I am 52 years old and one year into menopause. Why is my body changing, and what happened to my energy?
Your Menopause Question: I am 52 years old and one year into menopause. Why is my body changing, and what happened to my energy?
Our Response: There is one word that now is entering the lexicon of menopause biology; energy expenditure (EE). A decline in EE leads to increased obesity (Karvonen-Gutierrez, 2016). So what does menopause have to do with EE? The answer expands our understanding of weight gain by linking our brain and our gut (Poehlaman, 1998). And the timing of those alterations highlights the impact of the menopause transition, the one to three years leading up to menopause, as the culprit (Baker, 2017).
First the brain. In early puberty, a small group of neurons in our hypothalamus called the KNDy neurons (for kisspeptin, neurokinin B, and dynorphin) are awakened (McCarthy, 2013). They, in turn, activate a cascade of events including other neurons in the hypothalamus, the pituitary, and finally the ovaries to initiate estradiol production, the most powerful of the body’s estrogens. Young girls begin to grow taller, observe early breast development, and in time, begin to menstruate. More recently, studies have shown that the gut is a player in this estradiol-driven process. The gut has a well-established neuronal system that communicates with our brain via vagus nerves (Muller, 2020). Moreover, within the gut, billions of bacteria, largely made up of four major families, are actively analyzing digested food and sending their interpretations to the brain. Any imbalance of this bacterial distribution can lead to altered digestion, impaired absorption, and inflammation (Lam 2011).
The importance of estrogen biology now enters the picture. These intestinal bacteria are kept healthy by estradiol, but they, in turn, take conjugated estradiol from the ovaries and metabolize it to free estradiol, which is its active form (Baker, 2017). But why is this important to our menopause discussion?
In the menopause transition, before menses cease completely, there is a decline in estradiol production as the ovaries age. Recall, estradiol is a powerful anti-inflammatory hormone, so one of its roles is to keep the important families of bacteria in the GUT healthy (Chen, 2016). Loss, or even just decline of estradiol, alters the balance of gut bacteria that, in turn, can disrupt normal intestinal absorption. The potential outcome is increased fat deposition, bowel inflammation, insulin resistance, and diabetic and cardiovascular risk (Poehlman, 1998, and Lam, 2011).
But wait! How about energy expenditure? Recent studies now show that signals from gut bacteria and the gut’s neural system transmit information on bowel content to the dorsal raphe nucleus in our brainstem (Schneeberger, 2019). The dorsal raphe nucleus controls thermogenesis (our body’s core heat) by regulating utilization of brown fat, our most important source of fuel. Alterations in this gut-brainstem communication results in decreased activity in order to conserve energy expenditure.
To be fair, our understanding of the biology of the KNDy neuron-brain stem-GUT-bacteria phenomenon results from studies of laboratory-based animal models. Does loss of energy expenditure apply to the clinical setting? And, is the menopause transition involved in this alteration? To address this question, Duval followed 102 perimenopausal women age 49 +/- 1.9 years for five years (Duval, 2013). They measured body composition, physical exercise, resting activity, and calorimetric measurements. Their results showed that during the menopause transition, total EE declined primarily by reduced physical activity, time of physical exercise, and increased sedentary time. More significantly, these changes were most pronounced in the menopause transition but seemed to stabilize once a woman was in menopause.
Bottom line; the menopause transition is a critical public health target. By modifying one’s diet toward plant-based nutrition, and by increasing one’s exercise, those in the menopause transition can control the biologic impact of declining estradiol and positively influence their health as they transition into menopause.
James Woods |