Grapefruit And Weight Loss: Fact Or Fiction

  • Duyen NguyenMaster in Science - MSci Human Biology, University of Birmingham

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Overview

The social pressure to conform to beauty standards and have the ideal body type has resulted in the continued prevalence of fad diets and diet myths. These diets promote miracle weight-loss foods, such as grapefruit, which are supposed to have fast results when implemented into your daily food plan.

The grapefruit diet is arguably one of the most renowned and disputed among these fad diets. It dates back to the 1930s and is often referred to as the “Hollywood” diet due to its popularity and the influence it garnered from celebrities. This diet is claimed to work on the basis that grapefruits contain “fat-burning” enzymes that enable rapid weight loss. Despite lacking scientific evidence to back these claims, it remains a prominent diet myth and continues to attract followers. 

In this article, we will explore whether grapefruits can effectively manage weight and their alternative health benefits. Is there any truth to this diet myth? Or is the grapefruit diet purely fiction?

What is the grapefruit diet?

The grapefruit diet comes in many variations. Most of these share a common theme: a severe calorie deficit. A typical grapefruit diet comprises protein-rich meals with grapefruit or grapefruit juice incorporated into them. Supporters of the diet contend that grapefruit aids in fat metabolism, facilitating swift reduction in body weight. They claim you can undertake this diet for 10-12 days and lose 10 pounds within this short timeframe. Most versions also suggest cutting down your daily calorie count to only 800-1000 calories. This is extremely harmful and significantly lower than the recommended daily intake (2,000 for people assigned female at birth and 2,500 for people assigned male at birth).1

Does grapefruit “burn” fat?

Grapefruits have many beneficial properties, however, containing “fat-burning” enzymes is not one of them. There is insignificant research to support the claims that grapefruits target fat deposits or increase your metabolism. Instead, studies have shown that calorie restriction has a counterproductive effect of reducing your metabolic rate.2 This occurs because your body detects the lower food intake and, in turn, reduces your metabolism (the rate at which you burn calories). Other negative side effects from calorie restriction include weakening of bones, muscle loss, fatigue, and nutrient deficiencies.3,4,5,6

In regards to the diet’s rapid weight-loss claims, this is a consequence of severe calorie reduction. Yes - this lower-calorie diet may lead to temporary weight loss. However, it is not successful for long-term, sustainable results. The initial weight you lose is likely to be gained back, as expected with any fad diet.

To lose weight, you need to increase your energy expenditure so it is higher than the amount of energy you consume through food. The best way to achieve this is to slowly introduce a healthier, balanced diet and increased physical activity. Making these appropriate lifestyle changes can support a long-term and more beneficial approach to losing weight without the need to adopt any restrictive behaviours. 

Can grapefruit suppress your appetite?

Although there is limited research to state that grapefruits are effective for weight loss. Most of these trials have been criticised for their moderate quality.7 Factors such as the low numbers in controlled trials, short durations of interventions, and lack of established guidelines for the consumption of grapefruit make it unreasonable to draw any conclusions about the fruit’s effectiveness. 

Nevertheless, grapefruits may still be used to manage your weight due to their high fibre and water content.8 Eating grapefruit with your meals may cause you to feel fuller as a result of its fibre- and water-rich content. This dietary method is often referred to as “preloading”. 

Health benefits of grapefruit

High nutritional profile of grapefruit

Although, we advise against following the grapefruit diet. Don’t let this put you off incorporating more grapefruit into your meals. Overall, grapefruits are highly nutritious and a great source of vital nutrients that can improve your health. 

Grapefruits contain the following essential nutrients:

  • Vitamin C
  • Vitamin A
  • Fibre
  • Magnesium
  • Potassium

Grapefruits are an excellent source of vitamin C. It contains over 60% of your recommended daily vitamin C intake levels. Vitamin C is an antioxidant; they have properties that strengthen your immune system by preventing cell damage. 

Vitamin A is fundamental for eye health and improves your immune system by protecting against inflammation.9 Grapefruits are said to provide over 50% of your required vitamin A intake.

Consumption of grapefruit has been shown to increase the intake of fibre, magnesium, and potassium. On the whole, a diet rich in the listed nutrients is associated with longevity and reduced risk of many chronic diseases such as heart disease and type 2 diabetes.

Lowers risk of cancer and cardiovascular disease

Like other citrus fruits, grapefruits are rich in vitamin C, an antioxidant known to prevent cell damage. Research has suggested that high amounts of vitamin C in your diet can reduce cancer risk.10

In addition to lowering cancer risk, grapefruits have been proposed to protect against vascular disease and strokes. This is because they contain potassium and fibre.11 Fibre-rich foods have been shown to reduce inflammation, reduce cholesterol, and help maintain normal blood pressure levels. Potassium is also reported to help lower blood pressure levels.

Helps to maintain blood sugar levels

Eating grapefruits can help manage your blood sugar levels due to their low glycaemic index (GI). Foods with low GIs break down more slowly, allowing for a gradual elevation in blood sugar levels. Research has also provided evidence to suggest grapefruit may help improve insulin resistance. 

High water content

Grapefruits are a great source of hydration as they are high in water content (approximately 88%). The Eatwell Guide recommends 6 to 8 glasses of water a day. However, bear in mind, that water should be your primary source of daily fluid intake, as excessive consumption of acidic fruits may result in tooth damage. 

Potential risks and side effects

Erosion of tooth enamel

Just like other citrus fruits, grapefruits are rich in citric acid. Excessive consumption may cause tooth enamel erosion.12 For anyone with sensitive teeth, mindful consumption is advised to avoid potential tooth damage.

Medicines affected by grapefruit

Various studies have shown that grapefruits may interfere with medications and cause adverse effects. 

Medicines affected by grapefruit are:

  • Some statin drugs (e.g., Simvastatin and Atorvastatin)
  • Some calcium channel blockers (e.g., Amlodipine and Felodipine)
  • Some anticoagulants or antiplatelet medicines (e.g., Warfarin and Clopidogrel)
  • Cyclosporine and immunosuppressants 
  • Entocort
  • Cytotoxic medicines 

The NHS website has a list of medicines that are affected by grapefruit. However, this is not an exhaustive list. Keep in mind that drug interactions will vary between individuals, so always seek advice from your GP or pharmacist first.

FAQ's

Does grapefruit burn fat?

No - this is scientifically untrue. Grapefruits are marketed to have “fat-burning” enzymes but there is limited evidence to prove that grapefruits or any food has properties that burn fats. Nonetheless, do not let this deter you! Grapefruits have many other health-associated benefits, such as strengthening your immune system. You can implement this fruit into your diet to improve your overall health. 

What is the theory behind the grapefruit diet?

Followers of the grapefruit diet believe that grapefruits contain fat-burning enzymes that burn fat. This is false. That said, grapefruits can potentially suppress your appetite leading to subsequent weight loss. This occurs as a result of their high fibre and water content.

While this may be desirable, rapid weight loss is often short-term and unsustainable. It is recommended to diversify your diet by incorporating a variety of healthy foods instead. A balanced diet, in conjunction with physical activity, will better help you achieve your long-term goals. Consulting your GP and dietitian is also advisable.

What are the side effects of grapefruit?

Consuming too much grapefruit may lead to tooth erosion and damage. This is due to the high acidity of the fruit. In some individuals, high levels of vitamin C can result in minor gut health issues such as diarrhoea, nausea, and stomach cramps. Grapefruits can also have harmful interactions with certain medications. Please seek further medical advice via your GP to prevent any adverse effects. 

Summary

Ultimately, you should still consider adding grapefruits to your meal plans. These fruits are highly nutritious and can contribute to improving your health in a multitude of ways. However, should you solely rely on grapefruit as a weight-loss tool? The short answer is no.

The grapefruit diet promotes short-term and unsustainable weight loss that does more harm than good. It is recommended to opt for a more balanced lifestyle to manage your weight instead of following restrictive fad diets. More research is warranted to prove grapefruits are effective for losing weight, but for now, there is not enough evidence to suggest grapefruits possess any special fat-burning qualities. 

References

  1. Osilla EV, Safadi AO, Sharma S. Calories. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Mar 18]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK499909/.
  2. Most J, Redman LM. Impact of calorie restriction on energy metabolism in humans. Experimental Gerontology [Internet]. 2020 May [cited 2023 Dec 15];133:110875. Available from: https://linkinghub.elsevier.com/retrieve/pii/S0531556519308642
  3. Veronese N, Reginster JY. The effects of calorie restriction, intermittent fasting and vegetarian diets on bone health. Aging Clin Exp Res [Internet]. 2019 Jun [cited 2023 Dec 15];31(6):753–8. Available from: http://link.springer.com/10.1007/s40520-019-01174-x
  4. Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. Int J Obes (Lond) [Internet]. 2010 Oct [cited 2023 Dec 15];34(0 1):S47–55. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673773/
  5. Winwood-Smith HS, Franklin CE, White CR. Low-carbohydrate diet induces metabolic depression: a possible mechanism to conserve glycogen. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology [Internet]. 2017 Oct 1 [cited 2024 Apr 16];313(4):R347–56. Available from: https://www.physiology.org/doi/10.1152/ajpregu.00067.2017
  6. Damms-Machado A, Weser G, Bischoff SC. Micronutrient deficiency in obese subjects undergoing low calorie diet. Nutr J [Internet]. 2012 Jun 1 [cited 2023 Dec 15];11:34. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404899/
  7. Onakpoya I, O’Sullivan J, Heneghan C, Thompson M. The effect of grapefruits (citrus paradisi) on body weight and cardiovascular risk factors: A systematic review and meta-analysis of randomized clinical trials. Critical Reviews in Food Science and Nutrition [Internet]. 2017 Feb 11 [cited 2024 Apr 16];57(3):602–12. Available from: https://www.tandfonline.com/doi/full/10.1080/10408398.2014.901292
  8. Parretti HM, Aveyard P, Blannin A, Clifford SJ, Coleman SJ, Roalfe A, et al. Efficacy of water preloading before main meals as a strategy for weight loss in primary care patients with obesity: RCT. Obesity [Internet]. 2015 Sep [cited 2024 Apr 16];23(9):1785–91. Available from: https://onlinelibrary.wiley.com/doi/10.1002/oby.21167
  9. Maxfield L, Daley SF, Crane JS. Vitamin C Deficiency. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 [cited 2024 Mar 18]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK493187/.
  10. Mora JR, Iwata M, Von Andrian UH. Vitamin effects on the immune system: vitamins A and D take centre stage. Nat Rev Immunol [Internet]. 2008 Sep [cited 2024 Apr 16];8(9):685–98. Available from: https://www.nature.com/articles/nri2378
  11. Murphy MM, Barraj LM, Rampersaud GC. Consumption of grapefruit is associated with higher nutrient intakes and diet quality among adults, and more favorable anthropometrics in women, NHANES 2003-2008. Food & Nutrition Research [Internet]. 2014 May 8 [cited 2023 Dec 15]; Available from: https://foodandnutritionresearch.net/index.php/fnr/article/view/671
  12. Chen Z, Huang Y, Cao D, Qiu S, Chen B, Li J, et al. Vitamin c intake and cancers: an umbrella review. Frontiers in Nutrition [Internet]. 2022 [cited 2023 Dec 15];8. Available from: https://www.frontiersin.org/articles/10.3389/fnut.2021.812394

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Duyen Nguyen

Master in Science - MSci Human Biology, University of Birmingham

Duyen is a creative and enthusiastic writer with an MSci in Human Biology. She has an extensive scientific background and is highly proficient in cancer biology and Drosophila genetics. Her research project investigated the importance of calcium transporters, Itpr and SERCA, in the regulation of apoptosis-induced proliferation. She is an aspiring medical writer and strives to create accessible and engaging content that effectively translates research to a range of audiences.

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