You can lose your period (amenorrhea) with significant weight loss, often when your Body Mass Index (BMI) drops below 18.5, but it's more about low body fat (around 22%) and energy deficiency from restricting calories or over-exercising, not just a specific number. Your brain stops signaling for ovulation when it perceives a threat to reproduction due to lack of energy, shutting down menstrual hormones.
Being underweight can cause you to not have a period. This commonly occurs in competitive athletes and women with eating disorders. Women need at least 22% body fat to menstruate regularly. 11 Having a BMI of 18.5 or under can impact your period.
Excessively low body weight — about 10% under normal weight — interrupts many hormonal functions in the body, potentially halting ovulation. Women who have an eating disorder, such as anorexia or bulimia, often stop having periods because of these abnormal hormonal changes.
Weight loss-related amenorrhea is defined as the cessation of menstrual periods for >6 months following a short-term weight loss >10–15% of the standard body mass, and mainly occurs in adolescents and women of reproductive ages (2).
Women who lose too much weight or lose weight too quickly may stop having a period, or have irregular periods. Women who have obesity may also have irregular periods. A regular period is a sign of good health. Reaching a healthy weight can help women who have irregular periods to have cycles that are more regular.
Missed or late periods
The 3-3-3 rule for weight loss is a simple, habit-based method focusing on three key areas: 3 balanced meals a day, 3 bottles (or ~1.5L) of water by 3 PM, and 3 hours of physical activity per week, aiming for consistency over complex diets. It simplifies fat loss by establishing rhythm through consistent eating, adequate hydration to support metabolism, and regular movement, promoting sustainable health without intense calorie counting or restrictive rules, says Five Diamond Fitness and Wellness, Joon Medical Wellness & Aesthetics, and EatingWell.
If amenorrhea lasts a long time, problems similar to those associated with menopause may develop. They include hot flashes, vaginal dryness, decreased bone density (osteoporosis), and an increased risk of heart and blood vessel disorders.
Weight loss occurs in 2 stages: fast weight loss, where the body sheds water, glycogen, and some muscle, followed by slow weight loss, where fat loss becomes the primary focus after glycogen stores are depleted. Weight loss includes fat, water, muscle, and glycogen, while fat loss specifically targets body fat.
Periods stop due to natural events like pregnancy, breastfeeding, and menopause, but also from lifestyle factors such as extreme weight changes, excessive exercise, and high stress, hormonal imbalances from conditions like PCOS or thyroid issues, certain medications (birth control, antidepressants), and underlying medical issues, all causing a condition called amenorrhea.
Women frequently ask their doctors, “Can anaemia stop your periods?” While anaemia does not directly stop menstruation, severe iron deficiency might make it difficult for the body to generate adequate red blood cells, causing irregular menses or even total period failure in some severe cases.
Eating disorders, especially anorexia nervosa, can impact your menstrual cycle and even cause your period to stop. When your period stops due to eating too little or exercising too much, this is a warning sign that your body is not functioning correctly, and should not be taken lightly.
Don't ignore unexpected missed periods
But if your regular menstrual cycle stops unexpectedly, there's a reason for concern. Don't let it go more than three months before you call your doctor.
Sudden weight loss can also cause your periods to stop. If your BMI falls below 18.5 for whatever reason, especially if this drop is sudden, your periods may stop completely. If you are struggling with an eating disorder, it is important to seek help.
A BMI between 18.5 and 25 kg/m² indicates a normal weight. A BMI of less than 18.5 kg/m² is considered underweight. A BMI between 25 kg/m² and 29.9 kg/m² is considered overweight. A BMI of 30 kg/m² or higher is considered obese.
If you are underweight, you may be at greater risk of certain health conditions, including malnutrition, osteoporosis, decreased muscle strength, hypothermia and lowered immunity. Underweight is also known to shorten people's lives, due to early death.
No single body part loses fat first. Everyone loses fat from different places initially, depending on a variety of factors. In general, women may lose fat from their legs first, and men may lose fat from their torsos first — but it's highly individual.
A 20 pound weight loss is noticeable for most adults. Even before the mirror reflects major visual changes, your daily life begins to feel easier and more comfortable. The body responds quickly to reduced weight, especially in the midsection. These changes help strengthen confidence and motivation.
The average weight gain during this period is approximately 1-3 pounds (0.5-1.4 kg), though can range from no noticeable change up to 5 pounds (2.3 kg) depending on the individual. Research on individuals with regular menstrual cycles found that gaining about one pound during the week before menstruation is common.
Primary amenorrhea, that is where the girl who reaches her 16th birthday has never had a period, requires a genetic, endocrinologic (hormonal) and anatomic workup. The pelvic organs are evaluated, usually with an ultrasound to make sure they are present and have developed normally.
8 Safe and Effective Ways to Induce Menstruation
The most common reasons are:
According to fitness coach Raj Ganpath, losing 10 kg in 2-3 months is possible but highly unsustainable. He explains that to achieve this, you need a daily calorie deficit of about 1,300, which is extremely difficult to maintain.
Her diet included meals like vegetable poha, fruit, roti, and grilled chicken. Alia trained with Yasmin Karachiwala, blending Pilates, cardio, and strength exercises. Her 7-day routine included running, push-ups, yoga, squats, and crunches to tone and lose weight.
While some studies have suggested that eating multiple small meals throughout the day can increase metabolism and help with weight loss, others have suggested that there is no significant difference in weight loss between those who eat three large meals versus those who eat multiple small meals.