Recommended body weight
for optimal fertility health - calculate body mass index

By achieving your recommended body weight you can significantly increase your chances of conception (this goes for men and women)! Calculate body mass index with our chart to determine if you are in a healthy weight range based on your height.

recommended body weight bathroom scales Most people are unaware of how weight issues can contribute towards infertility!

Numerous research has concluded that body fat plays a vital role within the human reproductive system. We need to be as close as possible to our recommended body weight to regulate sperm production or ovulation.

Let's try to explain why. Did you know that both men and women have families of hormones called androgens (known as male) and estrogens (known as female) within their bodies. Different ratios of these hormones are required for each gender, and they are used very differently! Hormones are chemical messengers that transfer information around the body. Body fat converts androgens to estrogens by help from an enzyme called aromatase. This is a normal body function, but excess fat (or the lack of) can interfere with the amounts of these hormones that are required for our fertility.

This whole process begins within the brain, which is ultimately responsible for the correct signals to secrete our reproductive hormones. Recent research has discovered that the brain interprets when the body is at a healthy state (our recommended body weight) for reproduction. This is due to the long chain of signals that run between our fat cells and brain.

Of the couples who are experiencing infertility, the cause for an estimated 12 percent or more is weight related (either an excess or a deficiency in body fat)! The body weight of both partners needs to be considered.

Research has confirmed that 70% of women with weight related infertility will conceive naturally once they have corrected their weight issues (either losing or gaining weight)!

Overweight or obese

The rates of obesity have risen dramatically in recent years, with our hectic lifestyles and the easy convenience of fast foods. The food manufacturing businesses are out to make money, and unfortunately we are conned into purchasing these items full of additives, preservatives and extra fat (with next to no nutritional value)!

It's too easy to exceed our recommended body weight! Mother nature has made it so that the human body can easily store fat, for use in times of famine. In today's society we don't really need that old storage capacity!

Most people are aware of the health complications that can arise from being overweight such as coronary disease and diabetes (which in themselves can contribute to fertility problems)! Fat cells also produce inflammatory hormones that can also interfere with the normal functioning of other metabolic pathways.

As estrogen is produced by our fat cells, the more weight a person carries, the higher their risk is of developing estrogen dominance diseases.

Men - Excess body fat

Here are some good reasons why men should calculate their body mass index and try to be close to their recommended body weight! When a man is overweight he will produce less testosterone, which is absolutely essential for normal sperm production capabilities. Fat cells synthesize the aromatase enzyme which convert androgens (the major being testosterone) into estrogens. When their is too much fat, more of the female hormone is produced and an imbalance is the outcome.

This results in a significant drop in sperm count and quality and a decrease in the volume of seminal fluid produced. Erectile dysfunction can also become a real problem with the reduction in testosterone.

If a man is obese, the excess skin folds around the genital area can contribute towards overheating of the testicles (sperm are susceptible to heat and can die). For a larger man, finding a suitable intercourse position may also prove difficult.

Obese men can develop a condition called gynecomastia which is an enlargement of the breasts due to the excess estrogen.

Research was conducted by William Roudebush and colleagues at the Reproductive Biology Associates in Atlanta Georgia U.S. The study was to examine the impact of male body weight on sperm cells and the DNA structure (genetic blueprint) within. Semen samples were collected from normal healthy men, age ranging from 26-45 years of age.

The researchers found that as the body mass index of the men went up, so did the rates of DNA fragmentation, and there was a dramatic drop in sperm quality. This is associated with lower fertility levels, and also a higher risk of miscarriage when a pregnancy is achieved.

The rates of DNA fragmentation rose as the BMI’s passed 25 (classed as overweight) and this became acute with BMI’s of over 30 (obese). These findings were published in the Journal of Andrology - May/June 2006, volume 27, no. 3, pages 450-452.

Research - A Danish study collected data from 1,558 men with an average age of 19, undergoing military health/fitness exams. These results were published in the journal Fertility and Sterility - October 2004, volume 82, pages 863-870. The study found that overweight men (BMI over 25) had a 21.6% and 23.9% reduction in sperm count and sperm concentration respectively than men who were in their recommended body weight range.

*Caution - Don't use any diet drugs while you are trying to impregnate your partner. Any unnecessary drugs or medications should be avoided during the preconception phase as sperm cells can be adversely affected.

Women - Excess body fat

A woman's body is made to store more body fat than men. This is for the reason of childbearing and breastfeeding. This explains why woman on average don't burn fat at the same rate as men, as a lot of women complain about (unfortunately this is mother natures way)!

However if a women develops too much body fat there will be considerably more estrogen produced in her body than is required. This can interfere with the ovulation cycle (similar to being on birth control pills). Good reason to be in your recommended body weight range!

Research has concluded that overweight women have a higher prevalence of polycystic ovary syndrome and luteal phase defect, which are major causes of infertility for women.

(PCOS) may result from the extra weight (or the other way around) as scientists do not fully understand the connection. This condition causes ovulation disorders and produces cysts on the ovaries, as well as other hormonal problems. The rate of miscarriage with (PCOS) is considerably higher than with women who do not have this condition.

Luteal phase defect (latter part of menstrual cycle) is another complication possible from carrying excess weight. This condition occurs when the body does not produce enough of the hormone progesterone, resulting in an interference of the development of the endometrium (lining of the uterus). Miscarriage can occur with this condition.

Blood flow and circulation can also become affected by being overweight, interfering with a woman’s cycle. Weight loss can increase the blood flow, therefore helping release the egg from the ovaries. This can also help with implantation of a fertilized egg in the uterus.

Statistics show that overweight women undergoing IVF treatments or embryo transfer have a lower success rate than women who are within their recommended body weight range.

Very large women may also have trouble finding a suitable intercourse position.

Although it may be a long slow road to reach your recommended body weight, there's good news. Experts suggest that if overweight or obese women try to lose 10-20% of their body weight, this will help significantly by increasing their chances of ovulation. In some cases just a 5% reduction has done the trick!

*Caution - Don't use diet drugs (or any other unnecessary drugs/medications) during your preconception phase or during pregnancy.

Risks of carrying excess weight while pregnant

There are reasons why being within your recommended body weight range can help if you do become pregnant. If a woman is carrying excess weight, she may have a higher risk of certain pregnancy complications such as hypertension (high blood pressure) or gestational diabetes (high blood glucose during pregnancy). Pre-eclampsia is another risk with symptoms of abrupt hypertension, loss of blood protein, and swelling of face, hands and feet. This condition can lead to eclampsia if not treated which is life threatening for mother and unborn.

Obese women may have an increased risk of premature birth, or babies born with neural tube defects.

*Please note - While medical studies have shown that these risks are higher for overweight or obese women, this does not necessarily mean that an overweight woman is high risk or can’t have a successful pregnancy. We always advise discussion with your personal physician regarding any medical related questions or concerns you may have.

You can loose weight while trying to become pregnant, although this must be done responsibly (no extreme dieting)! Once again we advise discussing this option with your doctor first for guidance.

Avoid dieting during pregnancy! As fat cells can accumulate numerous types of toxins, once pregnant dieting can be harmful to your unborn child. This is because the body is getting rid of these toxins (usually a good thing). However, whilst pregnant these waste products can go directly into the developing baby through the mothers blood supply.

Losing weight is a real commitment

Eating a healthy balanced diet is required for weight loss, along with a sensible exercise routine. Having some initial advice from a personal trainer at a gym is helpful. They can help you reach your recommended body weight goal by designing an appropriate individual exercise plan. This may be based around your available time, work and lifestyle. Drink at least eight - 8 ounce glasses of water daily (more if hot weather or exercising). This will aid your body tremendously, flushing out toxins and re-hydrating, which is essential for our health.

Crash diets are not the solution! They don't work long term and may put your health at risk! Reaching your recommended body weight should occur slowly and consistency over time for it to be successful. This healthier lifestyle should really be a lifelong goal, so it pays to do it right. Ask for support from friends and family, or support someone you know who could do with a little enthusiasm!

Being within your recommended body weight will give your confidence a boost through looking and feeling good. You will have increased energy, and it's also best for your overall health!

Consult a qualified medical practitioner for advice and a routine check up before beginning any weight loss/exercise routines.


There are several reasons why a person may be under their recommended body weight. A few of these reasons include peer pressure (body image issues) or poor lifestyle. Several medical disorders can also contribute towards weight loss.

Fertility issues equally apply to people who are lower than their recommended body weight. Malnourishment (not receiving enough essential nutrients in the body) is one of the potential causes. This condition often develops very slowly, over months or years with no obvious symptoms (then it catches up with you) and several health complaints/illnesses can arise.

Hormone irregularities are again a real possibility. Men and woman who are too thin, often suffer from decreased sex drives because of this imbalance.

Anorexia or bulimia

Important - If the reason for the weight loss is an eating disorder (more prevalent in females) then professional help is critical. Infertility is not the only problem caused by being too thin, as other series medical conditions may develop (or even death).

Men - Lack of body fat

A severe lack of essential nutrients that are required for the production of hormones, sperm and semen, is thought to be the major cause of infertility in underweight males.

Another theory may be that whilst losing too much weight, this may release stored estrogen from the fat cells.

Research - The same Danish study mentioned above found that underweight men had a 28.1% and 36.4% reduction in sperm count and concentration respectively.

A small number of males actually find it very difficult to keep weight on! If you are underweight and are concerned seek advice from your personal physician, who can rule out any medical reasons for your condition. Your doctor may be able to help with a weight gain plan to reach your recommended body weight. You could also see a dietitian or a natural health practitioner for diet advice.

Women - Lack of body fat

You need the right amount of fat in your body for menstruation. It's only when body fat reaches its optimal level that a girl will get her very first period!

If a female is under her recommended body weight, she is at risk of disturbing her fertility cycle. With a lack of body fat, this can result in estrogen levels becoming too low. This can cause irregular periods (oligomenorrhea) or ceased ovulation (amenorrhea) as 30% of woman's estrogen is produced by the fat cells! The subconscious brain thinks there will not be enough incoming food for a growing baby. The lack of the specific nutrients required for the reproductive hormones is another cause for an imbalance to occur.

Research was conducted by a team based at the London School of Hygiene and Tropical Medicine. Their aim was to examine associations between biological, behavioral, and lifestyle risk factors towards miscarriage. The team questioned 603 women aged between 18-55 years old whose most recent pregnancy ended in 1st trimester miscarriage (under 13 weeks). They also questioned 6,116 women whose most recent pregnancy had progressed beyond 12 weeks. The results were astonishing.

Findings confirmed that women who have a low body mass index before they become pregnant were 72% more likely to suffer a miscarriage in their first 3 months of pregnancy! Wow, that's another good reason to be within your recommended body weight range! However, they also found that this risk was reduced by around 50% by taking supplements and eating fresh fruit and vegetables. These findings were published in the online edition of BJOG December 4, 2006 - An International Journal of Obstetrics and Gynecology.

Calculate body mass index (BMI)

Body mass index is defined by an persons body weight, divided by the square of their height. This method is easy to use, and is used extensively around the world as a screening tool to determine if an individual is within their recommended body weight.

This is a good reliable general estimate for categorizing weight and the associated health risks. If you are not in your considered normal weight range, then further health assessments through a physician may be required.

If you are very muscular or athletic, your measurement may show up in the overweight range, because muscle weighs more than fat! Therefore, you may want to determine your actual body fat percentage. This can be done through most gyms or some health care professionals using a method such as the caliper skin fold test.

This table is for males and females over 20 years of age and is based on World Health Organization data.

  • Underweight less than - 18.5
  • Normal weight - 18.5-25
  • Overweight - 25-30
  • Obesity - 30 or greater

Different scientific opinions have been put forward as to an indication of the optimal body mass index for reproductive age, however they all differ slightly. Some say a BMI of 21 is the best, but being close to the normal weight parameters (BMI of 18.5 - 25) are the most recommended for fertility health.

body mass index for fertility health

Please note - If you or a family member have an eating disorder, do not delay in seeking professional help!

So now you know why being within your recommended body weight is so important! If you are trying for a baby, you have the best motivation possible to reach your goal weight!

Interesting facts about adipose tissue

♦ A persons fat cells are formed during the third trimester of pregnancy, and during puberty as the sex hormones are beginning to take effect.

♦ The average woman has around 35 billion fat cells in her body or 27% of her body weight.

♦ Women's fat cells are five times larger than men's!

♦ Women have perhaps up to twice the amount of fat storing enzymes than men. Estrogen (the female hormone) also promotes body fat storage.

♦ Women may contain half of the fat releasing enzymes than men.

♦ The average man has around 26 billion fat cells or 15% of his body weight.

♦ Men on average burn 30% more calories than women during exercise or rest!

♦ When you gain weight the number of fat cells can expand by up to six times! Once they are full they can begin to multiply.

Other influencing lifestyle factors


All couples who are thinking about trying for a baby need to read this information. It takes time for sperm cells and the ovum (female egg) to mature. How you treat your body during this preconception care time ultimately affects your fertility and future offspring!


Why is nutrition important? Learn about the essential nutrients and the roles they play within the body. Achieving our recommended body weight is a lot easier when we are eating correctly! The body is depended upon the correct balance of essential nutrients to achieve homeostasis (maintaining the regulation of all body functions). Without this balance the body starts to break down, and health disorders will occur. The reproductive system is also highly influenced by our diet.


As well as being within our recommended body weight, exercise is another important contributing element towards our overall health! Adequate levels of physical activity promote important reproductive system functions. Find out more regarding the

importance of exercise! We do however have to make sure that we don't over exert ourselves. Some people go to the extreme and do way too much physical exercise (a sort of addiction). This can actually reduce fertility levels!

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