Weight and Fertility

Weight is a core issue for sex hormones and fertility; a classic example of this is the menarche (a girl’s first period) has been stable to an average weight of 104.5 lbs (47.5 +/- 0.5 Kg) for the last 120 years.  However, girls now reach that weight (and the menarche) at about 12½, while it was 16½ in 1900. This dramatic four-year remodelling has physical and psychological outcomes, and the weight-hormone relationship will continue throughout her life.

In general, a healthy weight leads to optimal fertility, and fertility falls further from a normal BMI, with underweight women having the worst weight-related fertility issues, as they’re at risk of low hormone levels disrupting or stopping cycles. However, excess weight is the most common weight-related fertility problem, especially in the West:

• 35.7% of USA adults were obese in 2010 ⁱ
• Nearly a third (32%) of 20-39-year-old USA women were obese in 2011
• 86.3% of US adults are expected to be overweight in 2030
• 51.1% of US adults are expected to be obese in 2030

Somewhere between 16-18% of total US healthcare costs are expected to be obesity-related illnesses by 2030. ⁱⁱ

High BMI and health

Having a high BMI increases the risk of a range of health issues, including:

• Infertility
• Cardiovascular disease
• Hypertension
• Diabetes

The average weight has been rising since a rapid rise in childhood obesity rates in the 1970s because ⁱⁱⁱ

• More “empty calories” consumption in high-calorie foods and drinks rather than “proper meals”
• More food is eaten away from home or in convenience foods
• Children burn fewer calories in activities like walking to school
• Kids spend more time watching television and surfing the web

Female fertility and weight

Being average weight maximises a woman’s fertility, and while obesity reduces fertility, it’s not as bad as being too thin:

• Women with a BMI below 17 are 1.6x more likely to be infertile
• Underweight women are 1.3x more likely to have pre-term births
• Fertility treatment costs for “overweight non-ovulating” women are 54% higher than for “normal weight non-ovulating women”
• Obese women take longer to get pregnant than normal BMI women ^iv
• Miscarriage rates are higher for obese women ^v
• Fertility treatment costs for “obese non-ovulating women” are 100% higher than for “normal weight non-ovulating women” ^vi

Male fertility and weight

The rise in male infertility over the past 30 years has coincided with a three-fold increase in obesity in men of reproductive age. There’s evidence that obesity changes hormone levels and testicular structure, lowers sperm quality and reduces a man’s potential to have children: ^vii

• An increase in BMI by as little as three units lowers male fertility ^viii
• Obese men are 3x more likely to have low semen quality than average-weight men ^ix
• Rises in BMI reduce sperm concentration and motility ^x
• Overweight men have more damage to their sperm DNA ^xi
• Obesity promotes erectile dysfunction because a hormone (aromatase) in fat tissue converts testosterone to estrogens
• Male obesity affects the metabolic and reproductive health of their children, with evidence that paternal health cues pass to the next generation ^xii

Childhood outcomes

Weight issues tend to run in families, and overweight parents increase the chances that their adult children will have:

• Type II diabetes ^xiii
• Obesity
• High cholesterol
• Hypertension ^xiv
• Stroke
• Heart attack ^xv
• Asthma
• Autism

Changing weight

Somewhat surprisingly, both under- and over-weight people face similar issues:

1. Their digestion is failing to nourish and support the body, which can encourage body fluids to accumulate.
2. Their microbiomes are unbalanced, weakening digestive function and disrupting nutrition and hormonal balance. Unappealing but true, faecal transplants of healthy microbiomes successfully treat both underweight and overweight conditions. ^xvi–xvii
3. Poor diet choices fundamentally affect microbiome health.
4. Unhealthy emotional relationships with food are complex and difficult to manage.

Long-lasting weight change is impossible without lifestyle changes, or any weight lost or gained will revert to “what was normal” quickly, as weight changes need to be maintained for a year to become the “norm”. Achieving a healthy weight has to focus on strengthening digestion in a gradual and sustained way.

Exercise helps promote digestive function by burning calories and improving fluid and hormone balance, and we suggest it should match Personal Fertility Profile (PFP) needs. For many people, weight change is vital to raising their fertility, and when overweight or obese women:

• Lose 10% of their body weight they reduce their body fat by 30%
• Most obese women resume regular ovulation after a 10% weight loss
• Losing 10.2kg (22lb) results in 90% of obese women resuming ovulation ^xviii

Crash dieting

• Denies people their nourishment and leaves them feeling denied
• Weakens digestion
• It makes the situation worse in the long term and reduces fertility

Exercise helps to promote digestive function by burning calories and improving fluid and hormone balance, and we suggest it should match Personal Fertility Profile (PFP) needs. For many people, weight change is vital to raising their fertility, and when overweight or obese women:

• Lose 10% of their body weight they reduce their body fat by 30%
• Most obese women resume regular ovulation after a 10% weight loss
• Losing 10.2kg (22lb) results in 90% of obese women resuming ovulation ^xviii

There are simple rules on how to lose weight:

• It’s easier to succeed if you’re part of a group, so get support.
• Routine is essential, and structures that support and avoid regular decision-making are key. Having made a choice, just follow it through.
• Missing meals weakens digestion, and the diet needs to strengthen digestion, not weaken it (see Energy)
• Avoid sugar as much as possible, as it gives a short “up” and a very long “down”.
• Work on changing the emotional language around food, of being denied “treats” to focus on the multiple positive outcomes of the choices being made.
• Changing food types and portion sizes alter energy levels and the palette in surprisingly short times, and noticing this is rewarding.
• Increase whole-foods and vegetables in the diet, cook more and attempt the “30 different fruit and veg a week” challenge.