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HPRC Fitness Arena: Nutrition
There’s an old adage you may have heard: “Eat after eight, put on weight.” And maybe you’ve experienced it first-hand: You noticed that eating those late night pizzas and ice cream really packed on the pounds. But was your weight gain due to timing or just the high calorie counts? According to research in the field of circadian rhythms (CRs)—the 24-hour cycle of your body’s biological, hormonal, and behavioral patterns—it seems that when you eat could be just as important to weight gain as what you eat.
Deep within your brain sits a small cluster of nerve cells—a “master clock” of sorts—that’s responsible for orchestrating your CRs. Each biological system in your body works on a different CR schedule, and the master clock keeps all the schedules in sync. For example, CRs influence your body’s production of the hormones that regulate hunger, as well as how your body uses and stores fats and sugar, ultimately influencing your body weight, performance, and overall health. Other hormones, such as the ones that tell you when you’re full, are switched on or off according to a variety of inputs.
The two greatest influences on how well your master clock is able to keep things in sync are light and food. Light tells your brain how much sleep you get (think: eyes closed, less light). Food (smell, taste, and consumption) tells your body to produce a myriad of chemicals. As a result, staying up late at night, working shifts, and eating at all hours of the day and night—whether voluntarily or due to the demands of overseas deployments, training demands, shift-work schedules, and even parenthood—can play havoc with your circadian rhythms.
In an interesting twist, not only do CRs influence hunger and body weight, but excess body fat and/or a high-fat diet may disrupt CRs. This can lead to further weight gain, culminating in a collection of health problems known as “metabolic syndrome.” In the U.S., regular loss of sleep closely parallels the occurrence of metabolic syndrome. In addition, researchers have found that people who sleep less or have poor-quality sleep are more likely to become obese.
What to do? Make a conscious effort to “normalize” your daily routines as much as possible to maintain regular mealtimes. Whether you choose to eat three regular-sized meals or four to six smaller meals a day, space them out through the daylight hours to take advantage of your body’s natural rhythms. Here are some suggestions to avoid eating late at night:
- Try to eat a balanced dinner at least two hours before you go to bed, and take a walk afterwards when possible.
- Sip on soothing herbal tea or flavored water (without sugar).
- Be aware that watching TV (especially food-related ads) can trigger your desire to eat.
- Sometimes it can help to create new nighttime rituals that don’t involve eating, such as light stretching or yoga, taking a warm bath, listening to soothing music, or reading (or listening to) a book.
But if you find yourself up late at night—whether it’s due to a hard day at work, regular shiftwork, or temporary shifts due to jet lag or an infant’s night feedings—resist the urge to snack out of boredom or to “keep your energy up.” Shift workers should pack or purchase a healthy meal to eat during their work hours—one that includes lean protein and complex carbohydrates such as whole grains, fruits, and vegetables. Eat early in the shift if possible, so you’ll have the energy you need to think and move efficiently. Travelers and parents should look for healthy snacks that follow a similar pattern. And try to limit coffee, tea, and other sources of caffeine to just two to four servings a day.
Of course, eating is just one half of the CR equation. Getting enough sleep is important too, so read HPRC’s overview for great tips on how Warfighters can improve their sleep.
Holiday parties provide opportunities to relax and enjoy good food and good times with family, friends, and colleagues. But they also can derail your weight and fitness goals. Buffet tables laden with calorie-rich treats and beverages can weaken the resolve of even the most committed folks. To keep yourself on track, remember these tips:
- Never go to a party hungry. Eat a protein-rich food before you go. Protein foods tell your brain that you’re satisfied and help you avoid overindulging. Low-fat milk or yogurt or a handful of nuts are great choices.
- Follow the MyPlate strategies for filling your party plate: Fill half your plate with fruits and vegetables then fill the rest with whole grains and lean protein such as fish or chicken.
- Choose wine over fancy mixed drinks or beer, and be sure to drink in moderation: one drink for women and two drinks for men. Sip slowly to make your drink last through the evening.
- If it’s a potluck, you really are in luck. Offer to bring a healthy salad or entrée, and fill your plate with your own delicious creation.
- Don’t waste your calories (and taste buds) on desserts that you don’t absolutely love. Choose your favorite and then share it with a friend. You’ll eat slower while you and your friend chat, and cherish the moment as much as the sweet!
In a 1960s TV cartoon series, George Jetson of The Jetsons simply popped a pill when he wanted to eat. “Dinner in a pill” was promised as the food of the future. So why hasn’t technology delivered on its promise? Simply put, no dietary supplement can reproduce the aromas, flavors, textures, or nutritional value of oven-roasted turkey, crusty, fresh-baked bread, juicy ripe pineapple, fragrant hot tea, or any other wholesome, delicious, performance-enhancing real food or beverage. And substituting dietary supplements for real food won’t help performance either – check out our video here. So skip supplements—not meals. To learn more about how real foods should come before dietary supplements, check out HPRC’s article in Operation Supplement Safety (OPSS).
The phrase “Garbage in, garbage out” was coined first by computer experts back in the 1960s. Since then, the phrase has gained a wider usage—even to the world of performance nutrition. Providing your body with high-quality fuels and nutrients is crucial to optimizing your performance. Like the poorly fueled runner in HPRC’s video, you’re likely to find that a diet of high-fat or sugary foods and drinks (“garbage in”) produces less than optimal results (“garbage out”). Instead, choose wholesome foods such as lean meats and fish, fresh fruits and vegetables, whole grains, and low-fat dairy products, which provide high-quality fuels and nutrients.
Food and health are hot topics these days. Just turn on the TV, pick up a magazine, or glance at the margins of your social networking site and you’ll hear and read about the supposed health benefits of dietary supplements containing this or that food component and the promises that they will “burn belly fat” or some similar claim.
Many of these promising food components belong to a group of compounds referred to as phytochemicals—chemicals produced by plants as a means of protecting the plants from various diseases.
Interestingly, when you eat plants (such as fruits and vegetables), the phytochemicals they contain might protect you from disease too. Researchers have found that people who eat a lot of fruits and vegetables have lower rates of heart disease, cancer, diabetes, and many other diseases. Scientists haven’t discovered exactly how these compounds work to protect us, but they have discovered that they seem to have a synergistic effect. That is, the compounds seem to work better in combination, especially when they are supplied in their natural form—whole foods. Consuming isolated single compounds, as in dietary supplements, rarely has the same beneficial effect as eating the whole food. See these resources about fruits and vegetables and how they may impact your overall health.
Focusing on single nutrients (in pill form) is not only expensive, it just doesn’t offer the promise that a balanced, varied diet can. Focus on food, instead. For more information about the benefits of food versus dietary supplements, check out this OPSS brochure, “Nutrition: Fueled for Fitness.”
Nutrition experts at the Institute of Medicine—or IOM—of the National Academies of Sciences gather extensive information to make nutrition recommendations for the American public. One major result is known as the Dietary Reference Intakes, or (acronym number one) DRI. You might come across some of the DRI’s acronyms when reading how to fuel your body or considering a dietary supplement, so it’s helpful to know what they mean and where they came from.
The Estimated Average Requirements (acronym number two: EAR) are the average amount of nutrients that half of all healthy people need each day. EARs differ depending on life stage and gender. Remember, though, they’re simply an average. Scientists use statistics based on this average to calculate the Recommended Dietary Allowances (acronym number three: RDA).
The RDAs are the daily nutrient goals for essentially all healthy people, again based on life stage and gender. For example, the RDAs of some nutrients (such as vitamin C) for a 13-year-old boy are very different from those for a 25-year-old pregnant woman.
The Adequate Intakes (acronym number four: AI) are the—you guessed it—adequate daily amounts of nutrients that healthy people of a particular life stage or gender need. AIs are given when there isn’t enough scientific evidence for a stronger recommendation, that is, an RDA. For example, the IOM suggests an AI for one type of omega-3 fatty acids—alpha linoleic acid—of 1.6 grams per day for men and 1.1 grams per day for women because scientists just aren’t sure yet how much is optimal.
Tolerable Upper Intake Levels (fifth and final acronym, for now: UL) are the highest daily amounts of nutrients that you can consume without risk of toxicity. Many vitamins and minerals—even essential ones—can be toxic when consumed in excess. For example, because too much vitamin A can cause liver damage, a UL has been established for this essential nutrient.
So, if you remember nothing else, remember to get your RDAs and AIs every day, but don’t exceed the ULs!
The USDA Food and Nutrition Information Center provides links to the DRI Tables, but generally speaking you can meet all your daily nutrient intake goals (the RDAs and AIs) by following a healthy diet that includes lean proteins, whole grains, fruits, vegetables, and low-fat dairy products. And be aware that recommendations do change. IOM reviews the most current nutrition science and updates the tables when necessary to keep up with the latest knowledge, which means better health for Warfighters and their families.
The Human Performance Resource Center is here to serve Warfighters and their families, commanders, and healthcare providers. If you’ve visited before, you probably know that we focus on “total force fitness.” But do you really know what that means—or how HPRC got started? If you’re curious, check out this PDF that describes HPRC, what we do, and the vast amount of information we cover. In addition, you may have noticed that we use the term “human performance optimization” throughout our site; this article also explains what that means.
The Department of Defense (DoD) Safety Review Panel published their findings on DMAA in a recent report now available through HPRC. The Assistant Secretary of Defense for Health Affairs asked the Safety Review Panel to evaluate the safety of DMAA-containing dietary supplement products. The Panel has recommended that the sale of DMAA-containing products be prohibited in all military exchanges.
HPRC maintains a list of dietary supplement products containing DMAA and periodically updates this list. The most recent version can be found on HPRC’s website. Note that, as of the FDA announcement in April 2013, DMAA is illegal in the U.S. as an ingredient in dietary supplements. For more information, visit the OPSS FAQ about DMAA. Operation Supplement Safety (OPSS) can provide service members and their families with information to make informed decisions about dietary supplement use. For the full DoD Safety Review Panel report, see the link on HPRC's Dietary Supplements web page.
Grapefruit is a tropical fruit known for its lip-puckering flavor. It contains vitamin C and many other nutrients and is a regular feature at the breakfast table. Grapefruit and its extracts also show up as flavoring agents in beverages and are sometimes added to dietary supplements.
Despite its many health benefits, grapefruit can pose a risk for people taking certain drugs. That’s because grapefruit can affect the way drugs are broken down or transported in the body—potentially increasing or decreasing the drugs’ effectiveness.
If you enjoy eating grapefruit or grapefruit-containing products, be aware of potential interactions when taking medication. If you take prescription or over-the-counter drugs, ask your doctor or pharmacist if you should avoid grapefruit. This consumer update from the Food and Drug Administration has more information.
Sodium—a component of table salt—is an essential element. It helps your muscles and nerves function correctly and maintains the proper balance of your body’s fluids. However, too much sodium in your diet may increase your risk of high blood pressure, heart attack, stroke, and certain types of cancer.
The average American consumes about 3,400 milligrams (mg) of sodium every day, mostly in the form of salt. But the current Dietary Guidelines for Americans recommends that adults limit their sodium intake to just 2,300 milligrams per day—roughly the amount in one teaspoon of table salt.
The guidelines also recommend that certain “at-risk” groups limit their sodium intake to about 1,500 mg per day: adults over the age of 51, African Americans, and people who have high blood pressure, diabetes, or kidney disease.
Recently, the Institute of Medicine (IOM) looked at the evidence supporting the current recommendations regarding sodium intake. IOM concluded:
- Research supports current recommendations to reduce sodium intake to about 2,300 mg daily.
- More research is needed to support the recommendation that those “at risk” should cut back to 1,500 mg or less a day.
Bottom line? If you’re in an at-risk group, speak to your doctor or registered dietitian about whether you should reduce your salt intake. For just about everyone else: Cut back on the salt.
How? Most of the sodium Americans consume comes from processed foods—tomato sauce, soups, canned foods, bread, and prepared mixes—but it can also come from foods naturally high in sodium—cheese and some types of seafood. Also, many restaurant foods are high in sodium, but sometimes you can request low sodium items. The best way to ensure a low sodium diet is to eat whole foods such as fresh or frozen fruits and vegetables; lean, unprocessed poultry and fish; unsalted nuts; whole grains; and low-fat dairy products such as skim milk or yogurt. For more information, check out this CDC web page.
For additional information and other conclusions from the study, see the news release (which includes a link to the full study) from the National Academies.