The Best (and Worst) Diet Foods
Can frozen dinners, liquid meals, and sugar substitutes really help you shed pounds?
By Hallie Levine, Hallie Levine is a freelance writer in New York City who has written about health and fitness for more than 20 national publications, including Glamour, Newsweek, and the New York Post.
Walk into the local A&P and you're deluged with diet foods: low carb, low fat, low sugar, low calorie...all promising great taste, convenience, and the ability to quickly squeeze you back into your skinny jeans. Meal-replacement shakes will "help control hunger for up to 4 hours." Low-carb ice cream allows you to "savor the sweet without the sacrifice." Americans spent almost $63 billion on these products in 2005, an 18% increase from the $53 billion spent in 2002, reports market research group ACNielsen.
But despite our consumption of low everything, we're not slimming down. "Diet-food sales are growing, but so are our waistlines--rates of obesity in this country are increasing each year," says Dave Grotto, RD, a spokesperson for the American Dietetic Association, echoing the sentiment of most nutritionists. "Many of these foods can play a role in a healthy diet, but by themselves, they're not the magic bullet that can lead to permanent weight loss."
Before you throw up your hands in exasperation (and toss a bag of chips into your grocery cart), read Prevention's report. We delved into the latest research--including new studies calling into question the long-term effectiveness of popular diets--and interviewed leading weight loss specialists, nutritionists, and, yes, real dieters to zero in on the foods that really can help you lose. What follows: the science behind the products, who they're best for, and what not to waste your money on.
Frozen Fixes
Americans spent about $1.4 billion on low-cal frozen dinners (such as Lean Cuisine, Weight Watchers, and Healthy Choice) in 2004. These single-serving meals cost $3 to $5 each, pack up to 400 calories, and can be quickly microwaved for lunch or dinner.
The Science A 2004 University of Illinois study found that women who followed a 1,365-calorie diet in which they ate two packaged frozen entrées a day shed about 5 pounds more in 8 weeks than those who were instructed to follow a diet (with the same number of calories) based on the food pyramid.
Use Them If you find it hard to guesstimate portions. "Frozen meals give your eyes and stomach a chance to readjust to what servings should be--I often advise patients to eat them for a week or two, and then keep the little trays and use them while making dinner as an easy way to eyeball portions," says Madelyn Fernstrom, PhD, director of the Weight Management Center at the University of Pittsburgh Medical Center.
Frozen meals are also a sound option for busy dieters with no time (or desire) to cook and those who would otherwise grab fast food or order in pizza. "I've used them over the years whenever I've needed to lose weight because you can't beat the convenience: You just pop them into a microwave. And there's no way you can overeat," says Michelle Tennant, 36, a publicist in Asheville, NC. "I try to pick the ones that have whole wheat or are mostly meat and vegetables, as I find they stick with me longer and I don't have a blood sugar crash."
Lose Them If you're a foodie. "If you savor your meals, enjoy cooking, and really notice the different tastes, textures, and smells of food, these products won't offer enough stimulation for you," says Wahida Karmally, DrPH, RD, director of nutrition at the Irving Center for Clinical Research at Columbia University. The skimpy servings also may not provide enough calories if you're fairly active. "I used to take Lean Cuisine entrées to work and eat them for lunch because they're so convenient, but the portions were way too small to satisfy my appetite," says Sylvia Sklar, 60, a professor at McGill University in Montreal.
"I was starving an hour later." One reason: Some of these dinners have less than 20 g of protein per serving--not enough to keep many women, especially active ones, satisfied, says Kathy McManus, RD, director of the department of nutrition at Brigham and Women's Hospital in Boston. If that describes you, look for a product with at least 20 g of protein, such as Kraft's line of South Beach Diet frozen entrées and Lean Cuisine's new Dinnertime Selects. One final caveat: Avoid this category if you have high blood pressure. Many entrées have 800 mg of sodium or more, about one-third of the federal government's recommended upper limit for a day's intake.
Bottom Line They can give dieters a push. "Frozen entrées may make dieting easier because they remove the guesswork when it comes to figuring out portion sizes," explains Donald Hensrud, MD, an obesity specialist at the Mayo Clinic in Rochester, MN. Just make sure to supplement your meal with hefty sides of fruits and veggies to ensure you get enough nutrients and stay full. "The fruit and vegetable portion in most of these meals is tiny. You need 7 to 10 servings of fruits and vegetables a day," says Karen Collins, RD, nutrition advisor to the American Institute for Cancer Research.
Liquid Lunch
Meal-replacement shakes, generally around 250 calories a serving, sub for one or two meals a day; you eat a snack and a third meal of about 700 calories on your own. Sales dropped 16% from 2002 to 2004, but this method is still popular with some dieters.
The Science A 2003 Columbia University meta-analysis of six studies found that people who used a liquid meal replacement were likely to lose more weight (on average, 7 pounds) in a year than those who simply followed a reduced-calorie diet of about 1,200 calories per day. (No word on how the dieters fared after that.)
Use Them If you're always on the go--liquid meal replacements are quick, easy, and convenient. "Our program often recommends the shakes to executives who travel a lot--they can take them along instead of eating at an airport or ordering in room service," says Hensrud. "We sometimes even suggest they have one before a business dinner, so they eat a light meal of, say, a salad, instead of a high-fat, high-calorie entrée."
Because the shakes are fairly low in calories, you'll want to add fruit or a side dish of vegetables to provide more filling fiber. "I tell patients to mix the shakes in a blender with ice and fruit, which makes them thicker and also whips up air to fill their stomach," says Scott Isaacs, MD, an endocrinologist at Emory University. These drinks can also be helpful for night eaters: "If one of your diet danger times is after dark, you can always use a shake to curb nighttime cravings for sweets," says McManus.
Lose Them If you're an emotional eater. "The minute you get upset, you'll find a shake just won't cut it," says Christine Gerbstadt, MD, RD, a spokesperson for the American Dietetic Association. "I had one client who lost 100 pounds on a liquid diet plan but eventually gained it all back--during times of stress she just couldn't get over the urge to have food in her mouth." Liquid diets can also be hard to stick to for more than a few weeks. "I found it impossible to stay on," says Sara Dombroff, a 31-year-old lawyer in New York City. "I had to have shakes for breakfast and lunch, so I'd spend the whole day dreaming of real food."
That may be because most people enjoy the satisfaction of chewing, says Ann Kulze, MD, a physician in Charleston, SC, and author of Dr. Ann's 10-Step Diet. "In my experience, people who use diet shakes tend to complain of more hunger and less satisfaction than dieters who are on solid food. Besides, eating the same thing day in and day out is boring, and that makes it much more likely that you'll weaken and binge on doughnuts."
Bottom Line They can be a quick and easy diet aid for the time-pressed. But experts warn that dieting on liquid meal replacements may not lead to lasting weight loss because they don't teach you how to eat "real" food. "I spent 5 years supervising a liquid-meal-replacement center, and I can tell you that while people in the program did a great job of losing weight, they did an even better job of gaining it back once they stopped because they never learned healthy eating habits," says Grotto. If you use shakes as grab-and-go meals or snacks, look for a product that has 220 to 300 calories and 12 to 15 g of protein to fill you up. Some users report that more protein than that gives the shake a grainy, unpleasant taste.
Low-Carb Lowdown
About 6 years ago, low-carbohydrate bars, shakes, cereals, and ice cream flooded the market, with sales peaking in 2004 at an estimated $2.6 billion, according to ACNielsen. But this trend has cooled: Sales of low-carb products fell by 10% in 2005, and Atkins Nutritionals Inc. filed for bankruptcy in July of that year. Today, "We're seeing more and more of these products repositioned as 'low sugar' or 'low glycemic,' with companies claiming that they're digested more slowly and thus are less likely to affect blood sugar," says Tom Vierhile, an analyst for market research group Datamonitor, Inc.
The Science There is some evidence that low-carb diets--though not specific products--promote weight loss. But it's not the lack of carbs that's key: "It's the fact that people on low-carb diets tend to eat more protein, which is very satisfying and filling," explains Jonathan Waitman, MD, a clinical nutrition specialist in the Comprehensive Weight Control Program at Weill Cornell Medical Center in New York City.
A recent University of Washington study found that people on a diet that was 30% protein ate fewer calories and reported less hunger than those who followed a meal plan that was 15% protein (the diets had identical amounts of carbs, which suggests that protein really made the difference).
Use Them For an occasional snack or breakfast, especially if you tend to wake up ravenous or get hungry between meals. "I was always starving in the mornings until I switched from a regular shake to a high-protein one, which had about four times as much protein and kept me full until lunch," says dieter Dombroff, who didn't mind the latter's thick texture. New York City nutritionist Joy Bauer, RD, author of The 90/10 Weight Loss Plan, seconds the approach: "I often recommend low-carbohydrate bread to clients because some brands use oat or soy flour. That bumps up fiber and protein and thus really helps to control blood sugar, so they'll be less hungry later."
Lose Them If you're not willing to cut portion size: They're often as high in fat and calories as the foods they're designed to replace. "I routinely have to explain to patients that these products are calorie traps; manufacturers are just replacing sugar with fat," says Kulze. Then there's the taste issue. "The cereals have the texture of cardboard, the ice cream has a slimy feel in your mouth, and the pancake mix isn't anything like the real thing," says Hilary Bruel, a 32-year-old graphic designer in Needham, MA.
"The only product I liked was the Atkins Endulge Peanut Butter Cups, but with 320 calories and 26 g of fat in a handful, they slowed down my weight loss." And that's not the only price you pay. "Some low-carb sweets replace regular sugar with large amounts of sugar alcohols like maltitol, which can have a laxative effect," says Hensrud.
Bottom Line Staples such as bread and cereal make sense, but skip the snacks. "It's a lot cheaper--and healthier--to have a snack like a banana with peanut butter for about the same amount of calories," says Gerbstadt.
The Fat-Free Facts
Reduced-fat products have been around since the '80s and are still ultrapopular weight loss foods. Sales topped $35 billion in 2005, dwarfing the performance of all other categories, such as low carb, says ACNielsen.
The Science Research suggests that a low-fat diet may not do the trick when it comes to weight loss. A recent Harvard Medical School study found that those on a low-fat (20% of calories) diet actually gained 6 pounds, while those on a moderate-fat (35%) diet lost 9 over 18 months.
Use Them If you're a big eater who needs voluminous portions to feel satisfied. "Because some of the fat-free salad dressings, for example, are lower in calories, you can put a little on a huge amount of vegetables and eat a lot for very few calories," explains Bauer. "The same holds true for fat-free cheese--I encourage clients to go for a sharp Cheddar, which still has a strong taste."
Dairy products such as milk and cheese are high in saturated fat, so 1% or fat-free versions are also a great way to get needed calcium and protein. The catch to this category: Some fat-free salad dressings have added sugar, so check the label (2 tablespoons of fat-free Italian, for example, contain 15 calories, while 2 tablespoons of a honey Dijon have 50).
Lose Them If you're diabetic, prediabetic, or carry a lot of weight around your middle. All of these indicate that you may be prone to insulin resistance, and low-fat foods, which are likely to be loaded with sugar, could worsen the problem. "Most fat-free foods, with the exception of dairy products, tend to be refined carbohydrates, which will just drive up your blood sugars and overwork your pancreas, making you even more insulin resistant," says McManus. You should also steer clear of them if you have elevated triglyceride levels.
"I've seen patients who think they are being superhealthy following a fat-free diet. They're shocked to learn they have insulin resistance or even high triglycerides--but as soon as they cut back on the refined carbohydrates and add in some healthy fat, the problem goes away," says Isaacs.
Bottom Line Low fat usually doesn't equal low calorie, so go with a small portion of a regular version instead. "Most of these products have just as many--if not more--calories than the full-fat versions. The companies have simply cut out fat and poured in the sugar," says Fernstrom.
One of the most common mistakes she sees is too much faith in low-fat peanut butter. "People assume that because it's reduced fat, they can eat another tablespoon. But they're getting almost as many calories as with the regular variety, and it's actually more harmful to their health because they're losing 3 g of heart-healthy fat and instead adding in extra carbohydrates and sugar."
Sweet--Or Not?
The sugar-free business is booming: Sales are up 24% since 1999, with sugarless gum and soda the two top sellers, according to data tracker Mintel. Americans spent an estimated $8.8 billion on low-sugar products last year, reports ACNielsen, and many of these were sweetened with additives such as sucralose (Splenda), aspartame (NutraSweet and Equal), or saccharin (Sweet'n Low).
The Science Preliminary research isn't so sweet. It suggests that these products may actually ramp up your appetite, especially if consumed as a beverage. A 2004 Purdue University study found that rats that drank liquids artificially sweetened with saccharin ate more food than those that had been fed sugar-sweetened liquids. Humans who chug sodas with these sweeteners may react by overeating, too: Your risk of being overweight rises 65% for every diet soda you down each day, according to a study presented in June 2005 at the American Diabetes Association meeting.
Use Them If you're a diabetic who can't use sugar or honey. "Low-calorie sweeteners don't affect blood sugar, so they allow diabetics to get some sweetness into their diet without endangering their health," says Fernstrom. And if you like cakes and cookies, Splenda--the additive that's best at retaining its sweetness at high temperatures--makes it possible to create low-cal desserts. "I use a mix of sugar and Splenda when I bake--I don't notice a difference at all," says Leigh-Anne Kent, 37, a financial analyst in Denver.
Lose Them If you have a sweet tooth. "(Dieters) turn to artificial sweeteners as a way to stem their sugar cravings, but they just make things worse," says Kulze. "They drink a Diet Coke and minutes later they're craving cookies. Once they cut out sugar substitutes, those yearnings drop."
Bottom Line Unless you are diabetic, you're better off dumping sugar rather than a sugar substitute into your coffee. Why? Artificial sweeteners may make you feel extra hungry and fool your body into thinking sweet foods have fewer calories, so you unconsciously munch on more of them, says Sharon Fowler, MPH, a faculty associate in the division of clinical epidemiology at the University of Texas Health Science Center at San Antonio. So go ahead, have the real thing. Just have a little--and enjoy it a lot.
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