As you enter your forties, you are also entering perimenopause, when levels of your sex hormones progesterone and estrogen decline. Besides regulating your menstrual cycle and reproductive functions, these hormones also impact restful sleep and relaxation. A decrease in progesterone and estrogen levels may lead to sleep disturbances, restlessness, and insomnia.1 Because changes in sleep patterns have been associated with weight gain, sleepless nights may make weight loss increasingly difficult.2
People naturally lose muscle after 40, especially women after menopause. Because muscle burns more calories than fat, this can slow down your metabolism and make it harder to shake those stubborn pounds. Strength-training exercises -- lifting weights or doing body-weight exercises, like push-ups and squats -- at least twice a week can help you keep those muscles.