Cooler (1 pouch)
100 calories
26 g sugars

Make this switch in the little ones' lunchboxes every day of the school year, and you'll cut 25 cups of sugar — enough to make 1,600 chocolate chip cookies — from their diet. But, still, I have to give Capri some credit: They recently announced that beginning this spring, they’ll be cutting the sugar and calorie content of their namesake beverage by 25 percent.

When asked why, a Capri Sun rep said that parents more than ever are looking for healthier choices that their kids will like. I couldn’t agree more, and it’s hopefully the beginning of an important sea change in the types of foods and beverages companies market to our kids.

Blended Fruit Drink

Drink This:
Krispy Kreme Very Berry Chiller (20 oz)
290 calories
71 g sugars

Not That!
Starbucks Venti Strawberries and Creme Frappuccino Blended Creme (20 oz)
750 calories
120 g sugars

Let’s get one thing straight: Neither of these are the healthy, fruit-based beverages they may masquerade as. Little to no fruit goes into either of these, and in the case of the Starbucks Frappuccino, this drinkable disaster contains as much sugar as four Snickers bars. The Krispy Kreme Chiller proves to be a more reasonable indulgence, with little of the excessive added sugar or whipped cream that plague most blended "fruit" drinks.

Iced Tea

Drink This:
Honest Green Dragon Tea (16 oz)
60 calories
10 g sugar

Not That!
Arizona Iced Tea (16 oz)
200 calories
25 g sugar

Arizona Tea is a closer relative of the soft drink than the steeped beverage you read about in all of those health studies. That's because the beverage barons of Arizona have a heavy hand with the sugar, all but canceling out any of tea's formidable nutritional benefits. And in a recent analysis conducted by Men's Health, we found that Honest Tea packs more than six times the amount of metabolism-spiking, disease-fighting catechins as the Arizona calorie bomb.

For an entire list of the very best beverages for quick and easy weight loss, click here.

Five Easy Ways to Go Organic

Switching to organic is tough for many families who don’t want to pay higher prices or give up their favorite foods. But by choosing organic versions of just a few foods that you eat often, you can increase the percentage of organic food in your diet without big changes to your shopping cart or your spending.

The key is to be strategic in your organic purchases. Opting for organic produce, for instance, doesn’t necessarily have a big impact, depending on what you eat. According to the Environmental Working Group, commercially-farmed fruits and vegetables vary in their levels of pesticide residue. Some vegetables, like broccoli, asparagus and onions, as well as foods with peels, such as avocados, bananas and oranges, have relatively low levels compared to other fruits and vegetables.

So how do you make your organic choices count? Pediatrician Dr. Alan Greene, whose new book “Raising Baby Green” explains how to raise a child in an environmentally-friendly way, has identified a few “strategic” organic foods that he says can make the biggest impact on the family diet.

1. Milk: “When you choose a glass of conventional milk, you are buying into a whole chemical system of agriculture,'’ says Dr. Greene. People who switch to organic milk typically do so because they are concerned about the antibiotics, artificial hormones and pesticides used in the commercial dairy industry. One recent United States Department of Agriculture survey found certain pesticides in about 30 percent of conventional milk samples and low levels in only one organic sample. The level is relatively low compared to some other foods, but many kids consume milk in large quantities.

2. Potatoes: Potatoes are a staple of the American diet — one survey found they account for 30 percent of our overall vegetable consumption. A simple switch to organic potatoes has the potential to have a big impact because commercially-farmed potatoes are some of the most pesticide-contaminated vegetables. A 2006 U.S.D.A. test found 81 percent of potatoes tested still contained pesticides after being washed and peeled, and the potato has one of the the highest pesticide contents of 43 fruits and vegetables tested, according to the Environmental Working Group.

3. Peanut butter: More acres are devoted to growing peanuts than any other fruits, vegetable or nut, according to the U.S.D.A. More than 99 percent of peanut farms use conventional farming practices, including the use of fungicide to treat mold, a common problem in peanut crops. Given that some kids eat peanut butter almost every day, this seems like a simple and practical switch. Commercial food firms now offer organic brands in the regular grocery store, but my daughter loves to go to the health food store and grind her own peanut butter.

4. Ketchup: For some families, ketchup accounts for a large part of the household vegetable intake. About 75 percent of tomato consumption is in the form of processed tomatoes, including juice, tomato paste and ketchup. Notably, recent research has shown organic ketchup has about double the antioxidants of conventional ketchup.

5. Apples: Apples are the second most commonly eaten fresh fruit, after bananas, and they are also used in the second most popular juice, after oranges, according to Dr. Greene. But apples are also one of the most pesticide-contaminated fruits and vegetables. The good news is that organic apples are easy to find in regular grocery stores.

For a complete list of Dr. Greene’s strategic organic choices, visit Organic Rx on his website.

Patterns: Heavy Burden for Infants Who Lack Sleep

Infants who do not get enough sleep may have an increased risk for being overweight in childhood, a new study suggests.

Researchers recorded the sleep habits of 915 children at ages 6 months, 1 year and 2 years, using questionnaires and in-person interviews. At each visit, they recorded the infants’ length and weight and had parents report on the number of hours their children watched television or videos.

The study, published on Monday in The Archives of Pediatrics and Adolescent Medicine, found that the more sleep infants got, the less likely they were to be overweight at age 3. Infants who slept less than 12 hours a day had double the risk of being overweight compared with children who slept more, and the effect was especially apparent in children who also watched more than two hours of television a day.

The relationship held after adjusting for birth weight, the mother’s age and body mass, breast feeding duration and other variables. The authors say this is the first study to report an association between infant sleep time and children’s being overweight.

What’s a parent to do? “Most important is to practice good sleep hygiene techniques,” said Dr. Elsie M. Taveras, the lead author and an assistant professor of pediatrics at Harvard, who is herself the mother of an infant and a toddler. “No TV in the bedroom, no caffeinated drinks and so on. Getting a good night’s sleep is not just to be at our best the next day; it’s really to assure good health.”

Memory Training Shown to Turn Up Brainpower

A new study has found that it may be possible to train people to be more intelligent, increasing the brainpower they had at birth.

Until now, it had been widely assumed that the kind of mental ability that allows us to solve new problems without having any relevant previous experience — what psychologists call fluid intelligence — is innate and cannot be taught (though people can raise their grades on tests of it by practicing).

But in the new study, researchers describe a method for improving this skill, along with experiments to prove it works.

The key, researchers found, was carefully structured training in working memory — the kind that allows memorization of a telephone number just long enough to dial it. This type of memory is closely related to fluid intelligence, according to background information in the article, and appears to rely on the same brain circuitry. So the researchers reasoned that improving it might lead to improvements in fluid intelligence.

First they measured the fluid intelligence of four groups of volunteers using standard tests. Then they trained each in a complicated memory task, an elaborate variation on Concentration, the child’s card game, in which they memorized simultaneously presented auditory and visual stimuli that they had to recall later.

The game was set up so that as the participants succeeded, the tasks became harder, and as they failed, the tasks became easier. This assured a high level of difficulty, adjusted individually for each participant, but not so high as to destroy motivation to keep working. The four groups underwent a half-hour of training daily for 8, 12, 17 and 19 days, respectively. At the end of each training, researchers tested the participants’ fluid intelligence again. To make sure they were not just improving their test-taking skills, the researchers compared them with control groups that took the tests without the training.

The results, published Monday in The Proceedings of the National Academy of Sciences, were striking. Although the control groups also made gains, presumably because they had practice with the fluid intelligence tests, improvement in the trained groups was substantially greater. Moreover, the longer they trained, the higher their scores were. All performers, from the weakest to the strongest, showed significant improvement.

“Intelligence has always been considered principally an immutable inherited trait,” said Susanne M. Jaeggi, a postdoctoral fellow in psychology at the University of Michigan and a co-author of the paper. “Our results show you can increase your intelligence with appropriate training.”

Why did the training work? The authors suggest several aspects of the exercise relevant to solving new problems: ignoring irrelevant items, monitoring ongoing performance, managing two tasks simultaneously and connecting related items to one another in space and time.

No one knows how long the gains will last after training stops, Dr. Jaeggi said, and the experiment’s design did not allow the researchers to determine whether more training would continue to produce further gains.

By NICHOLAS BAKALAR