Fad diets: a cause for concern

Health professionals in the UK are reporting a rise in the number of young women with fertility issues as a result of fad diets.

It is already known that anorexia is a risk for fertility in young women. It can take the body a long time to recover full reproductive function following treatment of the condition. However, anorexia only affects around 1% of the population.

What is less well known is that it doesn’t necessarily take a clinical eating disorder to result in similar problems for fertility. A long-term fad diet can do it too! This is why UK health professionals are seeing an unprecedented rise in the number of young women with fertility problems as a result of their mission to become skinny. These diets can cause long-term damage, making future conception difficult.

Renee McGregor, Sports Dietician specializes in hormonal function and disordered eating. She said, “A few years back I’d get a couple of referrals a month about missed or stopped periods, now it’s 40 a week!”

What’s the problem?

In two words, the problem is hypothalamic amenorrhea: known more simply as absence of periods. It affects around 1-3% of women of fertile age.

It can be caused by a number of factors, but two of the most prominent are:

  • Restrictive diets
  • Heavy exercise

Many young women on fad diets combine the two, doubling the risk. Ms. McGregor said, “You don’t have to starve for the body to be under-fuelled. Many of my patients have adopted restrictive diets they’ve seen on social media. Others are doing trendy fasting diets while following high-intensity workouts. They can go for years without noticing there’s a problem because they take contraception and have a withdrawal bleed every month. But when they come off it, the periods don’t come back.”

What does it mean in terms of trying for a baby?

Ms. McGregor explained, “Often the body needs more weight than you might think it needs, following a period of under-nourishment, to decide if it’s safe to carry a baby.” So key parameters of reproductive health such as body mass index (BMI) and sex hormone levels, oestrogen, luteinising hormone (LH) and follicle stimulating hormone (FSH) may return to normal. But still, no periods!

This is because, as Ms. McGregor explained, “A certain amount of body fat is needed, as well as enough carbohydrate. It is only when there’s enough fat and carbohydrate that signals are sent to the brain, firing up the reproductive system.”

Because women have a finite number of eggs, the longer a woman goes without periods the higher the risk of a reduction in the number of eggs available. Also, the ovaries may not be releasing enough hormones to sustain a healthy pregnancy. Yet GPs often don’t see this as being a problem because the key health parameters are all registering normal. It is only if patients are seeking IVF that they will be referred for specialist treatment.

This is an issue for many of Ms. McGregor’s patients as some of them are sometimes misdiagnosed with polycystic ovary syndrome, which can also be characterised by a lack of periods.

BMI is key

Studies demonstrate that ovulation is only possible and healthy when the body fat ratio is above about 21%. With that in mind, NHS guidance states that women, whether menstruating or not, must have a body mass index (BMI) above 19 before starting fertility treatment.

The NHS guidance is in place because if BMI drops below 18.5 the chance of pre-term hospitalisation increases by 10%. It also presents an increased risk of caesarean section, miscarriage and low body weight for the baby.

What is a healthy BMI?

Just as obesity can affect fertility success, so can the opposite condition where fashionably skinny women are verging on pushing their bodies into starvation mode just by doing an extra exercise class or two a week.

A healthy sustainable BMI for a woman trying for a baby is 20-25. It is easy to check this just by knowing your height and weight. There are many online BMI calculators you can use to get an instant result.  However, if you want to change your BMI safely it is best to always consult a healthcare professional.