What is a grapefruit?
Grapefruit is a citrus fruit originating from Barbados, currently grows on trees in Florida, California, Arizona, Australia, South Africa, Israel and India. One grapefruit contains roughly 102 calories and consists of approximately 92% water so it is also great for hydration. But how does grapefruit contribute to weight loss?
Let’s begin to say that when we exercise, we activate an enzyme called AMP-activated protein kinase (AMPK) to help muscles use the sugar and fat stores within the body as energy and fuel for exercise.
Grapefruit and weight loss
Well, a grapefruit contains an organic compound called nootkatone which activates AMPK and encourages our body to burn glucose (sugar) at rest which also boosts metabolism that leads to weight loss (Price,2017). To explain a little further, our metabolism is responsible for burning calories for energy. So when we speed-up our metabolism, our bodies will burn more calories per day at rest than usual. Therefore, we would be able to create a bigger caloric deficit than usual. Caloric deficit refers to consuming less calories than our body requires so our body will begin to use fat stores for energy. Hence why we begin to lose weight.
Grapefruit case studies
There was a study conducted by FYTEXIA-NB Consulting Group in 2008 using 20 participants with a BMI of overweight or obese persons over a period of 4-12 weeks. 10 participants were supplemented with 1.4g of SINETROL/day (which contains grapefruit extract) and the other 10 were given placebo supplementation. The results demonstrated that the group who were supplemented with SINETROL lost a significant amount of body fat, over 12 weeks they lost 15.5% and their body weight decreased by approximately 5.2kg compared to the placebo group with no major results. This shows that SINETROL which contains grapefruit could prevent obesity by decreasing BMI.
Another study conducted by the Division of Endocrinology (2006) tested the effects of grapefruit on weight and insulin resistance and their correlation to our metabolism. The study included 91 participants who were randomized into either:
- placebo (substance that has no effects) capsules and 7 ounces of apple juice
- grapefruit capsules with 7 ounces of apple juice
- 8 ounces of grapefruit juice with placebo capsule
- half a grapefruit with a placebo capsule
Each group was given these products three times a day before each meal. All the metabolic rates were tested at the start of the research and at the end of 12 weeks. The results demonstrated:
- The group who consumed the fresh grapefruit lost 1.6kg in weight
- The group who had grapefruit juice lost 1.5kg
- The group who consumed grapefruit capsule lost 1.1kg
- The placebo group lost 0.3kg.
The fresh grapefruit group lost significantly more weight and gained insulin resistance compared to the placebo group.
So is grapefruit good for fat loss?
Looking at those two studies, we can safely say that grapefruit can be a great way to jump-start your weight loss journey.
Why is grapefruit bad for you?
Before consuming grapefruit, you should also consider the possible side effects of grapefruit
- Grapefruit contains a natural chemical known as furanocoumarin which doesn’t mix well with allergy medications. If you are on medications like Claritin (loratadine) or Allegra (fexofenadine) you should avoid consuming grapefruit or grapefruit juice. I would recommend contacting your gp or a pharmacist. (Gardner, 2019)
- Grapefruit also doesn’t mix well with drugs like Viagra (sildenafil), Cialis (tadalafil) and Levitra (vardenafil) which are known for helping with erectile dysfunction. A 6-7 ounce glass of grapefruit juice is enough for drug toxicity according to a study conducted in 2013. Please check out this link to see the full list of drugs that may be dangerous to take together with grapefruit consumption.
- A study conducted in 1994 also analysed the interaction of grapefruit with Estrogens. People post menopause who consume estrogen medications are in a much higher risk of breast cancer if they consume grapefruit with Estrogens (Schubert et al, 1994). However, a follow-up study that was conducted in 2009 found no such interaction (Spencer et al, 2009). So the results are contradicting, but it may be worth taking some precautions.
So how does this actually work? Well grapefruit juice suppresses a chemical in the intestine that’s responsible for breaking down many drugs in the body. By inhibiting this chemical, the drug substance can become high in our blood stream which makes the drug more potent and toxic. (Zablocki, 2001)
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Bailey, D., Dresser, G. and Arnold, M. (2013). Grapefruit–medication interactions: Forbidden fruit or avoidable consequences?. 185(4), pp.309-316.
Dallas C, e. (2019). Lipolytic effect of a polyphenolic citrus dry extract of red orange, grapefruit, orange (SINETROL) in human body fat adipocytes. Mechanism of action… – PubMed – NCBI. [online] Ncbi.nlm.nih.gov. Available at: https://www.ncbi.nlm.nih.gov/pubmed/18617377 [Accessed 17 Jul. 2019].
Dr. Axe. (2019). Grapefruit Beats Out Anti-Obesity Drugs When It Comes to Weight Loss. [online] Available at: https://draxe.com/grapefruit-benefits-weight-loss/ [Accessed 17 Jul. 2019].
Frank, K., Patel, K., Lopez, G. and Willis, B. (2019). Grapefruit Research Analysis. [online] Examine.com. Available at: https://examine.com/supplements/grapefruit/#safety-and-toxicity [Accessed 17 Jul. 2019].
Schubert W, Cullberg G, Edgar B, et al. (1994) Inhibition of 17 β-estradiol metabolism by grapefruit juice in ovariectomized women. Maturitas; 20:155–63. Available at: https://www.ncbi.nlm.nih.gov/pubmed/7715468 [accessed 10 September 2019]
Spencer EA, Key TJ, Appleby PN, et al. (2009) Prospective study of the association between grapefruit intake and risk of breast cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC). Cancer Causes Control; 20:803–9 Available at: https://www.ncbi.nlm.nih.gov/pubmed/19224379 [Accessed on 10 September 2019]
Zablocki, E. (2001). What Could Possibly Be Bad About Grapefruit?. [online] WebMD. Available at: https://www.webmd.com/diet/news/20010105/what-could-possibly-be-bad-about-grapefruit#1 [Accessed 19 Sep. 2019].