I’m sure that everyone knows about the weight loss effects and how the juice can alter certain medications. BUT… does anyone know how much juice to drink to have the maximum weight loss effect? When should you drink it, before meals, during meals, after meals, mornings, before going to bed? Is white juice better than red or is red the best? Curious about how everyone knows about it but no one knows the details!
to be blunt, most juice is liquid sugar and pretty much useless nutritionally if you want to try to lose weight. It may have some spiffy vitamins in it, but you would be better off just eating the piece of fruit and getting the added fiber in your diet.
There is nothing in grapefruit juice that will boost a metabolism. At best it will fill you up a bit if you drink it just before eating so you dont have that second helping of chocolate cake for dessert.
If you want to drink something to lose weight, choose a nutritionally null beverage like water with a tiny splash of lemon or lime juice for flavor and drink it whenever you get the urge to have a snack.
As I understand it, fruit juice drinks are really not good for people with weight problems, especially if they’re sweetened with sugar or corn syrup. Are you familiar with the glycemic index?
If you insist on having it, go with something that’s unsweetened, has the pulp in it, and drink with a meal to spread out the insulin response.
Hint: be very skeptical of anything that “everyone knows.”
All fruit juices are high in the Glycemic Index, so not very effective for weight loss. Though grapefruit is not as bad as most others, it’s still something you don’t need if you’re trying to lose weight.
Grapefruit is famous with the “as seen on TV” crowd as having miracle powers Total BS.
Eat a grapefruit, drink some water. If you are going to get calories, it’s better to chew them.
I remember this study, which seems to be legitimate to me, which found eating 1/2 a grapefruit before each meal (assuming a 3-meal-a-day diet) and changing nothing else averaged a weightloss of 3.6 pounds over 12 weeks on a sample of 100 people.
And here’s the key line from the summary of that study:
*"Although the mechanism of this weight loss is unknown it would appear reasonable to **include *grapefruit in a weight reduction diet." (bolding added).
That’s how any weight loss aid is marketed these days - if it’s used as part of a comprehensive diet and exercise plan, you’ll see results!
There’s no known Super Magic in grapefruit. Eat it as part of your veggie and fruit intake, and be careful about eating too much of it because it can interfere with the action of a number of medications.
As I understand it, the theory behind the glycemic index and insulin resistance stuff goes like this…
Used to be, we ate lots of unrefined foods. Take flour, for instance: it used to be stone ground and was pretty coarse. Much of the bran and other parts were left in. The good thing about this was that it your digestive tract worked on that longer so you ate and didn’t get hungry again soon.
Now we have super refined things like cake flour…you eat it and it releases energy quickly, like a sugar bomb, triggers insulin, passes through you quickly, and leaves you hungry. You eat more, triggering still more insulin.
But when eating a grapefruit, you’re also talking about eating pulp, which takes up space in your stomach and satisfies you longer. Unfortunately many juices are pulp-free. If sugar or corn syrup are added to sweeten, they’re even worse.
Pick up a box of the worst cereal on the market and it will probably say something like “Part of a complete breakfast.” I.e. if you eat 8 other healthy things with this, you’re good to go because this isn’t doing a thing for you, nutritionally.
I don’t think it’s a miracle cure, and I don’t do it. But the only difference between the two groups, according to the study, was whether one group took in grapefruit or not, and those results were apparently statistically significantly higher than those taking placebos. I mean, it’s not like the grapefruit group exercised and the non-grapefruit group didn’t. It seems to me that something is going on there.
This has nothing to do with weight loss, but a word of caution regarding grapefruit and grapefruit juice.
There is(are) a chemical substance(s) in grapefruit which inhibit(s) your body from breaking down various medications. The chemicals in grapefruit responsible for this are probably furanocoumarins. In any case, people who eat grapefruit or who drink grapefruit juice are at risk of having the medicines they’re taking build up to toxic levels which, in turn, can be fatal. This is especially the case for people who don’t usually have grapefruit or grapefruit juice but suddenly begin taking it (for things like, say, dieting).
Some of the drugs whose breakdown is inhibited by grapefruit include many anti-HIV drugs, medicines used to treat fungal infections, cholesterol lowering drugs (‘statins’), certain antidepressants, methadone, and various antibiotics. In other words, there is a LOT of potential for interaction.
The right hand column of the first table here (labeled ’ substrates’) lists drugs whose breakdown is inhibited by grapefruit. People taking any of those drugs should avoid grapefruit unless/until they’ve cleared it with their specialist. And, for those who want to know a bit more about this issue, here’s a recent and readable article. There’s lots more out there if you’re interested.
The “something” is that they ate something very high in indigestible fiber, high in liquid (ie, “filling”), and low in calories right before eating their main meal. They were already somewhat full from something low in calories before they began eating higher calorie foods. That doesn’t seem like black magic to me.
You get the same results eating a cup of vegetable soup before eating your main meal. Not from any magical property of vegetable soup - its just fiber and water.
I would think if it were that simple, the scientists in charge of the experiment would have figured that out. Note that the experiment was done with placebos of apple juice instead of grapefruit juice, and that the grapefruit juice yielded extra weight loss the apple juice didn’t.
Thanks to all for the factual answers in this thread, or answers as close to factual as we’re going to get.
pulkamell (you rock!) came up with the info I was seeking. I already knew that grapefruit juice was no miracle; by drinking it I will not look like Mr. Universe overnight or wake up every morning with a woody that a cat couldn’t scratch. 
I like all juices… just juice, no added sugar or raisins or fruitbats or orangutans. If grapefruit juice will be of assistance in weight control, I should learn how much and when to consume it and , above all, can I afford to purchase it to get the results I want.
To be honest, I am cautious about that study. On the face of it, it looks pretty legitimate and it looks like there’s something to the grapefruit thing. However, I’d be curious to see if these sorts of results were duplicated by any other researchers.
At the very least, it doesn’t look like eating half a grapefruit before every meal is going to hurt your diet results. And, of course, individual results may vary. Hey, combine it with the soup research, and see what happens. 
What weight loss effects? I’ve heard people with weight problems complaining about drinking juice because it could make them put on more weight (sugar)…and I have no idea what it does to medications. What gives?
Some posts in this thread are misleading.
Maybe this will help clear some things up…
Grapefruit juice is not the same thing as juice with added sugar!
Juice is juice, Juice with added sugar is juice with added sugar.
They are NOT the same thing.
Juice is LOW on the glycemic index. Juice with added sugar is HIGH on the glycemic index.
Just so we’re comparing/contrasting the same things.
PURE JUICE is packed with sugar. Pure orange juice, fresh squeezed, with no sugar added, has the same amount of sugar per unit volume as Coca-Cola. (27g sugar per 8oz).
Grapefruit juice, freshly squeezed, with no sugar added, has around 22g of sugar per 8 oz.
That Scripps study seems to be cited quite a bit on various diet and “natural cure” sites.
I haven’t yet read the full paper, but what strikes me from the abstract, aside from the small numbers of participants in each arm of the study (91 people total) and the short followup period (12 weeks) is that it apparently was not really a placebo-controlled study.
There is no way, for instance, that people drinking apple juice didn’t know what the stuff was, or that the grapefruit juice people were unaware of what they were consuming, or that you can eat half a grapefruit and not know what it is. If you’ve heard that grapefruit is a weight loss aid, you might very well subconsciously adjust your food intake or other lifestyle factors so that the grapefruit/grapefruit juice comes out looking like a significant factor (the change in insulin resistance is interesting, but is not the same as losing weight).
It sound like they’d have gotten more meaningful results if there was a true double-blind study where neither the researchers or the participants knew what was being administered (it’d have to be something like identical capsules with grapefruit extract or placebo).
The key to weight loss is two simple yet very difficult things - take in fewer calories, and exercise to burn off more of them. You can eat grapefruit, or take Brother Billybob’s Super Fat Burner Formula or any of a thousand different weight loss aids, and they’ll all work - if you also eat less and burn off extra calories.
Nobody is saying that juice = juice + sugar. And nobody is denying that unsweetened juice has a lower GI than sweetened juice. But ALL fruit juice, even unsweetened, has plenty of sugar, which someone on a weight-loss diet doesn’t need.
And regarding the study: the only way it could have any validity would be if the people in the two groups ate precisely the same meals, so the only variable would be the grapefruit. I doubt this was the case. Plus the fact that the study was obviously not double-blind.