What Should I Eat?
by Bonnie Liebman, October 2009
What does a healthy diet look like? Despite (or maybe because of) all the diet books, food pyramids, and expert advice, most people are still confused.
Yet we know which diets can lower the risk of heart disease, the major cause of death in the United States. Odds are, those same foods can also promote weight loss and help prevent diabetes and cancer.
The tricky part is summing up an entire diet in simple, easy-to-remember advice. Here's our try.
START WITH HEART
Want a diet that's likely to lower your heart disease risk over the next 10 years by 20 to 30 percent?
The OmniHeart Trial tested three variations of a vegetable-and-fruit-rich diet in people who had pre-hypertension or hypertension—that is, anyone with blood pressure above 120 over 80.1
Not in that group? Odds are you will be. Middle-aged Americans have a 90 percent chance of developing high blood pressure at some point in their lives.
The diets were remarkably effective. After six weeks, they had:
- Lowered systolic blood pressure by 13 to 16 points in people with hypertension (systolic blood pressure —the higher number—over 140). Blood pressure fell by 8 points in people who had pre-hypertension (systolic pressure between 120 and 139). "The diets lower blood pressure more than most drugs," says Frank Sacks, a cardiologist at the Harvard School of Public Health and one of OmniHeart's principal investigators.
- Lowered LDL ("bad") cholesterol by 20 to 24 points in people with high cholesterol. LDL fell by 5 points in people whose levels weren't high when the study started (they had LDL below 130). That's not quite what you'd get from a prescription statin drug like Lipitor (a drop of 50 to 100 points), but it's no small potatoes.
- Lowered damaging triglycerides by 9 to 16 points. Two of the thre potent? It wasn't just the low levels of saturated and trans fat (7 percent of calories), sodium (2,300 milligrams a day), and added sugar (2 to 5 teaspoons a day). It was also the high levels of potassium(4,700 mg a day), magnesium (500 mg), calcium (1,200 mg), and fiber (30 grams) in the diets. Which of those nutrients mattered? "The study wasn't designed to say," says Sacks.
AND THE WINNER IS…
Each of OmniHeart's three diets was higher in one of the following:
- carbs (mostly from foods containing a total of 5 teaspoons of sugar a day),
- protein (more than half from beans, nuts, seeds, tofu, and other non-animal sources), or
- unsaturated fat (mostly from canola and olive oil).
The results: a tie between the diets higher in protein and unsaturated fat. "We think that the health benefits of the protein and unsaturated fat diets are about the same, and that both are a little better than the carb diet," says Sacks. "Although the protein diet lowered triglycerides better than the unsaturated fat diet, it also lowered HDL." That's a minus—HDL is the "good" cholesterol.
Further analyses showed that the protein diet was especially good at lowering Apo B (a key component of LDL cholesterol) and Apo C-III (a key component of triglycerides).2
"In a couple of years we may be giving much more weight to data on Apo B and especially Apo C-III," says Sacks. "Also, research on how to interpret changes in HDL is in a state of rapid development."
The bottom line: it's just too early to choose among the two diets. "At this point, I would award an approximate tie," says Sacks. "The idea is to encourage flexibility in using unsaturated fat and protein to replace carbs."
That's what's behind the diet we've come up with. It's a mix of the two best OmniHeart diets (protein and unsaturated fat), with a "wild card"—for those who can't resist—to eat more carbs.
Here's how it works:
- Start with unsaturated fat. We began with the OmniHeart's (Mediterranean-style) unsaturated-fat diet, which contains 4 tablespoons of oil per day. We kept 2 of them for salad dressing and for oil to sauté vegetables.
- Add protein. We traded the third tablespoon of oil for an extra serving of protein from beans (½ cup) or nuts (¼ cup), to get some of the benefits of the higher-protein diet.
- Add a wild card. We left the fourth tablespoon of oil as a wild card. You could use it to:
— sauté vegetables or dress salad,
— swap for an extra 2 or 3 oz. of poultry,
— swap for an extra serving of grain, or
— swap for sugar (in your cereal, sweetened yogurt, or a small cookie).
Each tablespoon of oil has 120 calories, so you can't use your wild card on a fudge brownie sundae or a burrito.
WATCH YOUR WEIGHT
Got a spare tire that you'd like to lose?
The OmniHeart diets weren't designed to melt pounds, even though many of the participants were overweight or obese.
"In fact, we made sure they didn't cut calories or we wouldn't have known how much each diet mattered," says Janis Swain, an OmniHeart dietitian at Brigham and Women's Hospital in Boston.
In a separate study, Sacks put 800 overweight adults on diets that were high or low in fat, carbs, or protein. After two years, weight loss was about the same.3 "So there is also a tie for weight loss," he notes.
However, we've tweaked the diet to make it easier for people to lose—or not gain—weight by cutting caloric beverages and eating foods that are less calorie dense.
But those are details. Here's the big picture of what to eat.
RULES OF THE ROAD
1. Make vegetables a main course. Vegetables or fruit are going to fill up at least half of your plate at lunch and dinner. It's easy to polish off 3 or 4 pieces of fruit as snacks or with breakfast or lunch. But when you're shooting for 6 to 8 servings of vegetables a day, it makes sense to make them part of a main dish like stir-fried vegetables, vegetable curry, vegetable fajitas, or a main-dish salad—all of which can have chunks of chicken, fish, lean meat, or tofu mixed in. It's not just that you need to boost the vegetables, but that by eating more of them, you're eating less of other foods. Used to having chicken or meat as your main dish for dinner? No problem. Just make sure that it's the size of a deck of cards, and surround it with enough side dish vegetables or salad to reach your total.
2. Keep saturated fat and cholesterol low. That means just a small (¼ lb.) portion of lean meat or poultry per day for a 2,000-calorie diet. (It's okay to have a more generous serving of fish.) Vegetarians can substitute veggie meats, tofu, or beans. Use eggs and non-low-fat cheeses sparingly. (Egg whites are okay.)
3. Don't overdo grains. Even whole grains are limited to four servings a day
if you're shooting for 2,000 calories. And a serving is a thin (1 oz.) slice of bread, not a typical (4 oz.) bagel. Eat a small bowl of cereal for breakfast and a sandwich at lunch and you're left with just a half cup of cereal, rice, or pasta for dinner. A half cup isn't much—it's the volume of two golf balls.
4. Minimize added sugar. A 2,000-calorie diet allows two teaspoons (8 grams) of added sugar a day. There's no room for more empty calories. That's about what you'd get in many breakfast cereals, two small cookies, or ¼ cup of ice cream. If you can't live without more sweets, swap your "wild card" for 120 calories' worth of dessert.
5. Keep a lid on sodium. In the OmniHeart study, sodium was limited to 2,300 milligrams a day. That means avoiding high-sodium processed foods.
6. Eat beans and nuts. "Of the three OmniHeart diets, the protein diet was the most challenging because it required so much bulk for the vegetable protein sources," says Sacks. In other words, people felt more full when they ate a diet rich in beans and nuts.4 That meant they might have shed some weight if the study had allowed them to cut calories. If beans seem dull, think Middle Eastern (hummus), Indian (curried lentils), French (cassoulet), Southwestern (black bean soup), or American (vegetarian chili). Or just throw some chickpeas into your salad. Nuts and seeds are easy to eat—too easy. If you can't stop at ¼ cup, use them as a garnish on salad or cereal or veggies. Otherwise, the calories can add up quickly.
7. Eat real food, not junk. Notice what's missing (or minimal) in this diet? It's not just sweets (cookies, cakes, ice cream, muffins, soda, etc.). It's also big bowls of pasta, big bagels, and big muffins. Most pizzas, panini sandwiches, wraps, and burritos are too big. Also gone are granola or energy bars, pita chips, and other junk disguised as health foods. Think of them as an occasional splurge.
8. Cut calorie density to lose weight. "People eat for weight or volume," explains Barbara Rolls of Pennsylvania State University. Her studies show that if you trim the calorie density—that is, the calories per bite—people leave the table feeling full but with fewer calories in their belly (and, eventually, with less belly). Her research team analyzed data from the Premier diet, which was similar to the OmniHeart higher-carb diet.5 "People who lowered their calorie density ended up eating fewer calories and losing more weight," she explains. "The change in calorie density was the biggest predictor of six-month weight loss. And those people ate a pound more food a day." Rolls got similar results in a one-year trial.6 "Both groups were told to eat smaller portions and less fat," she notes, "but only one group was also told to eat more fruits, vegetables, and broth-based soups." That group lost more weight. "We tell people to manage portions of calorie-dense foods and eat as much as they want of fruits and vegetables," Rolls explains. "They're free foods." Her advice doesn't apply to dried fruit or fruit juice. Nor does it apply to French fries, potato chips, or other starchy vegetables. "Non-starchy vegetables like celery are the best way to lower calorie density," says Rolls. "You're mostly eating water and some bulk. Fruit should also be unlimited because it's got a low calorie density. You can only eat so much because you're going to fill up."
9. Eat veggies instead. Adding vegetables only curbs calories if you eat less of everything else. Barbara Rolls tried either adding vegetables to a dinner or substituting them for other foods. "On the plate we had a prepared beef dish, a rice dish, and broccoli," she explains. "When we went from a quarter to half a plate of broccoli and made the meat and grain portions smaller, people ate fewer calories in the meal." The calories per bite—or calorie density—went down as the veggies went up. "But if we just added broccoli to the meat and grain, people didn't eat fewer calories," she adds. "So if your goal is to cut calorie intake, you have to substitute vegetables for other ingredients."
10. Cut liquid calories. When the Premier study began, most participants got 350 calories—nearly a fifth of their calories for the day—from soda, alcoholic beverages, juice, milk, and other drinks. (And in the OmniHeart study, participants were allowed up to 2 serv- ings of alcohol a day.) Trimming those calories mattered more than cutting calories from solid foods.7 "Only a reduction in liquid calorie intake was shown to significantly affect weight loss during the six-month follow-up," says Benjamin Caballero of the Johns Hopkins Bloomberg School of Public Health in Baltimore. To boost your odds of losing (or not gaining) weight, it makes sense to cut most liquid calories. That's why our diet substitutes fruit for fruit juice.
1 JAMA 294: 2455, 2005.
2 Am. J. Clin. Nutr. 87: 1623, 2008.
3 N. Engl. J. Med. 360: 859, 2009.
4 Am. J. Epidemiol. 169: 893, 2009.
5 Am. J. Clin. Nutr. 85: 1212, 2007.
6Am. J. Clin. Nutr. 85: 1465, 2007.
7 Am. J. Clin. Nutr. 89: 1299, 2009.