The Grapefruit Diet is a short-term diet plan that requires you to consume grapefruit or grapefruit juice with each meal. Proponents of the diet claim that grapefruit contains calorie-burning enzymes that can lead to quick weight loss. But is there any science to back up this idea, or is this a diet that only results in short-term weight loss due to a reduction in calories?
To find out more information, we looked at the science behind the grapefruit diet. Our research team investigated the facts and took a look at studies linked to this eating plan. Here’s what we discovered.
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What Is The Grapefruit Diet?
Losing weight and dieting is nothing new to humankind. They’ve been documented as early as 1820 when famous poet Lord Byron popularized the vinegar and water diet to drop a few pounds. And, according to Business Insider, the most popular diet today is the DASH diet (Dietary Approaches to Stop Hypertension).
Today, we’re digging into the Grapefruit Diet, asking what it is, how it works, if it’s safe, and how it measures up.
The Grapefruit Diet’s other names include “the Hollywood Diet,” “the 10-Days-on-10-lbs-off Diet”, “the Egg and Grapefruit diet,” and, for a short time, “The Mayo Diet” (not authorized by the Mayo Clinic, by the way). This crash diet (losing a substantial amount of weight over a short period) seems to have no specific launching point but first appeared on the radar in the 1930s with the claims of losing ten pounds in two weeks.
In the most basic sense, the grapefruit diet is a calorie-restricting diet plan that includes eating half a grapefruit (or four ounces of unsweetened grapefruit juice) with each meal. It boasts the claim that adding grapefruit to this restricted diet is the key to burning unwanted fat, particularly due to enzymes that act as a fat-burning accelerant.
So what are those enzymes and how do they work? Before we dig into the enzyme claim, let’s take a closer look at the diet itself.
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What To Eat On The Grapefruit Diet
This calorie-restrictive diet allows the dieter to consume 800-1000 calories per day with little to no carbohydrates for a period of ten days to two weeks. The original blueprint outlined a breakfast of two eggs and two pieces of bacon, a green salad for lunch, and dinner of meat or fish and fresh vegetables with an additional glass of skim milk for an evening snack. Also, 1/2 fresh grapefruit or eight ounces of non-sweetened grapefruit juice before each meal.
Modern updates to this diet include the addition of more protein, specifically at lunch. It restricts starchy vegetables such as most root vegetables and legumes, as well as sugars, and although some variations of the Grapefruit Diet now allow high-carbohydrate foods such as bread and pasta in very small portions, the diet in its purest form restricts all high-carbohydrate foods.
The instructions are very simple.
Eat a half a grapefruit or drink 4 oz. of 100% (unsweetened) grapefruit juice before each meal.
Breakfast: Two eggs and two slices of bacon.
Lunch: Protein of your choice with salad and dressing.
Dinner: Meat or fish with vegetables.
Bedtime snack: Eight ounces of skim milk or tomato juice.
Some versions of this diet limit carbs and increase high-fat, high-cholesterol, or cut an incredible amount of calories. You can eat whatever, as long as you include grapefruit for every meal.
Combining bacon and salad for this diet has a fat-burning effect.
Classic Version of the Grapefruit Diet
No sugars or carbs (including pizza, potatoes, rice, bread)
No certain types of food like white onions and celery.
Protein-heavy food like meat and eggs.
Grapefruit or grapefruit juice during or before each meal.
Eight glasses of water and a cup of coffee per day.
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The Grapefruit Diet & Dietary Restrictions
Vegetarians and vegans: the original diet includes meat, so it would need tweaking before vegetarians and vegans can go on it.
Gluten-free: The diet cuts back on carbs but doesn’t completely remove gluten. People who are sensitive to it should check food labels to avoid gluten.
What Does The Grapefruit Diet Do?
When you follow it precisely, The Grapefruit Diet claims to promote a loss of almost a pound a day, and as much as to 10-15 pounds in two weeks, which is quite significant.
This diet does not include or require:
Packaged foods and meals
What’s The Cost Of The Grapefruit Diet?
The Grapefruit Diet isn’t a particularly costly endeavor, using mostly staple ingredients of meats and vegetables. Besides the purchase of these staples, the only extra cost would be the addition of the grapefruit.
At about 90 cents per pound, and the average grapefruit weighing in at about half a pound, the weekly cost of grapefruits would run just over five dollars. Considering that this diet omits high-carbohydrate foods/snacks from the grocery list, one might even argue that it could save you money during the two-week period.
How Does The Grapefruit Diet Nutrition Stack Up?
Since grapefruit is the star of this diet, let’s start with it.
Grapefruits (blond, pink and ruby) are a hybrid of the blood orange and the pomelo. They are low in calories with only 41 calories per 1/2 fruit.
A grapefruit half provides 59% of the daily allowance of vitamin C and 25% of vitamin A – vitamin antioxidants that help to boost the immune system, according to Nutrition Journal.
Pink and red grapefruits are also high in the phytonutrients limonoids and lycopene, both of which help in fighting free radicals, according to Food & Nutrition Research. No doubt pink and ruby red grapefruits are a low-calorie super-fruit.
How Does The Grapefruit Diet Work?
As we said, this diet is a calorie-restrictive eating plan. The average caloric intake for healthy adults ranges from 1600-3200 calories a day depending on weight, gender, and lifestyle.
The Grapefruit Diet restricts caloric consumption to 800-1000 calories per day, mostly from proteins and fats as well as green and red vegetables. With that said, we can’t find reliable information as far as the ratio of protein to fat to carbohydrate consumption. However, by looking at the daily menu, it’s easy to discern that protein tops the list with fat coming in second and carbohydrates lagging.
To promote weight loss, the Grapefruit Diet takes a three-prong approach:
Consume grapefruit or unsweetened grapefruit juice before each meal.
There is no doubt that caloric restriction will lead to a loss of body weight. This time-proven method has been shown with dieting over the centuries.
Next comes the carbohydrate restriction. This macronutrient is the source of fuel most readily available for our body. Carbohydrates break down into blood sugars and are also stored as glycogen in the muscles for quick bursts of muscle fuel.
So why does carbohydrate restriction lead to loss of fat? When you remove carbohydrates from your diet, you force your body to search for alternative fuel.
Though the process of breaking down fat into a consumable fuel isn’t quite as efficient as just grabbing blood sugars when the body is out of options it uses fat as the next line of fuel.
Understanding fuel consumption by the body helps us to understand the premise behind carbohydrate restrictive diets:
Restrict readily available fuel.
Forces the body to turn to fat for fuel.
Stores of fat are consumed by the body.
This type of diet, according to Frontiers in Psychology, is called ketogenic dieting. By understanding the dietary restrictions as above, we can see that The Grapefruit Diet falls into the category of ketogenic dieting, or carbohydrates restrictive dieting, putting the body into the state of ketosis.
The Grapefruit Diet And Ketosis
Ketosis is the state of the body when the primary source of fuel (glucose, glycogen) is unavailable, and the body begins to churn fat into fuel.
As we say above, however, the Grapefruit Diet also includes consumption of grapefruit to take fat-burning to a higher level. It’s all about the enzymes. So let’s talk enzymes.
Enzymes and Digestion
Digestion is a fascinating process, done almost entirely by the work of enzymes that aid in accelerating chemical reactions to break down macronutrients into absorbable micronutrients. We employ an entire battalion of enzymes in our mouth, stomach, and intestines for digestion.
Three biggies–amylase, lipase, and trypsin—are in charge of carbs, fats, and proteins. Think about a saltine cracker and the way it seems to melt when you combine it with the saliva in your mouth. That’s amylase breaking down the starches. So, what sort of enzyme does grapefruit contain, then, that might aid in the ‘burning’ of fat?
Where Does Grapefruit Fit In?
Because fat-burning allegedly comes from the grapefruit enzymes, it only makes sense to investigate this stimulus. However, the most prominent enzyme found in grapefruit, CYP3A4, is a drug-metabolizing enzyme.
Although hearing an enzyme helps metabolism may confuse some into believing it will encourage quick weight loss, in reality, this enzyme works in the liver and intestines, metabolizing drugs to incite and aid in the absorption process. That can be good and bad, as some medications may absorb too readily, and some at a slower rate than you need.
Therefore, some blood pressure- or cholesterol-lowering medications, antihistamines, organ transplant rejection, anti-anxiety drugs, and corticosteroids recommend that you don’t consume grapefruit and grapefruit juice while taking them, says the FDA. While this enzyme does aid in metabolizing drugs, unfortunately, burning fat isn’t in the job description.
Specifically, grapefruit could interact with the following:
statin drugs (for lowering cholesterol) like atorvastatin (Lipitor), simvastatin (Zocor), and pravastatin (Pravachol)
nifedipine, medication for blood pressure
antihistamines like Allegra
certain anti-anxiety medication like buspirone (BuSpar)
amiodarone, anti-arrhythmia medication
Benefits Of The Grapefruit Diet
The most notable benefit of The Grapefruit Diet is the rapid loss of weight. Also, grapefruit is a tasty superfood filled with antioxidants, phytonutrients, and vitamins. Plus, grapefruit is a good source of fiber and is water-dense. Eating a grapefruit half before a meal will aid in satiety and help to control the appetite. Because regulating appetite is a key factor for successful weight loss, eating a grapefruit half isn’t a bad idea.
As long as there are no drug contraindications, this fruit is a safe and effective way to bump up nutrition and aid in appetite control. Besides that, grapefruit can help boost your immune system, according to BMC Complementary & Alternative Medicine.
The Grapefruit Diet Alternatives
As far as crash diets go, there certainly isn’t a shortage of methods available. Although the list is seemingly endless, below are a few crash diets that encourage the rapid reduction of weight:
Juice Fast: This is a basic liquid diet consisting of a fast of juiced fruits and veggies.
Cabbage Soup Diet: As the name implies, mostly cabbage soup makes up this diet.
3-Day Diet: The diet itself isn’t as clear as the caloric restrictions of 800 calories a day.
The Master Cleanse: “the Lemonade Diet,” this diet is only a lemonade-type drink, salt water, and a laxative tea.
Xtreme Fat Loss Diet: This five-day diet starts with a cheat (high-calorie, high-carb) day, then four days of intense dieting, including meal replacement shakes and fasting, a moderate carb day, as well as a protein-only day.
Although not for dietary recommendations, the above list shows diets similar to the Grapefruit Diet. These crash diets were put together for quick weight reduction. When adhering to these diets, you can expect results similar to The Grapefruit Diet.
It is a common fact that a significant factor of good health is to consume plenty of water. It’s also no secret that most weight loss diets will encourage adherence to plenty of water consumption.
Although eight glasses of water per day are the recommendation for healthy adults, adding to that number can aid in appetite suppression as well as releasing stores of excessive water in the cells, thereby leading to more weight loss, according to The American Journal of Clinical Nutrition.
Adequate water consumption will also aid in bowel regularity and relieve belly bloat from a backed-up colon.
Grapefruit Diet & Exercise
Although the Grapefruit Diet doesn’t come with exercise recommendations, input or fuel is only half of the battle against the bulge. Regular exercise promotes good physical and emotional health.
When discussing diets, however, it’s important to note that increasing muscle mass can be a key component to weight loss. Because muscle burns more energy than fat, the leaner the body, the higher the metabolism, and therefore the greater the calories that the body burns.
Also, sustained aerobic activity, such as bicycling, swimming, running, and walking will increase caloric burn as well as utilize fat as the source of energy when staying within a fat-burning heart rate zone, according to Nature Clinical Practice Endocrinology & Metabolism.
With that in mind, although not explicitly discussed within the parameters of The Grapefruit Diet, adding exercise into the mix will increase success with any diet.
Contraindications With The Grapefruit Diet
While considering any diet, it’s important to keep in mind the risks of dieting. Studies have shown that crash-dieting over time can slow your metabolism making it harder to keep off the weight. Not only that, but yo-yo dieting (losing weight and gaining it back over and over again) has negative consequences for your heart.
Furthermore, on the Grapefruit Diet, the need to specifically familiarize yourself with any prescription and over-the-counter drugs you are taking is imperative. Understanding how these medications interact with the metabolizing enzyme in grapefruit will help to keep you safe from the dangers of too much or too little drug for your condition. Lastly, because of the reduction in calories and nutrition, in general, it’s not uncommon to feel fatigue or even suffer from headaches.
Grapefruit Diet Pros & Cons
Evidence of results in a short amount of time.
Not only good for weight loss but also for general dietary health.
No evidence supporting claims about a fat-burning enzyme.
Weight loss could be temporary because of how quickly people lose pounds.
Grapefruit can interfere with some medications.
Quite limited regarding food choices.
What Users Are Saying
“Taking with several other supplements, and notice an immediate reduction on my hypertension and blood pressure.”
“I had a horrible allergic reaction (rash all over my body, puffy hands, and puffed out eyes) that lasted for 2 weeks.”
“Not a detectable difference with or without it.”
The Bottom Line On The Grapefruit Diet
The final word on the Grapefruit Diet is that in its most basic form, it is a calorie-restrictive ketogenic diet. Limiting calories to almost a third of the daily allowance is a severe hit to the system. Will you lose weight? No doubt. Will you lose fat? Also, yes. If quick weight loss is the ultimate goal, the Grapefruit Diet will deliver. But, there’s a good chance you’ll lose muscle, the diet is difficult to follow because of strict food limitations, and hunger will be a big problem.
If you’d like to drop more pounds, then we suggest you select a diet program that is backed by solid science, does not call for extreme calorie restrictions and is supported by plenty of encouraging user reviews.
Among the best weight-loss programs we’ve seen this year is one called Noom. Personalized meal plans, interactive support groups, health and food tracking, and individual coaching are just a few of the amazing things Noom offers. You don’t have to cut back to 800 calories a day, and results are lasting.
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The grapefruit diet has been around since the 1930s. The theory is that enzymes in grapefruit burn fat, spurring up to 10 pounds of weight loss in 10-12 days.
What is the grapefruit diet plan?
The essentials: protein and grapefruit (or juice) at each meal, with few white carbs. Stricter versions may only allow 800-1000 calories.
What are the ingredients in Grapefruit Diet?
While the main focus in the Grapefruit Diet is grapefruit it is not the only food consumed. While on the Grapefruit Diet you are instructed to eat a half of a plain grapefruit. If you prefer you may instead drink 1 cup of unsweetened grapefruit juice. You consume the fruit or the fruit juice before each meal. This is suppose to increase weight loss. No other fruits are allowed except for grapefruit. The diet also restricts starches and eliminates sugar.
What are the side effects of Grapefruit Diet?
It is not common to have any side effects while on the Grapefruit Diet, but they include dry feeling in the mouth, dryness of the nose, headache, and nervousness.
Does Grapefruit Diet work?
Many users have had success on the Grapefruit Diet meal plan. The diet is low in carbohydrates and restricted to 800 calories per day or less. It is recommended to consult a doctor before you start the diet because the amount of calories you are allowed to eat are so slow and also the lack of variety of food groups. It is also not recommended as a long term plan. There is no scientific proof that weight loss is associated with eating grapefruits because cutting calories alone would lead to weight loss.
What is the price of Grapefruit Diet?
A 33 ounce bottle of grapefruit juice is around $3.50. The cost of your meal would vary.
Where can I buy Grapefruit Diet?
Grapefruits and grapefruit juice are available everywhere juice is sold. This includes grocery stores, mass merchants, and wholesale clubs.
How should I take Grapefruit Diet?
The Grapefruit Diet should be used for 21 days.
How do I contact Grapefruit Diet customer service?
There is no customer service for the Grapefruit Diet.
Can I return Grapefruit Diet?
Most retailers have return policies for fruits based on their own policies.
What are the most common complaints about Grapefruit Diet?
The diet is boring and too routine. There is not much variety in what you can eat. It is difficult to stick to the plan. The grapefruit diet, while high in protein, eliminates other foods which could lead to health problems.