The grapefruit diet was among one of the first fad diets to be introduced to the public.
Popularized as the “Hollywood diet,” the grapefruit diet involves eating grapefruit or drinking its juice with every meal.
Supporters of the diet claim grapefruit can help burn fat, quickly leading to weight loss in as few as 12 days. But there’s limited research to support these claims.
This article explores the research behind the grapefruit diet and whether a grapefruit diet is effective and safe for weight loss.
Unlike single food diets like the cabbage soup diet, the grapefruit diet consists of more than just grapefruit.
The diet calls for a protein-rich meal plan that incorporates a grapefruit or grapefruit juice at every meal.
The grapefruit diet promises quick and rapid weight loss due to claims that grapefruit has fat-burning enzymes.
Supporters of the diet believe you can lose as much as 10 pounds in 12 days.
Despite anecdotal evidence, there’s no research that supports claims of this fat-burning enzyme.
The grapefruit diet incorporates grapefruit into every meal and promises rapid weight loss due to fat-burning enzymes found in grapefruits. However, there’s no research to support this claim.
There are multiple versions of guidelines for the diet, but many sources claim it should last 2 or 3 weeks.
Every version is low in carbohydrates and calories and high in protein.
In some versions, the diet calls for consuming no more than 800 calories per day.
Generally, people following the grapefruit diet can prepare their foods however they like, including with spices, salad dressings, or butter.
Examples of meals include:
- Breakfast: two boiled eggs, two slices of bacon, and 1/2 grapefruit or 8 ounces of grapefruit juice
- Lunch: salad with dressing, any meat in any amount, and 1/2 grapefruit or 8 ounces of grapefruit juice
- Dinner: any kind of meat prepared any way, salad or red and green vegetables, coffee or tea, and 1/2 grapefruit or 8 ounces of grapefruit juice
- Bedtime snack: 8 ounces of skim milk
Multiple versions of the grapefruit diet exist, but every version is high in protein and low in carbohydrates and calories. Some versions limit you to just 800 calories per day.
Incorporating low calorie, highly nutritious foods like grapefruit into your diet is a smart and healthy choice — not just for weight loss, if that’s your goal, but for your overall health.
A single grapefruit contains over 60% of your recommended daily intake of vitamin C.
Vitamin C has antioxidant properties known to protect and strengthen your immune system (
In addition to protecting your immune system, research shows that grapefruit consumption is associated with higher intake of magnesium, potassium, dietary fiber, and improved diet quality (
Fiber and antioxidant-rich fruits like grapefruit may help protect against heart disease and stroke (
Grapefruit’s fiber-rich content may also help you feel fuller and eat fewer calories throughout the day (5), which may help with weight loss.
Although grapefruit has long been associated with weight loss (
Since no clearly established guidelines for the grapefruit diet exist, it’s impossible to evaluate the full benefits of this diet.
Grapefruits are low in calories and highly nutritious. That said, more research is needed to support claims that they can help with weight loss.
Although grapefruits are a low calorie, nutrient-dense option with many health benefits, this diet is problematic for other reasons.
There’s no evidence of magical fat-burning enzymes associated with grapefruits.
Quick, temporary weight loss associated with the grapefruit diet is likely due to the low calorie and low carb intake (
While low-calorie diets may result in initial weight loss, they’re rarely successful for those seeking long-term results.
There are health drawbacks, too.
Low calorie diets can weaken your bones, lower your metabolism, and cause fatigue, muscle loss, and nutrient deficiencies (
Another negative aspect of the diet plan is its limitations.
Twelve days on such a restricted plan may be possible, but eating the same foods and such few calories every day could lead some people to ultimately abandon the plan.
The grapefruit diet is also ambiguous. With multiple versions, it’s bound to cause confusion among followers.
In addition, most salad dressings and meats you can eat on the grapefruit diet — especially the daily morning bacon — are high in saturated fats and cholesterol.
Low calorie diets like the grapefruit diet may result in initial weight loss, but they have their share of health drawbacks. The restrictive diet is also unsustainable, limiting, and confusing.
Although claims of some magical fat-burning enzyme in grapefruits aren’t backed by research, studies have found grapefruit to be positively associated with weight loss.
One study found that participants who consumed grapefruit daily with meals experienced reduced waist size (
A 2014 study found that body weight, waist circumference, and body mass index (BMI) were lower among female grapefruit consumers when compared to non-consumers (
More current research is needed to determine the connection between grapefruit consumption and weight loss.
Although quick and temporary weight loss is possible on the grapefruit diet, it’s probably due to the fact that you’re consuming less than 1,000 calories a day (
Promises of losing 10 pounds in 12 days is unrealistic and unsustainable.
You may initially lose weight on this diet. But studies show that low calorie diets rarely keep weight off for good (
Studies have found grapefruit can help with weight loss, but weight loss on the grapefruit diet may be due to consuming fewer calories.
More current research is needed to determine the connection between grapefruit and weight loss.
Grapefruit juice and fresh grapefruit can be part of a balanced, healthy diet (
But grapefruit can also interfere with certain medications, including:
- some statin drugs that lower cholesterol, such as Zocor (simvastatin) and Lipitor (atorvastatin)
- some drugs that lower blood pressure, such as Procardia and Adalat CC (both nifedipine)
- some organ-transplant rejection drugs, such as Sandimmune and Neoral (both cyclosporine)
- some anti-anxiety drugs, such as buspirone
- some corticosteroids that treat Crohn’s disease or ulcerative colitis, such as Entocort EC and Uceris (both budesonide)
- some drugs that treat abnormal heart rhythms, such as Pacerone and Nexterone (both amiodarone)
- some antihistamines, such as Allegra (fexofenadine)
Grapefruit juice tends to interfere with the action of these drugs because it contains a class of chemicals called furanocoumarins.
Studies show that furanocoumarins may increase the blood levels of over 85 medications (18).
By slowing down how your body normally breaks down medications in your gut and liver, grapefruit can increase the side effects of these drugs, increasing your risk for complications.
For other drugs, such as antihistamines, grapefruit may have the opposite effect, reducing the drug’s effectiveness (
Ask your doctor or pharmacist if you can have fresh grapefruit or grapefruit juice while taking these and other medications.
Grapefruit can be part of a healthy diet, but it can also interfere with certain medications. Ask your doctor before consuming grapefruit when taking medication.
Outside of a couple of small studies, there’s no evidence to suggest there’s any magical power found in grapefruit other than the fact that it’s a low calorie, highly nutritious citrus fruit.
While this diet may help you drop pounds quickly, the weight will likely return as quickly as it left.
It’s a quick fix without any real potential of long-term sustainability.
Well-rounded diets incorporate a variety of healthy foods and fruits.
Instead of focusing just on grapefruits, aim for the recommended 2 to 2.5 cups of fruits per day (
Grapefruits can be part of these servings — but you don’t need to consume them at every meal.