Talking about a healthy body weight is like talking about ‘balancing one’s hormones’: it’s so generic, it bears no weight. Pun intended.
I think every one of us knows when their body feels healthy. For example, when my weight drops too much, my immune system goes into overdrive, and I immediately catch reoccurring colds and sickness.
So instead of trying to describe something that doesn’t have a number, we are all different after all, let’s look at the role of fat and how too little or too much of it might influence our journey from puberty to menopause.
Puberty
The average age for menarche (first menstrual period in a female adolescent) is 12.8 years. However, many young girls experience their first period under the age of 10. If you compare it to the mid 1800s, where the average was 16.5 years of age[1] - that’s almost a 7-year difference!
A slightly later onset can run in some families (genetics).
However, the strongest determinant of when puberty starts is the person’s nutrition and body fat mass.
Again, to understand how adipose tissue ties in to puberty we need to back track.
Yes, you guessed it right, it all starts in the brain when the hypothalamus releases GnRH (gonadotrophin-releasing hormone) via the pituitary gland and then onto the ovaries to induce a higher level of estrogen and start the development of secondary sex characteristics (wider hips in girls for example).
This rapid growth requires a tremendous amount of energy which brings us to our body’s metabolic function and to yet another hormone: leptin.
You might have heard of leptin as the hormone that sends the message to your brain: ‘I’m full’ when you eat signalling that you’re satiated.
But there is more. Leptin is a hormone secreted from fat tissue, so the more fat tissue you have, the more leptin you have. But leptin also tells your brain that there is enough body fat to sexually develop and thereby driving the puberty and the release of GnRH.
The effect is so strong that, in mice, leptin injections alone are sufficient to induce puberty.[2]
As you can imagine, the opposite effect also can happen which is a delayed puberty due to very low body fat (and insufficient leptin production).
Quick note on the above. I'm not necessarily talking of under-fuelling due to an eating disorder (although we know that these are on the rise). Sometimes it is an unintentional mismatch between the energy intake & expenditure. Let’s say a girl that does gymnastics with 2 training sessions per day, might need up to 3,000 calories per day. Good luck trying to feed her that much. Especially at this age.
However, if we are going to look into a self-imposed starvation like anorexia nervosa, in some instances puberty might not only be delayed but also physical sexual development may be hindered, even if nutrition later becomes sufficient (e.g. reduced breast development).[3]
It is important to know that earlier periods are associated with some health conditions, most notably breast cancer, endometriosis, and chronic pain conditions.
On the other hand, the older a child is when they reach puberty, the longer it takes to establish ovulatory cycles.[4]
Reproductive years, menstruation, ovulation, fertility
The negative effects of obesity on reproductive health are well known. However, it is difficult to describe the mechanism of how obesity affects the reproductive system because it is complex and multifactorial.
Most of the estrogen is being produced by the ovaries. However, we can also convert androgens (such as testosterone) into estrogen via the process of aromatisation. So, in short: the more adipose tissue, the more estrogen. This has a direct impact on GnRH (gonadotrophin-releasing hormone) and further down the line of the hypothalamic-pituitary-ovarian (HPA) axis and oocyte (egg) development.
Obesity is an important factor for:
hyperandrogenism (high levels of androgens),
hyperinsulinemia (when the amount of insulin in the blood is higher than what’s considered healthy), and
the development of polycystic ovarian syndrome (PCOS).
These are only some of the few alterations that may explain impaired ovulatory function and the reproductive health. [5]
On the other hand, very low body weight — about 10% under normal weight — interrupts many hormonal functions in the body, potentially halting ovulation – yes, you guessed it, by influencing the HPO axis.
However, any sudden weight loss will also impact the hypothalamus and the rest of the axis by signalling to the brain that we live in a time of scarcity, and this is not the time to ovulate, or, in some cases, to menstruate.
The lack of ovulation has an impact on many different systems of the body including our brain health, bone density, joints, thermoregulation, and menstrual irregularities to name a few.
The lack of menstruation for 3 months or longer is called a Hypothalamic Amenorrhea and as you guessed correctly, will have more severe consequences than anovulation. How so? There was an interesting article on the BBC that prompted this blog post, about a woman who via extreme body building not only lost her period but brought on a premature ovarian insufficiency, or maybe even perimenopause (at the time of writing this is still to be determined). [6]
Menopause
The initial phase of perimenopause is low progesterone and then highly fluctuating estrogen (estrogen excess in relation to progesterone). Ovaries are one of the main sources of estrogen production. Another is adipose (fat) tissue.
Because of the conversion of androgens to estrogens that occurs in adipose tissue, overweight and obese females have significant higher amounts of extragonadal estrogen which can exacerbate the previously mentioned estrogen excess and its symptoms.
On the other hand, being underweight can also have a detrimental effect on our health since after menopause adipose tissue is the primary source of estrogen production in post-menopause in the body. This is especially important with regards to bone density.
Being underweight might also increase other symptoms such as increased fatigue, dry or itchy skin, vaginal dryness, urinary infections, heart palpitations and vasomotor symptoms can be exacerbated.
Conclusion
Our body is a temple, and we should be looking after it as such. Any deviations from that path can have repercussions during our whole lifetime, from puberty to menopause.
My wish, as I write this, is that we women stop jumping on the bandwagon of crash diets and ways to ‘trick’ the body. But instead, to look after our body as it serves us on this journey from a girl to a woman.
Questions? Thoughts? Comment below.
[3] Why we get sick. Benjamin Bikman, PhD [4] Blood. Dr Jen Gunter
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