From the Guidelines
Estrogen alters body composition by increasing body fat, particularly in subcutaneous areas, as evidenced by a 3.0% to 5.5% reduction in lean body mass and an increase in total body fat among transfeminine people undergoing gender-affirming hormone treatment 1.
Effects of Estrogen on Body Composition
Estrogen's influence on body composition is multifaceted, involving decreases in lean body mass and increases in body fat, as reported in a systematic review by Harper et al. within the context of feminizing gender-affirming hormone treatment 1. This change in body composition is characterized by a reduction in muscle volume and quadriceps cross-sectional area, indicating a shift towards fat accumulation.
Mechanism of Fat Distribution
While the exact mechanism of how estrogen stores fat cells is complex, it is known that estrogen promotes fat storage in subcutaneous areas, such as the hips, thighs, and buttocks. This is part of estrogen's broader role in regulating fat metabolism, including enhancing insulin sensitivity and modulating enzymes involved in fat storage and breakdown.
Clinical Implications
The increase in body fat due to estrogen, as observed in transfeminine individuals undergoing hormone treatment, highlights the importance of monitoring body composition changes in the context of hormone therapy 1. Understanding these effects is crucial for managing potential metabolic health risks associated with changes in fat distribution patterns.
Key Findings
- Estrogen decreases lean body mass and increases body fat in individuals undergoing feminizing hormone treatment.
- The reduction in lean body mass ranges from 3.0% to 5.5%, with a corresponding increase in total body fat.
- Estrogen's effects on body composition are part of its role in reproductive health, influencing fat distribution and metabolism.
From the Research
Estrogen's Role in Fat Cell Storage
- Estrogen has been found to play a significant role in the regulation of fat metabolism, with studies indicating that it inhibits lipolysis in adipose tissue 2.
- The effect of estrogen on fat cell storage is thought to be mediated by the activation of estrogen receptor alpha (ER-α) in adipose tissue, which leads to a reduction in lipolysis 2.
- Research has also shown that estrogen increases the size and number of subcutaneous adipocytes and attenuates lipolysis, leading to an accumulation of fat in the hips, buttocks, and thighs in females 3.
Gender-Specific Differences in Fat Distribution
- Women tend to accumulate fat in the subcutaneous tissue, whereas men accumulate fat in the visceral tissue 3.
- After menopause, there is a redistribution of fat depots, and post-menopausal women develop increased amounts of visceral fat, which is associated with an increased risk of obesity-related diseases 3.
- Estrogen has been found to have a protective effect against obesity-related diseases, with pre-menopausal women having a lower risk of developing these diseases compared to men 3.
Molecular Mechanisms of Estrogen's Effect on Fat Cells
- Estrogen receptor alpha (ER-α) has been found to play a crucial role in the regulation of adipose tissue metabolism, with studies showing that mice lacking the ESR1 gene (which encodes ER-α) accumulate more fat 2.
- The enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) has also been found to be involved in the regulation of adipose tissue metabolism, with estrogen attenuating its activity in liver, kidney, and testis but upregulating its mRNA expression in preadipocytes from women 3.
- Estrogen has also been found to regulate adipose development and improve systemic glucose homeostasis in both males and females, with the underlying mechanism thought to involve interactions of estrogen receptor signaling events involving lipolytic and/or lipogenic enzyme activity, free fatty acid metabolism, and adipocytokine production 4.
Therapeutic Applications of Estrogen in Obesity Treatment
- Estrogen replacement therapy has been found to have a beneficial effect on adipose tissue biology and metabolism, with potential therapeutic applications in the treatment of obesity-related metabolic disorders 4.
- Selective estrogen receptor modulators have also been found to have a beneficial effect on glucose metabolism, with potential therapeutic applications in the treatment of obesity-related metabolic disorders 4.
- Estrogen and its derivatives have been found to have potential therapeutic applications in obesity treatment, with studies showing that they can regulate adipogenesis and adipose tissue activity in health and the course of obesity 5.