The effect of grapefruit is attributed to the narinigerin-containing ingredient found in lemon. Naryngerin appears to act against fat accumulation and also to regulate insulin levels in the blood. A US study of obese individuals found that those who ate half a grapefruit before each meal (one and a half fruits a day in total) had lost an average of two pounds after 12 weeks. Of course, before resorting to excessive consumption of grapefruit or if you are taking medicines, it is advisable to consult your doctor.

• Eat more lemons and grapefruits by adding them to your juices