Another year has passed and we still don't fully understand what happens when we eat—why we gain or lose weight, which foods should be embraced or cast aside, how nutrients are absorbed. But that just makes researchers even hungrier to find out. This past year, scientists explored everything from the effect of diet on heart health to the link between particular foods and fatness. From their work, U.S. News has selected the following eight as the standouts in the diet news of 2011.
1. Food pyramid knocked down. In June, the U.S. Department of Agriculture replaced the decades-old food pyramid with a dinner plate divided into sectors like a pie chart. The plate is touted as a more straightforward way to dish out healthy eating advice than the pyramid, a rainbow-striped triangle with a staircase edge. Introduced in 1992 and updated in 2005, the pyramid had long been felt by nutritionists to be too difficult to interpret. The dinner plate features four sections—one piled with fruits, one with veggies, one with grains, one with protein, and a small side cup of dairy. The symbol is designed to convey, as simply as possible, key eating recommendations from the 2010 Dietary Guidelines, like filling half your plate with fruits and veggies.
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2. Weight Watchers lauded. The popular points-counting program is more effective than standard weight-loss guidance, according to a study published in September in the Lancet. Researchers tracked 772 overweight and moderately obese people who either followed Weight Watchers or got weight-loss guidance from their primary care doctors. After a year, those in the Weight Watchers group had dropped 15 pounds compared with 7 pounds for the doctor-advised group. What's more, 61 percent of the Weight Watchers dieters stuck with the program for the full 12 months the study lasted, compared with 54 percent for the standard-care group. The program's success is likely explained by its regular weigh-ins and group meetings, which hold dieters accountable while offering support and motivation. The study was funded by Weight Watchers, but an independent research team was responsible for all data collection and analysis. Another study, published in November in the British Medical Journal, found that people lost more weight—and saved money—when they enrolled in a commercial weight-loss program as opposed to a primary care-based program. After 12 weeks, Weight Watchers participants had lost 9.8 pounds; those on a primary care-guided plan had dropped 3 pounds.
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3. Extra chips take the blame. Small diet tweaks can make a big difference, according to a study published in June in the New England Journal of Medicine. Harvard researchers tracked nearly 121,000 people in their 30s, 40s, and 50s for 20 years, assessing their weight, diet, and lifestyle habits every four years. They found that various foods and drinks had a larger-than-expected influence over whether people got fatter (or slimmer) over time. Potato chips were the worst offenders, leading to more weight gain per serving than any other food examined. People who ate an extra serving per day (about 12 chips) gained 1.7 pounds more over four years than those who didn't indulge in extra chips. And knocking back just one additional sugar-sweetened beverage a day added an extra pound over four years. Other fattening choices included red and processed meats, as well as alcohol. On the flip side, the foods most associated with weight loss were yogurt, whole grains, fruit, veggies, and nuts. People who added a daily serving of yogurt to their diet, for example, shed nearly 1 pound every four years. The findings suggest that, regardless of calories, some foods trigger weight gain because of their chemistry or how our bodies process them, the researchers said.
4. Healthy-eating guidelines overhauled. Government health officials released the 2010 Dietary Guidelines for Americans in January, the latest in a series of five-year updates. The 95-page report's bottom line: The overwhelming majority of Americans eat too much, and too much of what they eat isn't good for them. Salt, saturated and trans fats, and refined carbohydrates are the main culprits, the report explained. Translation: Keep sweets, fatty meats like ground beef and steak, and white bread and white rice off the table; instead build a menu around fruits, vegetables, whole grains, low-fat dairy, lean protein, and fish and seafood. That style of eating staves off hunger pangs between meals while cutting calories, and provides recommended amounts of "nutrients of concern"—potassium, fiber, calcium, and vitamin D—that often get short shrift in the typical American diet.
[For Realistic Advice on Healthy Eating, Federal Dietary Guidelines Fall Short]
5. There's a "marriage diet." Husbands and wives often begin eating like each other, suggests a study published in September in the American Journal of Public Health. After analyzing the eating behavior of more than 3,000 people, researchers observed that spouses, more than friends or siblings, had the greatest effect on each other's eating habits, for better or for worse. That's likely because of the strength of the shared environment; most husbands and wives regularly prepare food for each other. Another study, presented at the annual meeting of the American Sociological Association in August, found that marriage and divorce influence the sexes differently. While married men and women tend to gain more weight than their single counterparts, women generally pack on more pounds than their husbands. Two years after divorcing, separated partners were heavier than couples who remained married, but men recorded larger weight gains than women.
6. Salt questioned, bad fats flagged on heart health. Two studies published by the Cochrane Collaboration, a nonprofit research organization, shed light on the link between diet and heart health. In one, researchers took a hard look at salt. They analyzed seven studies with a total of roughly 6,500 participants and concluded that reducing salt intake might not delay death or prevent cardiovascular disease, as some research has suggested. Still, the researchers said, this "does not mean that asking people to reduce salt should be stopped." Shunning salt has been shown repeatedly to reduce blood pressure. The jury's still out.
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Another Cochrane analysis focused on types of fat. After reviewing 48 studies, researchers reported that replacing saturated fats (like butter) with unsaturated fats (monounsaturated fats like olive oil and polyunsaturated fats like canola and peanut oil) may reduce risk of heart disease—but they couldn't say whether the mono- or polyunsaturated varieties were best. Regardless, disease protection appeared to be strongest when the switch was made for at least two years, the researchers said. Surprisingly, they found no clear heart benefit to reducing total fat consumption.
7. "Freshman 15" debunked. Where did the idea come from that first-year college students are likely to add 15 pounds or so? It's more like an average of 2.4 pounds for women and 3.4 pounds for men, according to a study in the December issue of Social Science Quarterly. The findings are based on data from a survey that tracked 7,418 young people. For students who picked up more weight than average, heavy drinking and juggling a job and school were most often to blame.
[Fighting the Freshman 15 With Calorie Counts]
8. Hormones try to defeat weight loss. Certain hormones may make it difficult for some dieters to keep the weight off, according to an October study by an Australian research team in the New England Journal of Medicine. In 35 overweight or obese patients who lost at least 10 percent of their body weight after following an ultralow-calorie diet for 10 weeks and then got diet counseling for the next 52 weeks, the level of several key hormones at 62 weeks rose or fell in ways that seemed to encourage regaining the lost weight. Ghrelin, which stimulates the appetite, went up as participants slimmed down. Their feelings of hunger were also tracked; the participants were hungrier at the 62-week point than they were when the study started.
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