Grapefruit diet - Everything you need to know

As a dietitian it is of my utter interest knowing the crazy diets out there, and figuring out if they actually do work or not.

I, like most people, had not heard of the Grapefruit Diet, or also known as The Chemical Diet.
So I researched, and below I will tell you what it is, what it claims to do, how to do it, the results, and if it actually does work or not.

What is it?

Kelly D. Brownell, PhD, came up with this diet in 1930, it was designed to jumpstart a weightloss, so that people would lose a lot of weight in a short period of time, and thus get motivated to continue losing weight. (Information taken from Grapefruit Diet's website)
Basically you would have to eat a grapefruit before every meal, this way you would use the fruit's enzymes to burn fat without having to go to the gym.
Since then many variations of this diet have emerged but they still keep the basic of the grapefruit before meals.
Celebrities like Brooke Shields and Kylie Minogue claim to have been successful doing this diet.

What does it claim to do?

In some places it claims to help you loose 10 pounds (4.54 kg) in 12 days, and others 1 stone (6.35 kg) in 7 days.
It is an easy weightloss, without working out or feeling hungry.
When Naringenin (the enzyme found in grapefruit that burns fat) is ingested, the body understands it is going through fasting, which will provoke the body to break down  fat.

How to do it

Here is the 7 days plan:
The following information was taken from James Duncan's blog.

11 slice dry toast

with 1 grilled tomato OR tinned tomatoes
Fresh fruit - any amount2 hard boiled eggs

Salad & grapefruit

1 boiled egg
Grilled chicken with tomatoes

Grilled steak


1 boiled egg
Fresh fruit - any amount2 grilled lamb chops

Salad & grapefruit
41 slice dry toastFresh fruit - any amount2 hard boiled eggs

Salad & grapefruit
51 slice dry toastFresh fruit - any amountFresh fish

61 glass grapefruit juiceFresh fruit - any amountGrilled chicken

Carrots & grapefruit
7Scrambled eggs

Grilled or tinned tomatoes
2 poached eggs

Grilled steak



  1. No alcoholic drinks.
  2. Permitted drinks: Black coffee, tea, lemon/grapefruit juice without sugar.
  3. No milk, butter or fats.
  5. Abstain from all not included in diet. Eat what is shown or go without.
  7. No substitutes allowed. The basis of the diet is chemical, not the quantities.
  8. Lunch and dinner may be swapped but only on the same day.


  1. The grapefruit sourness is a lot more bearable with pink grapefruit. Also, if you have a sweet tooth normally, bear in mind that grapefruit sweetens a lot in the last stages of ripening.
  2. I am used to eating like a pig, and thus had a lot of “empty stomach - must fill” type feelings. Drinking lots of water filled me up temporarily.
  3. If you are desperate for flavour on some of the blander dishes, add a little lemon juice. On the list of allowed drinks and can pep up things nicely.

Some people swear that it has worked on them and done even better, while others say they did not have any difference, and there are some that managed to lose 1 kg or so but nothing more.

Does it actually work?

Scientists have managed to find the claimed chemical that supposedly burns fat, called Naringenin.
They have also found out that the amount needed for it to actually do what it claims is to have at least 40 grapefruits in one sitting. The reason being first because it is not easily absorbed by our human bodies. Second because the concentration of it is very low in 1 grapefruit to actually break down fat.
Another issue that is obvious here, is that if you do eat the 40 grapefruits, you will also be ingesting a load of the fruit's sugar, amounting to 5.000 kcal, or 1 kg of sugar, which will clearly point out that this way you will not lose the weight, because you are adding loads and loads of unnecessary carbs in your body.
*In case you don't know, it is the excess carbs that become the stored fat in our bodies.

The scientists also figured out why some people lost weight:
1 - It makes you lose a lot of water, which obviously weighs, being so that you have not lost actual fat, but lost water.
2 - Eating the grapefruit before a meal, fills your stomach up a little bit, making you eat smaller portions of food, which will obviously make you lose weight because you are reducing food intake which equals reducing calory intake.

In other words, this diet does not do what it claims, and it does not work!

Did I give you enough information?
Are you wondering still?
Leave me a comment letting me know.


  1. This is an interesting post Paola! I've never been a fan of crash diets (I much prefer something that's sustainable in the longer run), and based on the meal plan provided (assuming you can't just eat amounts of each item) I think this is probably something that would only really work for more petite people who lead pretty sedentary lifestyles.

    There just doesn't seem to be enough calories for anything else - such a huge calorie deficit daily would surely lead to a slowing metabolism, no?

    1. Metabolism gets slower if you eat like once a day, a big meal. If you do small portions but many times during the day that accelarates the metabolism, burning quicker what you ingest. That's why the proper way to loose weight is smaller, nutritive portions around 6 times a day, if not more.
      Of course smaller portions of junk food won't help you either. Because of the high amount of trans and saturated fat you will ingest.

      Crash diets are never good, they end up harming you. Ideally you ease into a healthier lifestyle.

  2. I've heard of this diet. My mother use to do it. I cannot stomach grapefruit. I've tried adding sugar, salt, and both. Too bitter. Very, very interesting though! Great post, thanks for the info!!

    1. I like grapefruit but not enough to eat it the way this diet suggests. hehehehe

  3. Aah for me Grapefruit sums up memories of happy, warm breakfasts on holiday in France - sprinkled with copious amounts of sugar. I couldn't sully those memories by associating with a diet! Good luck to all those who can - I think I will just have to swim an extra couple of lengths in the pool.

    1. Exercise is always good, much better than crash diets!
      the sugar bit is the problem that this diet won't allow. hehehe

  4. Uh Oh! This one's not for me. I do not like grapefruit and I've cut bread out of my diet. Having said that...I'm glad to know more about it's origins as I've heard about this diet for a long time!

    1. This one should not be a diet for anyone really. Unless you enjoy what was listed there.

  5. Very interesting and informative. My personal opinion is the old fashioned way, eating healthy foods and exercise and you will lose weight.

  6. I'm not a fan of fad diets. There were too many flying around when I was in my 20's. Eating fresh food and in moderation is a better choice to be honest. Plus keeping active.

    1. There are so many flying around still. I wanted to debunk each and everyone, but there are so many that I won't be able to keep it up.


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