The 7 best fat-blasters

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By Su Reid-St. John

We all have days when there's no time to get to the gym. So we wondered: Which close-to-home cardio activities blast fat fastest?

Wonder no more. Here are the top seven fat-and-calorie burners, from Los Angeles based celeb trainer Ramona Braganza, who has helped shape the amazing bodies of stars like Jessica Alba, Halle Berry, and Anne Hathaway.

Try any one of these, and you'll boost your metabolism for up to a whole day afterward. One small workout, one giant payoff.

1. Inline skating
Burns 425 calories in 30 minutes

Surprised? While skating might be so much fun you forget you're actually working out, it's also numero uno on our list when it comes to blasting fat and calories.

The big burn stems from the side-to-side movement of your thigh and butt muscles (demanding more from your body than the straightforward motion of our number-two activity -- running). And your core gets involved in a big way to keep you balanced.

What's more, you get all these benefits without putting too much stress on your knees and other joints. Skate at a strong, steady pace. Don't forget your helmet, wrist guards, and knee and elbow pads.

Boost the burn: Alternate one minute of hard skating with one minute of medium-paced strokes.

Health.com: Get a beautiful butt in 4 weeks

2. Running
Burns 374 calories in 30 minutes

The typical runner's shape is sleek and lean, and there's a reason for that: The major running muscles -- legs, butt, core -- happen to be the biggest calorie-and-fat-burning muscles in your body.

To get the most out of each stride, swing your arms close to your body, don't lean forward, and keep your feet low to the ground. To lessen impact, land on the middle of your foot, then roll through to your toes.

Boost the burn: Alternate fast and slow intervals, or take to the hills.

Health.com: How to run faster

3. Jumping rope
Burns 340 calories in 30 minutes

You knew this workout had to be high on the list. After all, it's one of pro boxers' favorite ways to train.

To get the most from each jump, use a rope with handles that reach to just under your armpits when you stand on the middle of it, and follow these top-form tips: Jump with your feet slightly apart and body upright, and keep your jumps low to the ground. Don't have a rope? You'll get the same benefits by doing the movements rope-free.

Boost the burn: Frequently switch up your speed (slow, fast) and style (jumping with one foot, then two feet), or jump rope while you jog.

Health.com: How to jump the weight off

4. Hula hooping
Burns 300 calories in 30 minutes

There's a reason Marisa Tomei and Beyoncé hoop to keep their bodies beautiful -- it's a major fat-and-calorie torcher. To do it yourself, grab an adult-sized hoop (they're larger and heavier than kids' hoops, making them easier to spin); you'll know you have the right size if it reaches your chest when you stand it up in front of you.

No fancy moves required, either. Simply keep it going around your waist. To start, stand with one foot in front of the other and shift your weight back and forth (versus around in a circle). And don't worry if you're less than perfect at first; you'll still knock off major calories, plus get better every time you spin.

Boost the burn: Get how-tos for advanced moves and a fun workout at Health.com/hula-hoop.

Health.com: Hoop yourself slim

5. Tennis
Burns 272 calories in 30 minutes

Don't think you need to round up a partner or trek all the way to a court to break a super sweat with racket in hand. (Though if you have a pal and a nearby net, you'll burn the same calories.) Simply find a flat area near a wall or garage door that you can hit the ball against.

Alternate forehand and backhand shots -- then see how many you can do in a row without goofing. Stand 10 to 25 feet away, which will force you to hit harder. Even practicing your serve will get your body in burn mode, because you'll have to run and bend to pick up your missed balls.

Boost the burn: Try to hit the ball consistently for 50 or 100 strokes. "Having a goal will make you work harder to reach it," Braganza says.

Health.com: 30-minute workout, no gym required

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6. Dancing
Burns 221 calories in 30 minutes

This may not be the biggest calorie-burner in the bunch, but it's still an excellent -- and fun! -- metabolism booster. (Just look at Kelly Osbourne, who jump-started her amazing 42-pound loss on Dancing with the Stars.)

The key is to keep the tempo high, choosing songs with fast rhythms like Latin or Bollywood, and don't rest between songs.

Try Braganza's favorite trick: Download a workout's worth of your favorite tunes. Begin with an upbeat inspirational song think "Just Dance" by Lady Gaga, then move on to songs with increasingly faster tempos. Slow the beat toward the end to cool down.

Boost the burn: Use your arms! Raise them in the air and move them to the beat.

Health.com: Dance your way to toner abs and legs

7. Walking vigorously
Burns 170 calories in 30 minutes

That's right, walking actually made our list. Full disclosure, though: A leisurely stroll with a friend won't cut it. You should be walking briskly enough that it's difficult to keep up a steady conversation.

To get the most from your biggest calorie-burning muscles -- legs, butt, and core -- take short, quick steps, keep your torso upright, and pump your arms back and forth (not side to side) in time with your stride. With each step, land on your heel and roll through to your toes.

Boost the burn: Alternate two minutes of brisk strides with one minute of as-fast-as-you-can-go walking (or jogging).

Something you should know

5 Scary Cancer Questions, Answered

Q: I can’t always find—or afford—organic produce. How harmful are the pesticides in nonorganic foods?

A: People who consistently eat a diet high in fruit and vegetables have lower cancer risk—whether the produce is organic or not, according to David Katz, M.D., director of the Yale Prevention Research Center in New Haven, Connecticut. That said, Dr. Katz does think it makes sense to keep pesticide exposure to a minimum, because experts aren’t sure how—if at all—it affects cancer risk. About 3 percent of domestic products and 4 percent of imported products had pesticide levels of concern, according to a 2007 FDA report. Some items such as apples, bell peppers and spinach contain higher levels of pesticides than others, possibly because they have more permeable skin or more is taken in through their root systems, so use our shopping list the next time you hit the grocery store for guidance on when it’s best to opt for organic.

Q: I’ve read that sunscreen can actually cause cancer—is that true?

A: Sunscreen is still a must. Period. But controversy flared after a report by the Environmental Working Group claimed that 41 percent of sunscreens contain a form of vitamin A (retinyl palmitate) that may speed the development of skin tumors and lesions when exposed to...sunlight! The American Academy of Dermatology criticized the analysis because the data was from research conducted on mice, and it’s unclear if it’s applicable to humans. Not all sunscreens contain the chemical in question, so if you’re concerned, opt for those made with zinc oxide, titanium dioxide or Mexoryl. Bonus: These ingredients are less likely to break down than others, so the protection lasts longer.

Q: I drink bottled water all the time, but I keep hearing that some bottles contain dangerous chemicals. Should I be worried?

A: In this case, it’s valid to be concerned. BPA, a chemical often found in plastic water and baby bottles and metal cans—even cash register receipts—has been linked to increased risk for breast cancer and heart disease. “BPA acts as a weak estrogen, which can spur the growth of cancerous cells,” says Hugh Taylor, M.D., professor of obstetrics, gynecology and reproductive sciences at Yale University Medical Center. Whenever possible, give plastic water bottles a pass and sip from glass or steel containers instead (I often choose a metal commuter cup); use baby bottles that are labeled BPA-free (fortunately these are widely available); and avoid plastics with the code 7 on the bottom—those are more likely to contain BPA. Also, opt for fresh or frozen foods instead of canned ones (most cans are lined with BPA-epoxy liner), and wash your hands after handling receipts.

Q: Is it true that three bad sunburns guarantees you’ll get skin cancer?

A: Not exactly, but your risk for skin cancer, including melanoma, dramatically increases if you have had five or more severe sunburns that blister. “The more sun exposure you get, the more DNA damage to your skin, which can lead to cancerous changes,” explains Kevin Pinski, M.D., associate professor of dermatology at Northwestern University Medical School. It’s not only burning that puts you at risk. Cumulative exposure ( repeated sunbathing without burning) is linked to basal cell and squamous cell carcinomas. You can’t reverse all your past exposure, but you can prevent future damage: Wear protective clothing (like long sleeves) and get your tan from a tube, not a tanning bed! Remember: The only safe tan is a fake tan.

Q: Cancer rates seem to be skyrocketing—what’s going on?

A: Despite scary headlines, rates of many cancers are going down in this country, Michael Thun, M.D., an epidemiologist at the American Cancer Society in Atlanta, assured us. Breast cancer incidence rates have dropped 11 percent since 1999; experts say that’s because women stopped using hormone-replacement therapy after studies linked it to cancer. Fewer women have had colon cancer over the past two decades thanks to better screening. And ovarian and uterine cancersare less common because women are taking birth control pills for longer periods of time. (The Pill prevents ovulation, which is thought to trigger cell damage and raise the risk for tumors.) More encouraging news: If you do get cancer, you’re more likely to beat it. Breast cancer death rates are down 30 percent, thanks to earlier detection and better treatments. And five-year survival rates for all cancers are up almost 20 percent. With research and advocacy, we can lower those numbers more every day.