I love grapefruit and have eaten it on and off for several years depending on seasons. Recently I have come across several different claims that grapefruit help you burn fat and things like "If you eat one grapefruit per day for a whole month you will lose 3kg."
closed as off topic by Ivo Flipse♦ Feb 22 '12 at 18:42
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Not exactly. However, below are 2 studies looking at grapefruit consumed prior to meals. They look at weight loss, as well as health factors like cholesterol and insulin resistance. (Note: these are not what is typically thought of as the "grapefruit diet".)
The study found that it didn't matter whether the grapefruit was in the form of fruit or juice, (even water achieved the same weight loss) as long as they were "pre-loaded" meaning consumed before the meal. With the preloading:
The one health benefit that the GF and GFJ did show over the water preload was the improvement in HDL.
So with this study, it was the preloading, whether with water, juice or fruit, that increased the weight loss of people on a calorie reduced diet (who were also wearing a pedometer).
However, if you are interested in improving your HDL levels, adding grapefruit or grapefruit juice prior to meals will help according to this study.
I only have access to the abstract which does not compare half of a fresh grapefruit with any other fruit.
Cons: Grapefruit does have the potential to interact with drugs. WebMD cautions pregnant women, postmenopausal women, or women with breast cancer about drinking excessive amounts of grapefruit juice or taking grapefruit supplements. I don't know of any studies with eating more than one and a half grapefruits per day.
You can refer this WHFoods page about grapefruit, it is very detailed about the benefit of eating grapefruit. Check about the result of overdose nutrients here. And please don't consume drug with grapefruit, it is very dangerous, please refer to the page about grapefruit.
By the way, World Healthiest Foods is a very good site about healthy food.