Scientists in Boston found that drinking one or more regular or diet colas every day doubles your risk of metabolic syndrome - a cluster of conditions, including high blood pressure, elevated insulin levels, and excess fat around the waist, that increase your chance of heart disease and diabetes. One culprit could be the additive that gives soda its caramel color, which upped the risk of metabolic syndrome in animal studies. Scientists also speculate that soda drinkers regularly expose their tastebuds to natural or artificial sweeteners, conditioning themselves to prefer and crave sweeter foods, which may lead to weight gain, says Vasan S. Ramachandran, MD, a professor of medicine at Boston University School of Medicine and the study's lead researcher.

Better choices: Switch to tea if you need a caffeine hit. If it's fizz you're after, try sparkling water with a splash of juice. By controlling blood pressure and cholesterol levels, preventing diabetes, and not smoking, you can add 6 to 9 1/2 healthy years to your life.

You have strong legs
Lower-body strength translates into good balance, flexibility, and endurance. As you get older, those attributes are key to reducing your risk of falls and injuries - particularly hip fractures, which often quickly lead to declining health. Up to 20% of hip-fracture patients die within 1 year because of complications from the trauma.

"Having weak thigh muscles is the number one predictor of frailty in old age," says Robert Butler, MD, president of the International Longevity Center–USA in New York City. To strengthen them, target your quads with the "phantom chair" move, says Joan Price, author of The Anytime, Anywhere Exercise Book. Here's how: Stand with back against wall. Slowly walk feet out and slide back down until you're in a seated position, ensuring knees aren't beyond toes and lower back is pressed against wall. Hold until your thighs tell you, Enough! Do this daily, increasing your hold by a few seconds each time.

You eat purple food
Concord grapes, blueberries, red wine: They all get that deep, rich color from polyphenols - compounds that reduce heart disease risk and may also protect against Alzheimer's disease, according to the new research. Polyphenols help keep blood vessels and arteries flexible and healthy.

"What's good for your coronary arteries is also good for your brain's blood vessels," says Robert Krikorian, PhD, director of the Cognitive Disorders Center at the University of Cincinnati. Preliminary animal studies suggest that adding dark grapes to your diet may improve brain function. What's more, in a recent human study, researchers found that eating 1 or more cups of blueberries every day may improve communication between brain cells, enhancing your memory

You don't like burgers
A few palm-size servings (about 2 1/2 ounces) of beef, pork, or lamb now and then is no big deal, but eating more than 18 ounces of red meat per week ups your risk of colorectal cancer - the third most common type, according to a major report by the American Institute for Cancer Research. Colorectal cancer risk also rises by 42% with every 3 1/2-ounce serving of processed meat (such as hot dogs, bacon, and deli meats) eaten per day, the report determined. Experts aren't sure why red and processed meats are so harmful, but one of their suspects is the carcinogens that can form when meat is grilled, smoked, or cured - or when preservatives, such as nitrates, are added.

"You can have an occasional hot dog at a baseball game, but just don't make it a habit," says Karen Collins, RD, a nutrition advisor at AICR. And when you do grill red meat, marinate it first, keep pieces small (kebab-size), and flip them often - all of which can help prevent carcinogens from forming. If you're baking or roasting it, keep the oven temp under 400�F.

You really like your friends ...
"Good interpersonal relationships act as a buffer against stress," says Micah Sadigh, PhD, an associate professor of psychology at Cedar Crest College. Knowing you have people who support you keeps you healthy, mentally and physically: Chronic stress weakens the immune system and ages cells faster, ultimately shortening life span by 4 to 8 years, according to one study.

Not just any person will do, however. "You need friends you can talk to without being judged or criticized," says Sadigh.

You embrace the challenge
People who consider themselves self-disciplined, organized achievers live longer and have up to an 89% lower risk of developing Alzheimer's than the less conscientious, according to two studies.

When you're good at focusing your attention, you use more brainpower, says the lead researcher in both studies, Robert S. Wilson, PhD, a professor of neurological sciences and psychology at Rush University Medical Center in Chicago. Set personal or career goals, and challenge yourself to meet them by a certain time. Also, try new things to stimulate your brain: If you always read fiction, pick up an autobiography instead. The next day, try to recall three facts you learned from the reading.

You're a flourisher
About 17% of Americans are flourishers, says a study in American Psychologist. They have a positive outlook on life, a sense of purpose and community, and are healthier than "languishers" - about 10% of adults who don't feel good about them selves. Most of us fall somewhere in between.

"We should strive to flourish, to find meaning in our lives," says Corey Keyes, PhD, a professor of sociology at Emory University. "In Sardinia and Okinawa, where people live the longest, hard work is important, but not more so than spending time with family, nurturing spirituality, and doing for others."