Wouldn’t it be lovely if there were foods you could eat that would actually help you burn calories? Many people believe that grapefruit is one of them. In fact, some diet experts not only endorse eating fresh grapefruit, they also recommend ‘grapefruit pills’, which usually contain a grapefruit constituent called naringin.
The diet-boosting properties of grapefruit are just a half-truth. Grapefruit may be tied in some way to better weight loss, but scientists are not sure how. We found one scientific study from the Scripps Clinic in California in which obese patients who consumed half a fresh grapefruit before meals, three times a day, lost more weight than those who took placebo pills and apple juice, grapefruit pills and apple juice, or placebo pills and grapefruit juice. The increased weight loss was in the range of one to two pounds or more over twelve weeks. The obese patients who had metabolic syndrome (their bodies are somewhat resistant to the effects of insulin) also seemed to lose more weight with the grapefruit juice or grapefruit pills than if they had a placebo pill.
The investigators running the study concluded that grapefruit should be part of a weight-reduction diet, even though they did not know why it was having these effects. The patients who ate grapefruit may have changed their behaviour or altered their diets in ways that the study did not measure.
Other studies and expert panels have concluded that grapefruit does not burn fat in any unusual way. The American Dietetic Association states that ‘this long-held myth is just wishful thinking. Digestion of any food uses a small amount of energy. But no food – or food component – can ‘burn up’ the calories in food or ‘melt away’ body fat. If you lose weight when you add grapefruit to your eating plan, it’s probably because you’re substituting it for another food that has more calories.’
Another theory supporting the use of grapefruit in the diet is the ‘thermic’ effect. If a food has a thermic effect, it increases how much energy the body burns up after that food is eaten, or how many calories are needed to digest the food eaten. The size of the meal, what the meal consists of, what you have been eating before, your physical activity, your age and how your body reacts to insulin all influence the thermic effect of food. But in spite of some people’s claims, there is no evidence that grapefruit has a greater ability to change this thermic effect than other foods do. In careful, randomized studies of body chemistries, naringin, thought to be the key component of grapefruit as a weight-loss supplement, is shown not to change energy expenditure. Furthermore, a study of 352 overweight men and women found that the ‘grapefruit pill’ was ineffective in helping people slim down.
If you do decide that you want to start eating more grapefruit, despite the mixed evidence supporting grapefruit as a magic weight-loss tool, you may need to think carefully about any other medications you are taking. Grapefruit has been shown to interact with common drugs, hindering their breakdown by the body and leading to toxicity or bad side effects. Statins for high cholesterol, medicines that prevent heart arrhythmias, medicines that suppress the immune system and calcium-channel blockers can all interact with grapefruit, leading to potentially harmful side effects, so ask your doctor before you add grapefruit to your diet.