The Grapefruit Diet

By Kathleen M. Zelman, MPH, RD, LD
WebMD Expert Review

Reviewed by Brunilda Nazario, MD

The Grapefruit Diet: What It Is

The Grapefruit Diet, has been around a long time -- since at least the 1930s. A short-term, quick weight loss plan also known as the Hollywood Diet or the Mayo Diet (not associated with the Mayo Clinic), the Grapefruit Diet surprisingly has survived the test of time, being circulated by word of mouth, online and in book form -- yet no one claims ownership of the plan.

The premise of the Grapefruit Diet is based on an alleged "magical" ingredient in grapefruits, that, when eaten with protein, theoretically triggers fat burning and causes weight loss. The diet is designed to promote fast weight loss; unfortunately, the weight lost is primarily from fluids and not fat and generally returns as soon as the dieter goes off the diet.

The seeds of the Atkins Diet may have been sown by the food choices of the wacky, very low calorie, low carbohydrate, high protein Grapefruit Diet.

Most versions promise a 10-pound weight loss during the 12-day diet. Dieters who want more than 12 days of monotony must wait two days before starting the diet again. Exercise is recommended in some versions and absent in others. Long-term weight control is not part of the diet plan.

The Grapefruit Diet: What You Can Eat

In most versions of the Grapefruit Diet, a small variety of foods are required at breakfast, lunch, dinner, and at bedtime. Dieters are encouraged to drink black coffee and plenty of water throughout the day.

Sample Meal Plan:

* Breakfast

2 eggs, 2 slices of bacon, black coffee, 1/2 grapefruit or 8 ounces grapefruit juice

* Lunch

Salad with salad dressing, unlimited meat, and 1/2 grapefruit or 8 ounces grapefruit juice

* Dinner

Red or green vegetables (except starchy ones such as peas, beans, corn, sweet potatoes) or salad, unlimited meat or fish, and 1/2 grapefruit or 8 ounces grapefruit juice

* Bedtime snack

8 ounces skim milk

In the Grapefruit Diet you can use all the butter and salad dressing you desire and prepare foods in any method, including fried. Grapefruit juice must be unsweetened. Any food or beverage not on the diet is not allowed. Snacking is only permitted after dinner. Drink 64 ounces of water daily. Eat all of the approved foods.

The Grapefruit Diet: How It Works

This low-carbohydrate, moderate-protein diet is another low-calorie diet averaging 800-1,000 calories in most versions. Most people will lose weight -- with or without grapefruit on the Grapefruit Diet -- when calories are dramatically reduced to this level. Unfortunately, there are no explanations for how the mysterious grapefruit enzyme works and why it is only contained in grapefruit and not other citrus fruits.

No scientific studies to date substantiate grapefruit's power to burn fat.

One small study published in 2006 and funded by the Florida Department of Citrus found that the addition of a half grapefruit or 4 ounces of juice with meals resulted in an average weight loss of more than 3 pounds in 12 weeks, with some participants losing 10 pounds. Researchers suspect the addition of grapefruit to the otherwise healthy meals reduced insulin levels and promoted a small weight loss. Study participants also "slightly enhanced" their physical activity, which could also explain the weight loss.

While grapefruit is a very nutritious low-calorie fruit (66-84 calories per serving), loaded with vitamin C and fiber, it is not a mysterious fat burner. The low glycemic index, high fiber, and low calorie nature of the fruit may reduce insulin levels and help dieters feel full and eat fewer calories. Beyond that, no magic appears to be at work with the Grapefruit Diet. Experts say one small study is not enough to pin magical powers on this fruit.

The Grapefruit Diet: What the Experts Say

"There is no evidence that grapefruit has fat-burning enzymes nor is it a magic bullet for weight loss" says American Dietetic Association past president Connie Diekman.

Kelly Brownell, PhD, director of the Rudd Center for Food Policy and Obesity at Yale University, agrees. "There is no scientific basis to the claim that grapefruit is special in this way," he writes in a WebMD commentary. "Grapefruit is a good food, but so are other healthy foods like vegetables and other fruits."

Beyond the nutritious grapefruit, experts agree, the Grapefruit Diet has numerous pitfalls and should not be used for anyone looking for sustainable, long-term weight control. The limited variety of foods is so restrictive it does little to help dieters improve their eating habits or behaviors.

And such a limited variety of foods in small portions is a prescription for boredom, monotony, and taste fatigue. It's exactly the formula that causes most dieters to throw in the towel, disgusted with trying to lose weight.

"On again, off again diets perpetuate the misunderstanding of healthy weight loss," says Washington University Nutrition Director, Diekman. "Sure, you will lose weight, but it will be primarily fluids and not the fat associated with health risks. And most people regain it as fast as they lost it -- so why bother?" she says.

Healthy weight loss is a process not a promise. "If you want long-term success, don't waste your time on the Grapefruit Diet," Diekman says. "Look for a flexible weight loss diet individualized to your needs, [one] that addresses behaviors, includes a wide variety of healthy foods, exercise, and can be enjoyed."


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The Grapefruit Diet: Food for Thought

The expert consensus seems to be pretty clear: Don't bother with the Grapefruit Diet.

While nutritious grapefruit certainly can be part of a healthy weight loss plan, it contains no mysterious fat-burning properties. If you love grapefruit, reap the benefits of this supernutritious food by enjoying a serving before meals. The addition of a half grapefruit or a glass of grapefruit juice before meals may help fill you up so you'll eat fewer calories at meals, potentially losing weight. For added nutrition, choose pink grapefruit, which is rich in beta-carotene.

Along with a well-balanced, sensible, calorie-controlled diet, don't forget to include a regular dose of physical activity -- a scientifically proven way to burn fat and lose weight.

A claim the Grapefruit Diet just can't make.

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Connie Diekman, MEd, RD, LD, FADA, president-elect, American Dietetic Association; director of university nutrition, Washington University, St Louis; Kelly D. Brownell, PhD, professor of psychology, Yale University, director, the Yale Center for Eating and Weight Disorders. Fujioka, K. Journal of Medicinal Food, Spring 2006; vol 9(1): pp 49-54.

Reviewed on January 12, 2010

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