The latest research, carried out by scientists at the Nutrition and Medical Research Centre at Scripps Clinic in San Diego, America, has found that the simple act of adding grapefruit and grapefruit juice to your diet, really can aid weight loss. But unlike the seriously restricted diet of the 80s, you get these results without changing what else you eat!
Even study leader Dr Fujioka seemed surprised, saying, ‘For years, people have talked about the grapefruit diet. Now we have data that grapefruit helps weight loss. Our study participants maintained their daily eating habits and slightly enhanced their exercise routine. The only dietary change was the intake of Florida grapefruit and grapefruit juice.’
The study included 100 obese people who were divided into three groups. The first group ate half a grapefruit before each meal three times a day. The second group drank grapefruit juice before each meal. The third group received no grapefruit. No other changes were made to their diets.
After 12 weeks, those participants who ate grapefruit with each meal lost, on average 3.6lb. Only a third of a pound a week, but pretty good considering they didn’t make any other changes to their diet. Meanwhile, those who drank grapefruit juice three times a day lost 3.3lb in the 12 weeks. By comparison, the grapefruit-free participants lost, on average, only 0.5lb.
But weight loss wasn’t the only health benefit seen when grapefruit or the juice was consumed. The research also found the grapefruit-consuming participants had lower levels of insulin, a hormone that regulates blood sugar levels and fat metabolism, which in turn might help to reduce the risk of diabetes or stroke.
The researchers believe grapefruit contains unique plant compounds that reduce insulin levels, which in turn promotes weight loss.
The link between raised insulin levels and excess weight is complicated and multifaceted. To start with, high levels of insulin may indicate that sugar isn’t efficiently utilised for energy with the result that it’s more likely to be stored as fat. Secondly, high levels of insulin can make people feel hungry so that they eat more. And finally, high levels of insulin prevent the body from breaking down fat. Add these together, and it’s easy to see why lower levels of insulin may promote weight loss. What exactly it is in grapefruit that has this insulin-lowering effect remains unclear.
Warning! Grapefruit juice can interact with medicines
While this research might tempt you to fill up on grapefruit to boost your weight loss campaign, if you’re taking any medications you might want to speak to your GP first or check the literature that comes with your medication.
This is because a wealth of research shows that grapefruit juice can interact with a number of medications, potentially causing serious side effects. It works by inhibiting an enzyme in the intestines that’s responsible for the natural breakdown and absorption of many medications. When the action of this enzyme is blocked, blood levels of these medications increase and this can lead to potentially toxic side effects.
Research suggests that flavonoids and/or furanocoumarin compounds are the substances in grapefruit juice that block the enzyme in the intestines. Many drugs appear to be affected by grapefruit juice so if you are taking any medication, it’s essential to check whether you can safely consume grapefruit juice. In the meantime, it’s likely that grapefruit segments may also interact with certain medications so you’d be wise to consult your GP before eating lots of grapefruit. Other citrus fruits don’t seem to have any effect.