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The Grapefruit Diet and Weight Loss: A Keto Perspective

The Grapefruit Diet and Weight Loss: A Keto Perspective

by Lily Harmon -

The thought of a grapefruit diet that is nostalgic, reminiscent of the early 80s and the days of Jane Fonda's workout videos, high-waisted vibrant leotards, and ubiquitous bright pink cans of Tab diet soda. Yep, we here at Konscious Keto remember those days well.

But the days of über-specific fad diets like the cabbage diet, the sexy pineapple diet, and yes, the grapefruit diet, has long faded.

The premise of subsisting on single ingredients or adding in copious amounts of certain foods have fallen from favor in the health and fitness space, replaced with more balanced food plans like the ketogenic or paleo diets.

Delving deeper into nutrition and the way different foods affect our body is a worthy exercise. The better we understand the benefits of the foods we eat, the more we are empowered to let our medicine be our food.

The grapefruit diet of years past promised increased fat loss by just eating half of the fruit before every meal, but was that advice helpful or harmful, long-term?

Also, if there is an added benefit to the approach followed with a grapefruit diet: could there be a unique benefit when executed through a ketogenic framework, or not? Should we ditch this fad diet for good altogether?

What is the Grapefruit Diet?

Primarily, a grapefruit diet advises eating the fruit before every meal and would look something like this:

  • Limit sugar intake, refined carbohydrates, and starches
  • Eat more foods rich in healthy fat and protein
  • Eat eggs and bacon for breakfast
  • Nosh on a salad with protein for lunch
  • Pack your plate with non-starchy vegetables and protein for dinner
  • Nightcap: a glass of tomato juice or skim milk
  • Eat ½ grapefruit with every meal, or 4 oz. of 100% grapefruit juice (many brands contain added sugar)

But is consuming this citrus fruit every day, possibly several times a day, worth the glucose impact?

And does eating grapefruit possess any additional thermogenic effect to help boost fat loss, along with metabolic ketosis?

The grapefruit diet approach may produce some weight loss initially because it drastically restricts calories, but there are more sustainable ways to achieve accelerated weight loss—especially on any variation of a ketogenic diet.

The Science Behind The Grapefruit Diet

Simply put, the idea of the grapefruit diet is that you consume 1/2 a grapefruit or grapefruit juice before each meal, and bingo—you’ll lose weight.

It sounds too good to be true, but let's take a look at some of the science that has sustained the allure of this diet since the 1930s to see if there are any possible benefits before we cancel the idea altogether.

Flavonoids for Weight Loss

Don't get us wrong; grapefruit contains powerful phytonutrients called flavonoids and the health benefits they provide make adding the fruit into your meal plan, even if it doesn't significantly impact weight loss, worth considering.

Flavonoids are known to offer a broad range of benefits from boosting heart health to reducing oxidation, to providing anti-inflammatory and anti-carcinogenic properties—helping to fight against cancer!

To this point, naringin is an especially beneficial type of flavonoid found in high concentrations in grapefruit, and some emerging evidence shows that it can aid in treating obesity, diabetes, and metabolic syndrome.

Interestingly, recent studies have shown a significant increase in fat loss, for test group participants following the grapefruit diet protocol. All experienced significant weight loss, especially compared to their placebo group. But is it the grapefruit causing the weight loss directly, or as a side effect?

Fiber and Water for Weight Loss

More than grapefruit being a magical food, the increased weight loss witnessed in those eating this citrus fruit every day may be more associated with its high water and fiber content, which leads to satiety and may curb overeating.

Also, grapefruit is pretty low on the glycemic scale and appropriate on a ketogenic diet as it won't spike glucose when eaten in moderation.

Consider adding grapefruit to your meal plan for more variety, but keep an eye on creating a caloric deficit and generally consuming low-glycemic foods if weight loss is the goal.

Nootkatone for Weight Loss

In addition to containing a rich profile of flavonoids, grapefruit is abundant in the essential oil, nootkatone. This oil, with its quirky name, is responsible for the fresh citrus scent you smell when you cut into this ripe fruit.

Although research around the benefits of this oil is preliminary, initial findings show improved glucose regulation and obesity prevention when studied long-term in mice—a hopeful discovery for its potential benefits in humans.

Can the Grapefruit Diet Burn Fat?

Champions of a grapefruit diet tout its potential to torch additional calories and aid in accelerated weight loss, but there are a few significant problems with this diet:

  • You’re losing mostly water weight, not fat
  • Fad dieting doesn’t work long-term
  • Drastic calorie restriction disrupts healthy hormone function
  • Massive consumption of grapefruit will disrupt ketosis

Again, including grapefruit in small amounts is feasible on a ketogenic diet as it has a relatively low glycemic load per fruit—landing at 25 on the index—but following a strict grapefruit diet seems unsustainable long-term for a few reasons, more on that below.


Again, crash dieting can result in a fast and significant drop on the scale, but please be clear: at least some of that 'weight' loss is water, not fat.

One tell-tale sign that a drastic drop on the scale was a loss of water is, once you begin eating regularly again, the number on the scale starts to creep back up, quickly.

If it's any consolation the opposite is also true, so when you overdo it with eating one day, and the scale jumps 1-5 pounds overnight, know that it is likely the body storing additional water weight and not the gaining of pure body fat.


Drastically reducing and restricting calories as is the approach with crash diets is traumatic to the body, causing a level of metabolic shock.

And crash diet models that encourage severe calorie restriction in the absence of consciously eating adequate amounts of healthy fats, can pose problems in the body long-term.

Furthermore, studies have shown that crash diets cause mood instability and crankiness, leveling a blow at your mental health.

Also, the body is geared toward self-preservation and will react if food is limited to dangerous levels, even leading to disorders like anxiety, depression, mood swings, and hormonal dysfunction!


This point also speaks to why we advise fasting for shorter windows if female; as extended fasting windows can wreak havoc on hormonal health, disrupting the function of many body functions.

Specifically, the disruption of the hormone leptin, our satiety hormone, is caused by severe calorie restriction—damaging signals that inform us we're full and eventually leading us to overeat and potentially gain weight.

Conversely, a ketogenic diet is a much healthier approach because it encourages eating a balanced diet constructed through a low-carb, high-fat dietary framework—the lifestyle is never about deprivation or excess.

Use a free app calculator like that provided by MyFitnessPal to determine your ideal caloric target, as well as the perfect amounts of fat, protein, and carbs to eat each day, in order to hit your weight-loss objectives.


Eating a quarter grapefruit here and there, coming in at around 6.25 grams of carbs a serving can easily fit into a ketogenic protocol.

But eating grapefruit in the amounts advised per a grapefruit diet will quickly raise glucose levels high enough to compromise ketosis, triggering the body to run on glucose as opposed to fat and ketones for fuel.

Besides, blood sugar and insulin regulation are essential for fat loss, so spiking your blood sugar before every meal is purely counter-productive if you're trying to avoid type 2 diabetes, insulin resistance, or want to lose weight.

You're much better off incorporating clean and low-glycemic keto meal replacements, like Keto Shake, into your diet to crush sugar cravings and boost ketone production, to facilitate nutritional ketosis and accelerated fat loss, naturally.

Potential Dangers of Grapefruit Diet

In addition to having possible adverse effects on hormone health, blood sugar, and metabolism, the grapefruit diet appears to pose some additional risks, and you should be aware.

Drug Interactions

It appears to be an innocent citrus snack, but some components in grapefruit can have dangerous interactions with certain pharmaceutical compounds—possibly leading to liver damage or magnified side effects from allopathic medications.

Grapefruit may interfere with the following medications:

  • Statin medications like Lipitor and Zocor
  • Anti-anxiety medications like Buspirone
  • Corticosteroids like Entocort and Uceris
  • High blood pressure medications like Procardia
  • Organ transplant rejection medications like Sandimmune
  • Antihistamines like Allegra
  • Arrhythmia medications like Pacerone and Nexterone

Discuss the consumption of grapefruit with your doctor to determine whether eating this fruit could have dangerous effects, given your current medical condition.


Drinking 250 ml of grapefruit juice a day is linked with an increased risk of kidney stones. And the contrast between the limit suggested for health reasons compared to that advised with a grapefruit diet is alarming!

Consider this; a grapefruit diet recommends drinking four ounces of grapefruit juice three times a day—far exceeding the suggested daily limit coming in at 354 ml!

Is Grapefruit Keto?

Although it is possible to incorporate grapefruit into a ketogenic diet, it is higher on the GI scale than low-carb berries, and those carbs can add up quickly—kicking you out of ketosis.

A better bet is comprising your diet of lower-glycemic fruits (e.g., blackberries, strawberries, and blueberries, etc.) to prevent spiking glucose levels, disrupting metabolic health, and compromising nutritional ketosis.


The grapefruit diet fad is one we suggest shelving, along with mullets and bright blue eye shadow—resign it to the days of disco and focus on a more progressive plan to create sustainable weight loss via a ketogenic diet.

Comprise your diet of organic, whole foods like fatty fish and dark leafy greens or grass-fed beef and fermented veggies; and keep the carbs low, and the options vary, so you never get bored.

Sticking to well-established approaches to long-term weight loss, like that found in an adequately composed keto protocol, is a wise and stress-free way to improve health, shed excess weight, and keep glucose levels in check, all while enjoying some of the most delicious low-carb, high-fat food around—so, happy eating to you!

Keto Sources

  1. Alam, M. A., Subhan, N., Rahman, M. M., Uddin, S. J., Reza, H. M., & Sarker, S. D. (2014). Effect of Citrus Flavonoids, Naringin, and Naringenin, on Metabolic Syndrome and Their Mechanisms of Action. Advances in Nutrition,5(4), 404-417. doi:10.3945/an.113.005603
  2. Benton, D., & Young, H. A. (2017). Reducing Calorie Intake May Not Help You Lose Body Weight. Perspectives on Psychological Science,12(5), 703-714. doi:10.1177/1745691617690878
  3. Fernández-Elías, V. E., Ortega, J. F., Nelson, R. K., & Mora-Rodriguez, R. (2015). Relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans. European Journal of Applied Physiology,115(9), 1919-
  4. Fujioka, K., Greenway, F., Sheard, J., & Ying, Y. (2006). The Effects of Grapefruit on Weight and Insulin Resistance: Relationship to the Metabolic Syndrome. Journal of Med
  5. Murase, T., Misawa, K., Haramizu, S., Minegishi, Y., & Hase, T. (2010). Nootkatone, a characteristic constituent of grapefruit, stimulates energy metabolism and prevents diet-induced obesity by activating AMPK. American Journal of Physiology-Endocrinology and Metabolism,299(2). doi:10.1152/ajpendo.00774.2009
  6. 1926. doi:10.1007/s00421-015-3175-zPark, H., & Ahima, R. S. (2015). Physiology of leptin: Energy homeostasis, neuroendocrine function, and metabolism. Metabolism,64(1), 24-34. doi:10.1016/j.metabol.2014.08.004
  7. Pu, P., Gao, D., Mohamed, S., Chen, J., Zhang, J., Zhou, X., . . . Jiang, H. (2012). Naringin ameliorates metabolic syndrome by activating AMP-activated protein kinase in mice fed a high-fat diet. 
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