Since the woman's body bloats as it retains water, it is the reason why it is hard to lose weight during a period. Not to say that losing weight during your period is not possible, but you will have to fully take advantage of your body's natural mechanisms. A woman is more inclined to lose weight during the third and the fourth day of her period as in the first two and this has to do with the progesterone and oestrogen levels present during a cycle.
Avoid eating processed and junk food before your period starts. These type of meals will slow your body's detoxification and contribute to the weight gain during your menstrual cycle. These include any products containing caffeine, alcohol, sugar, dairy or spices.
Eat small meals six times a day containing lots of vegetables, soy and fruits. Since soy contains isoflavones it will also help to diminish your menstrual symptoms.
Perform low intensity cardio exercise during the first two weeks of your period. These should be done during 30 to 60 minute sessions at least three times a week pushing your heart rate to 75 per cent of its maximum rate.
Start high intensity cardio exercises during the last two weeks of your menstrual cycle. These should be done within 30 minute sessions getting the heart rate to 85 per cent of its maximum rate.