Is the Grapefruit Diet Fact or Fad?

Joyful female with two half of grapefruit instead eyes

The idea of a grapefruit diet has been around for a long time.

In fact, this diet has ties all the way back to the 1930s. It’s also known as the Hollywood diet because it has been so strongly associated with celebrities.

At face value, this diet can sound like a great way to lose weight.

But, does the grapefruit diet work or is it just another fad diet?

What is the Grapefruit Diet?

As you might imagine, grapefruit is the key component of this diet, but it isn’t the only component.

Basically, this diet is a very low calorie and low carb diet, where people are consuming half of a grapefruit (or some grapefruit juice) with every meal.

Basic grapefruit diet meal plan

For example, the image on the right is a meal plan from one website promoting the diet.

The diet is fairly simple because you are essentially following the same meal plan for up to 12 days.

After that, you are supposed to take a break for a few days. Then you can start it again if you want to.

There are two main concepts with this diet.

The first is the nutritional side of things.

So, the diet has you consuming a low amount of calories and carbs, while also consuming a relatively high amount of protein and fiber (relatively is the key word here, you might be consuming a decent amount of protein compared to the calories, but you’re still not consuming all that much protein).

From the weight loss perspective, this approach makes senses. If you cut down the amount of calories that you are taking in then yes, you will lose weight.

The other side of this diet is the grapefruit.

The grapefruit diet plays on the idea that there is something about grapefruit that is simply amazing for weight loss. In fact, the diet is probably why many of us inherently believe that concept.

But, does it stand up to scrutiny?

The Nutrition of Grapefruit

As fruits go, grapefruit is pretty interesting.

Most fruits are high in sugar (and by extension, carbs). But, if you’ve ever tried grapefruit, you’ll know that this isn’t the case. Grapefruits are actually very low in sugar and they have a low glycemic index and glycemic load because of this (1,2).

Halved grapefrult

Like most fruit, grapefruit also contains fiber. In particular, half an average grapefruit has 2 g of fiber.

Fiber is important for health, but grapefruit is hardly unique as a source of fiber.

Grapefruit does also have some interesting nutritional components, including vitamin A, vitamin C and a range of flavanols.

Finally, grapefruits tend to be pretty low in calories. For example, half of an average grapefruit is 52 calories (3).

At the same time, eating a grapefruit takes a bit of time, so it’s easy to see how people might feel satisfied (at least briefly) with this as part of a meal.

Grapefruit and Weight Loss

There really isn’t much about grapefruit that screams weight loss.

I think it’s appealing because you get the benefits of fruit while also consuming much less sugar than you would with another type of fruit.

There is also this idea that there is an enzyme in grapefruit that helps to burn fat.

Interestingly, there has even been some research that supports the potential of grapefruit itself to help with weight loss.

One experimental study looked at this, using the following four conditions:

  • Placebo capsules with apple juice
  • Grapefruit capsules with apple juice
  • Grapefruit juice with placebo capsules
  • Half of a fresh grapefruit with placebo capsules

The authors found that the groups that had grapefruit in some form (including the capsules) lost more weight than the placebo group.

At the same time, the group consuming the fresh grapefruit lost the most weight, although the differences between the groups were not significant (4).

The outcomes of that study looked like this:

Outcomes of research on grapefruit

It’s also worth noting that the study took place across 12 weeks.

As such, the change in weight loss wasn’t especially dramatic.

Beyond this, there have been very few studies that specifically focus on grapefruit and weight loss.

Overall, this means that we don’t completely know what impact grapefruit does have on weight loss. But, the outcomes of this study do suggest that there is some impact.

Variations on the Diet

Some sites do also promote an alternative version of the diet, one that does make a little more sense nutritionally. For example, here is a set of rules for one more modern approach (which comes from AppforHealth):

App for Health's Grapefruit diet

This approach to the diet is a lot more sensible.

To be honest, though, it’s not really a grapefruit diet at all and the only place that grapefruit even shows up is in breakfast.

More than anything, this alternative is simply a healthy eating plan that plays on the hype surrounding the grapefruit diet.

It’s also not especially helpful because many people looking at this plan wouldn’t actually know what a balanced lunch or dinner is anyway.

Does the Grapefruit Diet Work?

Essentially, the grapefruit diet is a fad diet, which means that the answer to ‘does the grapefruit diet work’ is yes… and no.

This diet is specifically designed to promote fast weight loss and the diet does do this to a degree.

After all, the diet is exceptionally low in calories. That alone will make you lose weight – any very low-calorie diet will.

The outcomes of research do suggest that grapefruit itself may also help with the weight loss. But, it’s hard to know how much of a difference the grapefruit makes practically.

The problem with this diet is that it’s extreme.

With most versions of the diet, you are consuming the same food every day for 12 days.

Additionally, you’re really not eating much for those 12 days.

Puzzled girl in a red shirt

Honestly, that sounds like torture.

This pattern is extremely common in fad diets, largely because it does result in weight loss.

I mean, you’re barely eating any food, of course you’re going to lose weight.

However, a lot of that weight loss is going to be water, especially for people doing the diet for the first time.

Additionally, you’re not doing your body any favors.

Starving yourself to lose weight affects many processes in the body, including processes that you need.

For example, having an extremely low level of calories also restricts your ability to build muscles.

This will often mean that people lose muscle mass at the same time as they lose weight.

That’s not a good thing. Plus, decreased muscle mass could make it harder to lose weight later, as your muscle mass does play a role in your metabolism (5).

Sustaining the Diet

The biggest issue with fad diets is that they can’t be sustained.

They might be a tool to lose weight fast, but they won’t work in the long-term.

After all, they don’t teach any healthy eating strategies.

In the case of the grapefruit diet, you’re only supposed to follow it for 12 days at a time.

Even if you can follow it for those 12 days without issue, you have to have a new approach once those days are over.

Most people won’t have that.

Realistically, if you did have a healthy eating strategy, you probably wouldn’t be following a fad diet to start off with.

Additionally, coming off the diet and onto a healthy eating approach can be hard.

Under the grapefruit diet, you are heavily restricted in the calories that you take in.

When people come off this type of diet, there is a strong temptation to overeat.

In many cases, people can actually put back on all the weight they lost. Some people even put on more than they lost.

This is called yo-yo dieting and it’s extremely unproductive and certainly isn’t good for your confidence or self-esteem.

At the end of the day, you might be able to lose weight in the short-term with this diet, but losing it in the long-term is very unlikely.

Losing Weight with Grapefruit

As I discussed earlier, there is some evidence that grapefruit itself plays a role in weight loss – even though we don’t know the mechanism of this action.

Nevertheless, this outcome doesn’t suggest that the grapefruit diet itself is a good way to lose weight.

In reality, the diet is just another very low-calorie diet that tries to brute force people into weight loss. Most people won’t be able to stick to the diet and of those that do, many won’t be able to keep the weight off.

Many other diets make bold claims but aren't reliable. Atrafen, the Advocare 24 Day Challenge and the Cruise Control Diet are some examples. 

If you are interested in the potential of grapefruit to contribute to weight loss, then a better approach is to include grapefruit in a healthy diet.

You can even do this if you don't want to eat half a grapefruit every day. For example, the site Minimalist Baker offers a Grapefruit Green Smoothie recipe

There is also a range of approaches that can be more effective than the grapefruit diet. These include a low carb diet, carb cycling, intermittent fasting and even the Paleo diet.

Ultimately, the most powerful approach for weight loss is to consume fewer calories than you burn. At the same time, you want to be following an approach that suits your own needs and one that you can follow in the long-term.

People vary a lot in which method works the best for them, so it’s worth taking the time to try and figure this out.

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Have you ever tried the grapefruit diet? If so, what did you think?​

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