Your metabolism is partly ruled by genetics, but you can rev it up naturally by eating right. Fill up on the following nine foods and beverages to increase your body's fat-burning power. 
A study published in Physiology & Behavior found that the average metabolic rate of people who drank caffeinated coffee was 16% higher than that of those who drank decaf. 
Egg whites are rich in branched-chain amino acids, which keep your metabolism stoked, says Chicago nutritionist David Grotto. Eggs are also loaded with protein and vitamin D. 
Lean meat is full of iron; deficiencies in the mineral can slow metabolism. Eat three to four daily servings of iron-rich foods, such as chicken or fortified cereal. 
If you're even mildly dehydrated, your metabolism may slow down, says Dr. Scott Isaacs, clinical instructor of medicine at the Emory University School of Medicine. Tip: Drink water cold, which forces your body to use more calories to warm it up. Health.com: 15 foods that help you stay hydrated 
Chili peppers contain capsaicin, a chemical compound that can kick metabolism into higher gear, Isaacs says. He suggests adding a tablespoon of chopped chili peppers to a meal once a day. Chili peppers are also an unexpected source of vitamin C. 
The brew contains a plant compound called EGCG, which promotes fat-burning, research suggests. 
Studies conducted by Michael Zemel, former director of The Nutrition Institute at the University of Tennessee, suggest that consuming calcium may help your body metabolize fat more efficiently.Health.com: 15 weird things linked to heart attacks 
Whole grains help your body burn more fat because they take extra effort to break down than processed grains, like white bread and pasta. Whole foods that are rich in fiber, like brown rice and oatmeal are your best bets. 
About 20% of women are iron deficient, which is bad news for your waistline -- your body can't work as efficiently to burn calories when it's missing what it needs to work properly. One cup of lentils provides 35% of your daily iron needs. - Drinking coffee before a workout can help burn more calories
- Other benefits include increased circulation, better memory and less post-workout pain
- Don't overdo it, dietician says, and drink plenty of water
Editor's note: Registered dietician Cynthia Sass is Health magazine's contributing nutrition editor.
(Health.com) -- Half of Americans start their day with coffee, and according to recent study, working out after downing a cup of java may offer a weight-loss advantage.
The Spanish study, published in the International Journal of Sport Nutrition and Exercise Metabolism, found that trained athletes who took in caffeine pre-exercise burned about 15% more calories for three hours post-exercise, compared to those who ingested a placebo.
The dose that triggered the effect was 4.5 mg of caffeine per kilogram of body weight. For 150-pound woman, that's roughly 300 mg of caffeine, the amount in about 12 ounces of brewed coffee, a quantity you may already be sipping each morning.
If you've always thought of coffee as a vice -- one you're simply not willing to give up -- you'll be happy to know that it's actually a secret superfood. And if you exercise, caffeine can offer even more functional benefits for your workouts.
Here are five more reasons to enjoy it as part of an active lifestyle, along with five "rules" for getting your fix healthfully.
Health.com: 12 surprising sources of caffeine
Improved circulation
Recent Japanese research studied the effects of coffee on circulation in people who were not regular coffee drinkers. Each participant drank a 5-ounce cup of either regular or decaffeinated coffee. Afterward, scientists gauged finger blood flow, a measure of how well the body's smaller blood vessels work.
Those who downed "regular" (caffeinated) coffee experienced a 30% increase in blood flow over a 75-minute period, compared to those who drank the "unleaded" (decaf) version. Better circulation, better workout -- your muscles need oxygen!
Less pain
Scientists at the University of Illinois found that consuming the caffeine equivalent of two to three cups of coffee one hour before a 30-minute bout of high-intensity exercise reduced perceived muscle pain. The conclusion: caffeine may help you push just a little bit harder during strength-training workouts, resulting in better improvements in muscle strength and/or endurance.
Health.com: 15 natural back pain remedies
Better memory
A study published this year from Johns Hopkins University found that caffeine enhances memory up to 24 hours after it's consumed. Researchers gave people who did not regularly consume caffeine either a placebo, or 200 mg of caffeine five minutes after studying a series of images. The next day, both groups were asked to remember the images, and the caffeinated group scored significantly better.
This brain boost may be a real boon during workouts, especially when they entail needing to recall specific exercises or routines.
Muscle preservation
In an animal study, sports scientists at Coventry University found that caffeine helped offset the loss of muscle strength that occurs with aging. The protective effects were seen in both the diaphragm, the primary muscle used for breathing, as well as skeletal muscle. The results indicate that in moderation, caffeine may help preserve overall fitness and reduce the risk of age-related injuries.
Health.com: 14 reasons you're always tired
More muscle fuel
A recent study published in the Journal of Applied Physiology found that a little caffeine post-exercise may also be beneficial, particularly for endurance athletes who perform day after day.
The research found that compared to consuming carbohydrates alone, a caffeine/carb combo resulted in a 66% increase in muscle glycogen four hours after intense, glycogen-depleting exercise. Glycogen, the form of carbohydrate that gets stockpiled in muscle, serves as a vital energy "piggy bank" during exercise, to power strength moves, and fuel endurance.
Packing a greater reserve means that the very next time you work out, you've upped your ability to exercise harder and/or longer.
Health.com: 11 ways to boost your energy with food
But this news doesn't mean you should down as much coffee as possible -- your good intentions may backfire. In my work with athletes, I recommend five basic rules to best reap caffeine's rewards:
Don't overdo it. The maximum amount of caffeine recommended for enhancing performance with minimal side effects is up to 6 mg per kg body weight, which is about 400 mg per day (or about 16 ounces of coffee) for a 150-pound woman.
Incorporate it in healthy ways. Doctor up coffee with almond milk and cinnamon instead of cream and sugar, or whip coffee or tea into a fruit smoothie, along with other nutrient-rich ingredients like almond butter and oats or quinoa.
Be consistent with your intake. Research shows that when your caffeine intake is steady, your body adjusts, which counters dehydration, even though caffeine is a natural diuretic. In other words, don't reach for two cups one day and four the next.
Keep drinking good old H2O, your main beverage of choice.
Nix caffeine at least six hours before bed to prevent sleep interference, and listen to your body. If you're relying on caffeine as an energy booster because you're tired, get to the root of what's causing fatigue. Perhaps it's too little sleep, overexercising, or an inadequate diet. If something's off kilter, you won't see progress, and you'll likely get weaker rather than stronger. Striving for balance is always key!
Copyright Health Magazine 2011
