For Rob Nager, the epiphany occurred at Abercrombie & Fitch. He was picking through a stack of cargo pants and asked a clerk if they were available in a 42-inch waist. "Dude," the kid sneered, "we don't make pants that big."

 

Nager, 38, faced a choice. He could ask the little weasel to step outside, or he could do something about his 250-pound frame. He opted for peace and a new waistline.

 

He tried Weight Watchers, then Atkins. Both plans helped him slim down, but the flab always returned. Finally, Nager tried a weight-loss strategy that's been around since TVs were black-and-white; a strategy so old-school that one of the studies showing that it works went on for a decade. His throwback approach: meal-replacement beverages (MRs, in the weight-loss world). Nager just said no to solid food. Instead, he quaffed shakes in place of meals, eventually losing 22 pounds. That was 2 years ago. The weight is still off.

 

They're simple and they're foolproof. That's why MRs work for men who are too busy to worry about calories, says Allan Geliebter, Ph.D., a research psychologist at the New York Obesity Research Center at St. Luke's-Roosevelt Hospital in Manhattan. "They just know that this is what they consume, and they don't have to think too much about it," says Geliebter. The best candidate for liquid lunches (and breakfasts), he says, is a guy who's healthy but wants to drop 10 to 20 pounds.

 

MRs come in two basic forms: liquid-only programs administered by physicians, and the more familiar, over-the-counter products sold in groceries and drugstores. The doctor-prescribed ones (like Optifast and HMR) replace all meals and are usually for seriously overweight patients. We'll focus on the over-the-counter options, like Slim-Fast, Met-Rx, and Atkins Nutritionals. They contain about 200 calories per serving, plus a dose of vitamins and minerals, and they're typically used to replace one or two meals a day. Most are available in ready-to-drink cans or in powder packets that can be mixed with water or milk.

Last year, Steven Heymsfield, M.D., also of St. Luke's-Roosevelt Hospital, analyzed a half-dozen small studies comparing Slim-Fast with conventional low-calorie diets. He found that people who guzzle the shakes in place of one or two meals a day consistently lose 7 percent to 8 percent of their body weight after 1 year. That's about 15 pounds for a 200-pound man, which, he notes, is roughly the same reduction you might achieve by taking a weight-loss drug such as Xenical--minus the risk of a drug's side effects (which include such horrors as "oily stools"). Meanwhile, Dr. Heymsfield showed that people who simply try to eat less food maintain a weight loss closer to 3 percent.

 

Pretty impressive, but most of the studies Dr. Heymsfield analyzed lasted only a year. Any obesity doctor worth his fat calipers knows that anyone can lose a few pounds, but keeping that weight off over the long term is far more difficult.

 

So how about a 10-year study? That's right. Last fall, George Blackburn, M.D., an expert in nutrition and metabolism at Harvard medical school, released findings from a study comparing two groups of people in the aptly named town of Pound, Wisconsin. The Harvard team gave one group Slim-Fast, with instructions to replace two meals a day with the shakes in an effort to shed pounds. When they reached their goal weights, the Slim-Fast folks were encouraged to keep pounds off by replacing one meal per day with a shake. The comparison group simply "followed the eating habits of their community," says Dr. Blackburn--which, in Wisconsin, was likely to include lots of cheese and bratwurst.

 

A decade later, the men using Slim-Fast had maintained a 7-pound weight loss, on average. Big deal, right? Well, yes, when you consider that their cheesehead counterparts gained 25 pounds, on average, during that same 10-year stretch.

How long does this kind of diet last? As long as you want it to. Some patients stay on only until the weight comes off. Others, like Nager, stay on, to some degree, for life. "Data imply that one meal replacement per day can be used long-term," says Fabricatore, who recommends regular consultation with a licensed nutritionist if you plan on using two MRs per day for more than 5 months.

 

Nager says he doesn't miss the three-square-meals-a-day life; in fact, he says he's happy not to constantly be worried about food anymore. "If I stop my routine, I'm going to get hungry," he says. "Then I'd start slipping back into my old habits. This is a deal I'm willing to make." His weight loss has had a domino effect. Not only has he become a fitness fanatic, but Nager quit his high-pressure job in corporate sales and started a dog-walking business. "I feel better; I look better," he says.