Do you gain weight or lose weight with Hormone Replacement Therapy (HRT)?

Weight Changes with Hormone Replacement Therapy (HRT)

HRT does not cause significant weight gain beyond what normally occurs during menopause, and some HRT regimens may actually help prevent increases in body fat mass and fat redistribution.

Effects of HRT on Weight and Body Composition

Weight Changes

• A Cochrane systematic review found no statistically significant difference in mean weight gain between those using unopposed estrogen and non-HRT users (0.66 kg, 95% CI -0.62,1.93) 1
• Similarly, no significant difference was found in mean weight gain between those using estrogen/progestogen therapy and non-HRT users (-0.47 kg, 95% CI -1.63,0.69) 1
• A retrospective study of 139 perimenopausal women found that weight gain was actually higher in the untreated group compared to the HRT group (434g vs 76g), although this difference was not statistically significant 2

Body Fat Distribution

• The menopause itself is associated with changes in body fat distribution, with an increase in central (abdominal) fat regardless of HRT use 3
• HRT may actually have beneficial effects on body fat distribution:
  • A study of postmenopausal women with BMI ≥25 kg/m² found that all three types of HRT studied caused significant decreases in waist circumference and subcutaneous abdominal fat (p<0.001) 4
  • These effects were more pronounced in women with waist circumference ≥88 cm and subcutaneous fat ≥33 cm 4

Factors That May Influence Weight Changes with HRT

Type of HRT

• No significant differences in weight effects were found between:
  • Estrogen alone vs. estrogen with progestin 2
  • Standard dose vs. low dose regimens 2
  • Different administration routes (transdermal vs. oral) 4

Pre-existing Risk Factors

• Women with higher baseline waist circumference (≥88 cm) showed more favorable changes in body composition with HRT 4
• Coronary heart disease remains a leading cause of death among women, and HRT has diverse effects on metabolic factors including lipid levels, blood pressure, coagulation factors, weight, and inflammation 5

Contrasting Evidence in Transgender Populations

• In transgender populations receiving gender-affirming hormone therapy:
  • Transmasculine individuals (assigned female at birth) showed weight increases of 2.35 kg within 2-4 months of starting testosterone therapy 6
  • Transfeminine individuals (assigned male at birth) showed stable weight for the first 21 months of estrogen therapy before beginning to increase 6
  • These findings suggest hormonal influences on weight may differ based on biological sex and hormone regimen 6

Common Concerns and Misconceptions

• Fear of weight gain is one of the main factors contributing to poor compliance with HRT 3
• Despite common beliefs, evidence suggests HRT does not cause significant weight gain beyond what normally occurs during menopause 3, 2
• The menopause itself is associated with:
  • Decreased resting metabolic rate
  • Increased body weight
  • Redistribution of fat mass with increased waist-to-hip ratio 3

Monitoring Recommendations

• Body weight and body composition should be monitored before and during HRT
• For patients with concerns about weight:
  • Reassurance that HRT itself is unlikely to cause significant weight gain
  • Lifestyle modifications including diet and exercise remain important during the menopausal transition
  • Some HRT regimens may actually help prevent increases in central fat distribution 4

Potential Side Effects of HRT to Consider

While weight gain is not a significant concern with HRT, other potential side effects should be considered:

• Increased risk of breast cancer (RH, 1.26; 95% CI, 1.00 to 1.59) 5
• Possible increased risk of coronary heart disease 5
• Increased risk of stroke 5
• Increased risk of venous thromboembolism 5

These risks should be weighed against the benefits of HRT for managing menopausal symptoms and preventing bone loss.