From the day you were conceived your body was changing, your embryonic cells multiplying by the day. Through infancy and childhood your body continued to rapidly change, a process known as growth and development, which was carefully tracked by your doctor to make sure that were on track. Not growing/developing properly would have been a sign that something was wrong – perhaps an illness, genetic condition, or perhaps something nutritionally that you weren't getting. It's so crucial to monitor these things during this phase because the body changes so rapidly.
Many people aren't aware that their body is expected to continue to change throughout adulthood. Society often places the expectation that we should be able to maintain their high school weight for the rest of our lives. This is preposterous – our bodies aren't even done developing at 18 years of age. This typically occurs in early to mid-20's.
If you are a woman, your body will change throughout your life in relation to your hormones. Biologically one of the female body's most powerful functions is childbearing. Thus, during your most fertile years you will likely experience widening of the hips, increased adipose deposits on the abdomen, hips and thighs, as these changes prepare you for the possibility of carrying a child to term.
As you approach menopause, your sex hormones start to decrease as the body is less able to handle the process of childbearing. The transition from pre- to post- menopause can take several years, and more body changes tend to occur during this time. You will likely experience a change in your body shape and notice that you carry more of your weight in your abdomen and less in your hips. You will also start to experience the natural process of sarcopenia (muscle loss) that occurs with age. This means that your metabolism will gradually slow down, as muscle is metabolically active.
What this means for women is that you are likely to experience weight gain during and after menopause. This weight gain is actually protective. Studies show that elderly women at higher weights live longer than those at lower weights. (The body sure is smart and knows exactly how to take care of itself.)
I suspect that when you reach the end of your life you will not reflect on the changes in your weight over your lifetime. Most likely you'll recall the memories created with loved ones and the valued relationships that you had. Consider how much of your time you have wasted in your younger years worrying about something that eventually won't matter. Trust your body to take care of its weight according to your life stage, and live a valued, vibrant life instead.