The scale can be useful to keep an eye on your weight, but since your weight fluctuates, the number on the scale is not always leading.
You have probably lost a lot of fluid, unfortunately that is not body fat.
Making body fat takes time. Before your body decides whether to convert snacks into energy or body fat, it will first have to digest them, which takes about 24 hours. After a big meal you usually weigh more, you still have all the nutrition in your body, but that does not mean that you have gained weight. That doesn't happen that quickly.
Read also: 'Why the scales can go'
As your period approaches, your weight tends to increase. The difference can be a few pounds. Exactly how it is that you are heavier just before your period is not one hundred percent scientifically explained. The peak of the female sex hormone estrogen probably plays a role during the latter part of your cycle.
Researchers have found that a (structurally) increased estrogen level in the body causes the body to store extra fat, especially around the waist, thighs, buttocks and upper arms. Also, high estrogen levels can cause your body to retain more water. Chances are you will see this reflected on the scale. The good news:the pounds will disappear on their own once you have your period. Because then your estrogen level drops again.