From Thyroid to Stress: 13 Hidden Reasons Behind Unexplained Weight Gain

For women, perimenopause—a transitional phase often beginning in the late 30s or 40s—can trigger weight gain. Fluctuating hormone levels, loss of muscle mass, and a natural slowdown in metabolism all contribute to a gradual increase in body fat, especially around the abdomen. Even those who maintain their usual diet and exercise routine may notice changes.