Menstrual problems and obesity
BMJ Group Medical Reference
Women who have too much fat on their body may find that their monthly cycle ( menstrual cycle) is disrupted. They may stop having periods altogether.   
Fat seems to increase levels of a hormone called testosterone in the body. This may cause the menstrual problems. It can also mean you grow some coarse hair on your face.
Women with a condition called polycystic ovary syndrome tend to put on weight easily. They may also have irregular periods and grow more hair on their body or face.
Hormones are chemicals that are made in certain parts of the body. They travel through the bloodstream and have an effect on other parts of the body. For example, the female sex hormone oestrogen is made in a woman's ovaries. Oestrogen has many different effects on a woman's body. It makes the breasts grow at puberty and helps control periods. It is also needed to get pregnant.
The menstrual cycle is the regular monthly process that causes an egg to be released from the ovaries so that a woman can get pregnant. The menstrual cycle causes her period, the bleeding that happens if she does not get pregnant.
polycystic ovary syndrome
Polycystic ovary syndrome (PCOS for short) is a problem that affects a woman's ovaries. Eggs stored in your ovaries grow into small lumps called cysts. This can stop the eggs leaving the ovary and can cause infertility. Women with PCOS also have an imbalance in their hormones.
Testosterone is a sex hormone. When boys go through puberty, testosterone causes the development of male characteristics like a deep voice and a muscular body. Testosterone is also known to affect men's sex drive and mood. Although testosterone is thought of as a 'male hormone', women also make testosterone (although they make much less of it then men).
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