Women Hormones, Metabolism & Energy Expenditure

Have you ever wondered why you are not able to lose weight, no matter how hard you work out?

According to Dr. Christine Mermier, when it comes to the best endurance exercise performance, fuel source and use after exercise plays a crucial role for success. Certain factors regulate the contribution and usage of ATP (adenosine triphosphate) during exercise such as the length and intensity of activity, the person’s age, training status, diet, and gender. Protein contributes a minor 1–8% of the fuel needed during submaximal exercise (Isacco, Duche & Boisseau 2012). Before puberty there is no difference between males and females in the required usage. However, during adulthood, women rely more on fats than men do for the same relative exercise intensity.

Let’s find out how:

Hormones are chemical messengers released by cells through the blood that communicate with other cells throughout the body. Each cell has specialized receptor proteins that respond to specific hormone signals, and these signals trigger changes in the cell’s growth, function, or metabolism. A negative feedback loop happens when a stimulus triggers a response that causes a decrease in the stimulus.

The Major Female Hormones and their Functions

• Estrogen & progesterone

• Both derived from cholesterol, often called ovarian hormones

Metabolism

Metabolism is all the chemical reactions that sustain the life of cells and organisms. There are two categories in this process: catabolism—the breakdown of molecules to obtain energy, and anabolism—the production of compounds needed by the cells.

Carbohydrates, proteins, and fats supply a variety of materials essential for the building, supporting, and repairing of body tissues, and for the efficient functioning of the body.

Carbohydrates come in three forms: starch, sugar, and cellulose. The last is an indigestible carbohydrate known as dietary fiber that has no caloric value and is used in diet food. Together, these three are essential energy sources for humans.

Proteins are the main tissue builders for every cell in the body. They help make hemoglobin (blood protein), which carries oxygen to the blood; it forms antibodies to fight infection; and supplies nitrogen for genetic material (DNA & RNA).

Fats are concentrated sources of energy, supplying more than twice as much of it as carbohydrates and proteins. Fats make up part of the structure of cells, form a protective cushion and heat insulation around vital organs, carry fat-soluble vitamins, and supply reserve storage for energy.

Energy Regulation, Hormonal Influences and Carbohydrate Metabolism

A key role of carbohydrate metabolism in a resting mode is to keep a constant supply of glucose to the brain. Glucose is the only fuel that the brain normally uses. Neurons are cells that send bioelectric messages to one another—they always need glucose because they are in a state of metabolic activity. Even during our sleep, neurons are at work repairing and rebuilding their structural components. It needs a constant supply since neurons can not store the glucose.

The energy needs of the muscles are what primarily decide which carbohydrates (glucose and glycogen—the stored form of glucose in the liver and muscle) are needed and how quickly to use them while exercising. Blood glucose and muscle glycogen are essential for vigorous and prolonged strenuous exercise. The development of hypoglycemia (low blood glucose) and muscle glycogen depletion highly influences exhaustion during exercise.

How do Women use Glucose and Glycogen?

According to scientific findings, women have lower rates of glucose appearance and disappearance then men do. (Tarnopolsky 2008) Tarnopolsky observes that it may be due to a low activation of the sympathetic nervous system (the fight or flight response). He adds that the slightly reduced carbohydrate use in women during endurance exercise also reflects the influence of hormones on fat metabolism.

Exercise intensity determines the level of fat or carbohydrate use during exercise. During very light exercises, most energy fuel in the form of ATP is derived from fat. This happens until you reach about 65% of the VO2 maximum. (Jeukendrup) VO2 is the largest rate of oxygen consumption measured during incremental exercise. Once you reach an 80% VO2 max, oxidation will decrease, and it can reduce fat consumption in men and women. However, by continuing endurance training, the body becomes more efficient at using fat as a fuel.

Fat factors for Women

Studies show that women store a slightly higher level of intramuscular fat in small lipid droplets as opposed to larger lipid storage (compared with men). (Tarnopolsky 2008) Studies reveal that during moderately vigorous exercise that is sustainable for 90 minutes or more (approximately 55%-75% of VO2 max) there is a progressive decline in muscle glycogen use and greater reliance on fat oxidation (breakdown) for ATP synthesis. (Holloszy, Kohrt & Hansen 1998) The adaptation during endurance exercise is glycogen sparing. Most research shows that total-body lipolysis (fat breakdown) is higher in women than in men, as women have higher levels of glycerol (the backbone molecule of triglycerides) than men in sustained endurance exercise. (Tarnopolsky 200; D’Eon & Braun 2002)

How Menstrual Cycles Affect Exercise Metabolism

Estrogen and progesterone levels rise and fall during the menstrual cycle, which affect exercise performance. (Oosthuyse & Bosh 2010) However, some studies show no difference. Oosthuyse & Bosh say that estrogen alters fat, carbohydrate, and protein metabolism, improving performance while progesterone appears to act in opposition to estrogen. The researchers suggest that increases in estrogen enhance glucose appearance and use by the slow-oxidative type I muscle fibers. The high estrogen content during the luteal phase (the latter phase of the menstrual cycle or the earlier phase of the estrous cycle) augments glycogen storage, which additionally has a meaningful influence on exercise performance. Oostheyse & Bosch note that both estrogen and progesterone suppress gluconeogenesis output during exercise. Gluconeogenesis (creation of new glucose) is a metabolic pathway that results in the production of glucose from substrates such as lactate, amino acids, and odd-chain fatty acids. It is the primary mechanism the body uses to keep blood glucose levels from dropping too low during exercise bouts. This suggests that some women will need to refuel their energy (glucose) with replacement supplements after exercising.

Female Hormone Response to Resistance Training

Resistance training is essential to support musculoskeletal health. According to a review by Kaufman, et al. (2013), women who are premenopausal have lower estrogen levels, which can lead to negative effects on bone mass. (Moghadasi & Siavashpour 2013) Resistance and strength training can help increase levels of hormones associated with bone formation, especially for women of reproductive age.

How Menopause Affects Exercise Performance

The higher use of fat as a substrate in women decreases at menopause. According to Isacco, Duche & Boisseu (2012), it is attributable to a decline in plasma estrogen (and progesterone) concentrations and a drop in fat-free muscle mass. However, the researchers note that obese, postmenopausal women training at around 50% of aerobic capacity use fat more efficiently than men of similar age. The exercise-induced increase in plasma estrogen concentrations seen in premenopausal women may partially occur in obese, postmenopausal women as well.

The research suggests that training should be a combination of steady low to moderate long-duration submaximal cardiovascular endurance exercise; fast, continuous maximal steady-state training; interval training with moderate to high-intensity intervals; and total body resistance training, which improves several hormonal responses and adaptation that impressively improve musculoskeletal health.

We at Dancing Spirit provide these exercises and movements with our classes. With a 55-minute Zumba and Aquatic class you can improve cardiovascular endurance, Yoga works as body resistance training and improves several hormonal responses and musculoskeletal health!

Send us a note and sign up for our next Transformational Yoga training and or our Zumba virtual classes!

With love,

Namaste

Millie