The Honest Truth About The Grapefruit Diet

May 21, 2017 — by Matt Theis0



The Honest Truth About The Grapefruit Diet

May 21, 2017 — by Matt Theis0

The Grapefruit Diet is a popular weight-loss meal plan, but does it actually work? In this article, we answer that very question and a whole lot more...

We’ve seen fad diets come and go, but one that seems to be sticking around is the Grapefruit Diet.  Is that because there’s actually something to it?  Is it really worth it?

In this article, we’ll answer those questions and more.  We’ll answer questions like:

  • What is the grapefruit diet?
  • Does it work?
  • How much weight-loss will occur?

And a whole lot more.  So let’s just dive right in, shall we?

What Is The Grapefruit Diet?

What Is The Grapefruit Diet

While there are many variations of weight-loss diets that involve grapefruit, the classic grapefruit diet follows these rules:

  • short duration (12 days)
  • high protein
  • low-calories (1000/day)
  • grapefruit with every meal

There are a few other nuances but that’s basically the grapefruit diet at it’s core.  Put simply, the grapefruit diet involves eating very few calories (like 1000/day), high protein, and grapefruit before every meal.

here’s an example of the classic Grapefruit diet.



½ Grapefruit (30 calories)

2 Eggs (160 calories)

2 Strips Of Bacon (100 calories)


½ Grapefruit (30 calories)

Salad (100 calories)

Meat (200 calories)


½ Grapefruit (30 calories)

Salad or steamed vegetables (100 calories)

Meat/Fish (200 calories)

Total Calories: 950

Total Protein: 100g (400 Calories from Protein)

Although the idea that grapefruit may be beneficial for maintaining a lean body composition allegedly dates back to the 1930s, what we know as “the grapefruit diet” saw a massive rise in popularity in 2006.


A study out of the Department of Nutrition and Metabolic Research at the Scripps Clinic in La Jolla, California found that grapefruit consumption was associated with weight-loss in subjects with Metabolic Syndrome.

91 patients who were considered obese consumed either:

  1. placebo capsules with apple juice
  2. grapefruit capsules with apple juice
  3. placebo capsules with grapefruit juice
  4. placebo capsule with half a fresh grapefruit

3 times a day, before each meal.

Subjects who ate the half a fresh grapefruit before each meal lost 3.5 lbs (1.6kg) in 12 weeks.  Subjects who drank grapefruit juice before each meal lost 3.3 lbs (1.5kg) and subjects who took grapefruit capsules before each meal lost 2.4 lbs (1.1kg).  The placebo group lost a little over half a pound (.3kg).

Some subjects also showed signs of improved Insulin Resistance.  The researchers in this study concluded that grapefruit consumption was associated with weight-loss but how it worked was unknown.

Now, these results sure are encouraging, but without tracking things like calorie intake and exercise habits, it’s far from conclusive.

Further Research

A later 2012 study conducted at the University Of Arizona observed less encouraging results.  Subjects consuming grapefruit 3 times a day before each meal lost only a small amount of weight compared to those who didn’t.

However, some improvements in blood pressure and lipid profile were observed.

A 2011 study conducted at the Vanderbilt University School of Medicine found that pre-loading each meal with grapefruit or grapefruit juice was no more effective than pre-loading with water.  This study did find that pre-loading meals was an effective weight-loss strategy.  It’s just that Grapefruit wasn’t special in this regard.

It was, however, associated with an improved lipid profile, similar to the 2012 study we talked about above.

So, while that first study was certainly encouraging, if you look at all the research on the grapefruit diet as a whole, it’s pretty clear that grapefruit doesn’t have much to do with it.

How Does The Grapefruit Diet Supposedly Work?

How Does The Grapefruit Diet Work?

The Grapefruit diet is premised on the idea that Grapefruit contains certain Flavonoids with direct fat-burning properties.  While it is true that some of the molecules found in Grapefruits may have anti-obesity effects, there’s no evidence that these molecules can result i the type of rapid weight-loss that the Grapefruit diet promises.

Among the components of Grapefruit thought to help facilitate fat-loss are:

  • Naringin
  • Naringenin
  • Hesperidin

Unfortunately, most of the research pertaining to how these substances influence body weight or fat-loss are in mice.

There are some promising studies involving people which use these molecules in combination with other fat-loss stimulating substances like Synephrine and Caffeine.

One study showed that Hesperidin and Caffeine reduces fat mass in obese subjects.  Another study shown that a combination of Naringin, Hesperidin, and Synephrine substantially increased the Metabolic Rate more than Synephrine alone.

Naringenin may also increase glucose uptake in muscle cells, a potentially beneficial action as far as weight-loss is concerned.

However, on their own, these compounds are far from the miracle weight-loss solutions they’re often made out to be.  They may have some anti-obesity properties, but there’s no way they account for the drastic weight-loss that the Grapefruit diet is known for.

How Does It Actually Work?

So, if Grapefruits don’t have magical weight-loss powers, then how does the grapefruit diet work?  Well, it’s actually really simple…

Most versions of the diet require a substantially reduced calorie intake.  In many cases, you’re cutting your diet from a normal (2000+ calorie) diet to something like 1000 calories/day.

It’s simply a matter of calories in vs calories out.

If you take in around 2000 calories a day and burn around 2000 calories a day, your body weight will remain the same.  If you suddenly cut your calorie intake to half of that, or 1000 calories a day, but keep burning the same amount, you’ll lose weight.

This is simple physics, not some magic diet plan.

In fact, given that you need to burn about 3500 calories to lose a pound of fat, cutting your calories by 1000/day would result in you losing a pound of fat every 3 days or so.

This is why grapefruit diet works.  You’re essentially starving yourself for a short period of time.  It has nothing to do with eating Grapefruit.  Nothing at all…

What Kind Of Results Can I Expect From The Grapefruit Diet?

Grapefruit Diet Results

Different variations of the Grapefruit Diet promise different results, you can usually expect to lose around 3-5 pounds in 12 days.  Again, this is simply because of the massive amount of calories you’re cutting.  It has nothing to do with how many grapefruits you eat.

Some variations of the diet claim you’ll lose 10 pounds in 12 days, but in order for you to do this you would need to cut your calories by 2500/day.  This isn’t healthy OR reasonable for most people.  Cutting your calories drastically is usually not recommended for maintaining long-term

It’s far healthier (and much easier) to cut your calories by something like 20% for a few weeks, as opposed to 50% for 12 days.  Such a massive drop will leave you hungry, irritable, and much weaker.  Not to mention you’re almost SURE to start losing a significant amount of muscle mass in such as deficit.

Grapefruit Nutrition

Grapefruits may not have inherent fat-burning powers, but they’re definitely a decent source of several important Vitamins and Minerals.  The chart below breaks is down…

Grapefruit Nutrition

The weight-loss benefits of eating Grapefruit are mostly due to the fact that it’s low in calories but contains a good amount of water.  Studies have shown that drinking water before meals can increase satiety (fullness) from food and result in lower calorie intake.

Supplements That Help

The truth is most fat-burners and weight-loss supplements don’t actually work.  Manufacturers of these types of products are usually just taking advantage of the fact that most people want to be leaner.  So they combine a bunch of hyped up Dr. Oz-recommended ingredients in one pill and call it a miracle weight-loss supplement.

To be clear, there is no “magic weight-loss pill” that will make you drop 10 pounds of fat in two weeks and keep it off.  However, there are some supplements which can shift the balance in your favor and help you get rid of unwanted fat.


Caffeine is used in just about every fat-burning supplement for one reason…It works!

Caffeine triggers the release of a group of chemicals called Catecholamines.  Included in this group are Dopamine and Noradrenaline which are responsible for the Central Nervous System activation that Caffeine causes.

However, these chemicals have another important job as well.  They directly stimulate Lipolysis, the breakdown of stored fat.  By increasing the amount of these chemicals floating around your blood stream, Caffeine can increase the amount of fat you burn from exercise.


Synephrine is similar to the once extremely popular fat-burner, Ephedrine, which is now banned in the US.  Both Ephedrine and Synephrine are beta-receptor agonists which essentially means they tell your body to breakdown more fat to be burned as energy.

While Synephrine certainly shares a mechanism of action with Ephedrine, the two molecules are actually pretty different.  Research shows that, while Ephedrine can be dangerous for some people, Synephrine is remarkably well-tolerated.

Research shows that Synephrine can increase fat-oxidation during exercise and increase the Resting Metabolic Rate as well.  Interestingly, Naringin and Hesperidin, two naturally occurring molecules in Grapefruit, have been shown to enhance the Metabolic Rate increase seen with Synephrine.


Rauwolscine basically functions as the inverse of Synephrine.  Instead of acting as a beta-receptor agonist, it acts as an alpha-receptor antagonist.  This essentially means it keeps the body in fat-loss mode longer and more intensely than would otherwise be possible.

Rauwolscine significantly increases the amount of fat your body can burn during exercise.  Combined with either Caffeine or Synephrine (or both), it becomes even more effective.

The Bottom Line

There’s nothing magical about Grapefruit.  Eating Grapefruit with every meal won’t make you suddenly lose a bunch of weight.  The class Gapefruit diet works because it forces you to consume substantially less calories.

If you cut the amount of calories you consume daily by half, you’ll lose weight pretty fast.  However, this isn’t necessarily a smart thing to do.  If you want to lose weight pretty quickly, dial back your calories by around 20% and use supplements that actually work.

Matt Theis

I'm Matt, Founder of Momentum Nutrition and SuppWithThat.com. I've spent the better part of the last decade researching and experimenting in the areas of fitness, nutrition, and supplementation, and this is where I write it all down.