By Jené Luciani for Shape.com

These days, it takes more than an apple a day to keep the doctor away. With hectic lifestyles and bad habits like skipping sleep, excess alcohol consumption and sky-high stress levels, it's harder than ever for most people to stay fit and healthy, much less take extra steps to reduce your risk of diseases like cancer, stroke and heart disease.

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That's why Dr. Tiffany Sizemore-Ruiz, author of the blog SizeMoreHeart.com, pulled together a list of 10 simple rules to stay healthy, happy and fit... for life!

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  • Kick The Habit

    Even if you only light up occasionally, you're doing irreparable damage to your body. According to the Centers for Disease Control and Prevention, cigarette smoking kills one in five people in the United States each year, yet it's the most preventable cause of death. "As a doctor, this is one thing I <em>do not ever</em> budge on. This is hands down the worst thing you could ever do to your body," Sizemore-Ruiz says. <em>Flickr photo by <a href="http://www.flickr.com/photos/miss_pupik/864891401/" target="_hplink">miss pupik</a></em>

  • Don't Fake It

    That sun-kissed glow could just be the kiss of death. People who use tanning beds are two-and-a-half times more likely to develop a deadly form of skin cancer than those who don't fake bake. If that's not reason enough to skip the sun beds, you'll also develop premature wrinkles and speed up the aging process of your skin. "You may think it's cute to be tan now, but let me tell you, Botox will not be able to get rid of those wrinkles, and it definitely can't get rid of skin cancer," Sizemore-Ruiz says. This same rule applies to time spent in the sun -- be sure to always wear sunscreen to prevent overexposure.

  • Eat Chocolate

    Surprised by this rule? Believe it or not, you can enjoy the foods you like -- any and all of them, in moderation. "The key to any good diet is to allow yourself a treat every once in a while. If you eat ice cream every day, it doesn't taste nearly as good as if you eat it at the end of the week as a reward for an entire week of healthy eating!" <em>Flickr photo by <a href="http://www.flickr.com/photos/shimelle/338880488/" target="_hplink">shimelle</a></em>

  • Know Your Numbers

    If you don't know your HDL from your LDL, you're doing your body a disservice. "This is a tip from the American Heart Association," Sizemore-Ruiz says. "Knowing your cholesterol and blood sugar levels and having them checked regularly will help you to make more educated decisions about your diet and what your goals are."

  • Exercise Regularly

    The American Heart Association recommends 30 minutes of aerobic exercise five days a week. Are you doing enough? It doesn't mean you have to hit the gym for an intense training session, even a brisk afternoon walk has a positive impact on your physical and mental health. "This is moderate intensity like on the elliptical or Stairmaster, and this is also non-negotiable. It's not just about exercising to look good; this is exercising to keep your heart strong," Sizemore-Ruiz says. <em>Flickr photo by <a href="http://www.flickr.com/photos/unephotos/6497104445/" target="_hplink">UNE Photos</a></em>

  • Get To Know Your DNA

    Did your maternal grandmother have ovarian cancer? Did your father have colon cancer? It pays to know your family history and how it can affect your own health and wellness. "I cannot express how important this is. It can totally change the screening guidelines for you," Sizemore-Ruiz says. "For instance, a screening colonoscopy is done at 50 years old, but if your father had colon cancer at 49, then you must have a screening at 39! Not just cancers, but knowing family history of things like heart disease and diabetes -- and keeping a record of it -- will help your physician make the right decisions for your health."

  • Trade Your Latte For Tea

    Green tea is packed with antioxidants and also has weight-loss properties, so sip away, advises Sizemore- Ruiz. "I try and drink at least one cup a day, but I really aim for two. Green Tea lattes and frappes don't count... but nice try!" <em>Flickr photo by <a href="http://www.flickr.com/photos/softestthing/393232322/" target="_hplink">bokeh burger</a></em>

  • Ditch The Soda

    Soda is not only a diet-spoiler (hello, liquid calories!), it can also have an adverse effect on your health! "I advise patients to never drink regular soda. I'd prefer you not to drink the diet soda either, but if you must have the taste of soda, drink the diet kind. The amount of calories and high fructose corn syrup in regular soda is insane. The best advice is to replace that daily soda fix with some green tea instead." <em>Flickr photo by <a href="http://www.flickr.com/photos/poolie/2474643298/" target="_hplink">poolie</a></em>

  • Get Your Annual Checkup

    Those annual breast exams and pap smears are super important for women of all ages. "I had a 20-something patient die of cervical cancer because she never went for her annual OB/GYN exam. In this day and age, there is almost no reason as to why women should be dying of cervical cancer," Sizemore-Ruiz says. "Also, all women should be doing monthly breast exams (do it at the same time every month, preferably two or three days after your menstruation), as well as an annual mammogram after the age of 40."

  • Leave The Whites To Linens

    When it comes to diet, opt for colorful foods that pack a nutritious punch. You don't have to cut out carbs completely, just opt for the healthy kind. Sizemore-Ruiz suggests "avoiding white rice, white bread, and white pasta like it's the plague" and replacing all "white" foods with their whole-wheat counterpart. "White foods offer almost no nutritional value, and replacing these carbs with whole grains adds vitamins and minerals to your diet." <em>Flickr photo by <a href="http://www.flickr.com/photos/grongar/4433918552/" target="_hplink">grongar</a></em>