Does HRT Cause Weight Gain in Women?
No, hormone replacement therapy does not cause weight gain beyond what naturally occurs during menopause. Multiple high-quality studies demonstrate that HRT users either maintain weight or gain slightly less weight than non-users during the menopausal transition.
Evidence from Systematic Reviews and Clinical Trials
The most comprehensive evidence comes from a Cochrane systematic review of 22 randomized controlled trials, which found:
- Unopposed estrogen showed no statistically significant difference in weight gain compared to non-HRT users (0.66 kg, 95% CI -0.62 to 1.93) 1
- Combined estrogen/progestogen therapy showed no significant difference in weight gain compared to non-HRT users (-0.47 kg, 95% CI -1.63 to 0.69) 1
- No significant difference in BMI increase between estrogen/progestogen users and non-HRT users (-0.50,95% CI -1.06,0.06) 1
The Danish Osteoporosis Prevention Study, a 5-year randomized controlled trial of 2,016 early postmenopausal women, demonstrated that women randomized to HRT gained less weight (1.94 kg) than women randomized to no HRT (2.57 kg, p = 0.046) 2. This smaller weight gain was almost entirely due to a lesser gain in fat mass 2.
Understanding Weight Changes at Menopause
The menopause itself causes weight gain through decreased resting metabolic rate, not HRT 3. Weight gain is greatest in the perimenopausal years regardless of hormone use 3. The main determinant of weight gain during this period is a decline in physical fitness, not hormone therapy 2.
Body Composition Effects
HRT appears to favorably affect body composition:
- HRT prevents the increase in fat mass that typically occurs after menopause 2
- HRT may prevent redistribution of fat to a more central (android) pattern with increased waist-to-hip ratio 3
- Fat gain protects against bone loss in untreated women but not in HRT-treated women, suggesting HRT dissociates fat mass from bone mass 2
Specific Formulation Considerations
Drospirenone-containing HRT may actually promote weight loss due to its antialdosterone activity, which reduces estrogen-related sodium and water retention 4. Pooled data from two placebo-controlled trials showed statistically significant weight loss of -1.5 kg at 6 and 12 months in women receiving estradiol/drospirenone versus placebo (p < 0.001) 4.
Standard HRT regimens like continuous 17β-estradiol 2 mg/day combined with sequential dydrogesterone may help prevent increases in body fat mass and fat redistribution 3.
Clinical Implications
Fear of weight gain is one of the main factors contributing to poor HRT compliance, yet this fear is not supported by evidence 3. Women should be counseled that:
- HRT does not cause additional weight gain beyond normal menopausal changes 1, 5
- Some HRT regimens may actually help maintain or reduce weight 4, 2
- Weight gain during menopause is primarily related to decreased metabolic rate and reduced physical activity 2, 3
Common Pitfalls to Avoid
- Do not attribute normal menopausal weight gain to HRT when counseling patients, as this perpetuates an unfounded concern that reduces compliance 3
- Do not assume all HRT formulations have identical effects on weight—drospirenone-containing preparations may offer specific advantages for weight management 4
- Do not ignore the role of lifestyle factors, particularly declining physical fitness, which is the strongest predictor of weight gain during menopause 2