The grapefruit diet is one of the longest surviving so-called ‘fad’ diets which promises weight loss of as much as 10lbs in 10 days or sometimes 12 days. Sometimes known as the Mayo Clinic Grapefruit Diet (for reasons that remain unclear), it’s said to work via grapefruit enzymes that help to speed fat burning. Despite widespread scepticism, there is some evidence that it works.
What is the grapefruit diet?
The grapefruit diet involves eating grapefruit or drinking grapefruit juice before or with every meal. So far, so good – lots of vitamin C! In some versions, that’s it. In other, more strict versions, you also cut back on sugar and carbs such as white rice, potatoes and pasta, while eating more foods that are high in protein such as eggs and meat. You also drink 8 glasses of water and 1 cup of coffee per day. No quibbles from us. The only odd thing is that in some versions of the grapefruit diet, you are supposed to avoid certain foods such as celery and white onion. Erm, why? This doesn’t make sense.
Overall, the diet works because protein fills you up and cutting back on carbs reduces insulin-directed fat storing. You are also eating fewer calories – usually in the region of 800 kilocalories per day. So what about the grapefruit? Does it really help you burn fat?
Grapefruit and weight loss
Surprisingly, there is not much human research into the belief that eating grapefruit helps you lose weight, although it does seem to help lower blood pressure, improve cholesterol balance and may reduce the risk of heart disease.
In one study, a group of 74 overweight volunteers were asked to follow either a control diet without any grapefruit, or a control diet plus one half of a fresh Rio-Red grapefruit with every meal (3 times a day) for 6 weeks. Those who ate the grapefruit lost an additional 0.61kg in weight compared to those not eating grapefruit, and also lost significantly more visceral fat so their waist circumference reduced by almost 2.5 centimetres.
A recent review of all the evidence, published in 2017 assessed the results from 3 clinical trials involving 250 overweight volunteers. They concluded that eating grapefruit failed to produce a significant difference in weight loss, although those eating grapefruit did lose, on average, 1 lb (0.45 kg) more than those not eating grapefruit, and also benefitted from a small but significant decrease in systolic blood pressure (upper reading) of 2.43 mmHg. They did add that lack of trials, short durations and no established minimum effective dose limited their ability to draw any firm conclusions and that more research into the weight loss effects of grapefruit is needed.
So, eating grapefruit may help you lose an additional 1 pound in weight, possibly by providing a low-calorie source of fibre and fluid to fill you up. As an appetiser, grapefruit is satiating so you eat less food at the same meal. Its acidity also reduces sweet cravings. The fact that people eating grapefruit lost 2.5cm more around their waist may suggest that grapefruit might help you melt fat by stimulating fat burning.
Grapefruit does burn fat AND sugar
Grapefruit contains a range of polyphenols, including high concentrations of naringenin, a bioflavonoid which gives grapefruit its distinctive, bitter taste. Scientists have found these polyphenols stimulate the rate at which muscle, adipose (fat) and liver cells burn both fat and glucose – no grapefruit enzymes are involved!
Naringenin has a number of beneficial antioxidant effects, damping down inflammation, lowering cholesterol, improving glucose control and may even have an anticancer action. Naringenin is structurally similar to resveratrol, the black grape antioxidant that is known to activate a protein (SIRT1) that boosts metabolism and speeds fat burning. Researchers therefore investigated to see if naringenin could do the same.
First, they found that naringenin stimulates skeletal muscle to take up glucose and significantly increased their production of energy. Then, they confirmed that naringenin stimulates fat cells to burn fat.
Latest research shows that naringenin regulates energy balance and ‘robustly’ prevented obesity in mice fed a high fat diet. Naringenin was found to switch on genes that burn fat in white adipose tissue (WAT) and also stimulated fat burning in the liver to reduce fatty liver changes and improve insulin resistance.
So there you have it. The Grapefruit diet may have something going for it after all!
NB Grapefruit naringenin interferes with the action of enzymes that break down some prescribed drugs, especially statins, antihistamines and some blood pressure medications. If you are on any medicines, read the Patient Information Leaflet or check with your doctor or pharmacist to see if you are able to combine them with grapefruit or grapefruit juice.
Grapefruit Diet Plan
- Eat half a pink or red grapefruit before each of your 3 main meals per day – these have significantly more naringenin than blond grapefruit (but those will do at a pinch).
- Follow a high protein diet – eggs, beans, chickpeas/garbanzo beans, fish, chicken, turkey, with some red meat but have smaller than usual portions.
- Dairy foods are fine (butter, cream, cheese, milk, crème fraiche, yogurt).
- Eat LOTS of non-starchy vegetables – green leaves, tomatoes, cucumber, cabbage, kohl rabi, aubergine/eggplant, courgette/zucchini, green beans, sweet potatoes and mushrooms and so on.
- Have additional fruit for snacks and desserts – berries, grapes, apples, mandarins, peaches, nectarines, plums.
- Drink plenty of fluids – water, tea, herbal teas, one or two cups of coffee per day.
- AVOID sugar and artificial sweeteners – use Stevia for sweetness.
- Cut right back on carbohydrate rich foods (bread, pasta, rice, grains, white potatoes)
- Avoid alcohol.
This program is usually followed for 10 to 12 days, and then restricted foods are slowly reintroduced. Have you followed the Grapefruit diet? Did it work for you?