What's the connection between hormones and weight? A doctor breaks it down for women

Dr. Jennifer Ashton is a board-certified OBGYN and obesity medicine specialist who has worked with thousands of female patients over her decades-long career.

Ashton, also ABC News chief medical correspondent, said she had a "lightbulb moment" 10 years ago when she was working one-on-one with a patient.

"In fact, I had the lightbulb moment," Ashton told " Good Morning America." "It was at that time that I realized that pretty much every significant hormonal stage in a woman's life is associated with metabolic, or weight, changes."

The realization pushed Ashton to go back to school to earn a degree in nutrition and become board-certified in obesity medicine.

It also transformed the way she practices medicine, she said, explaining that it taught her that patients struggling with their weight weren't just eating too much or the wrong types of foods.

Ashton said she likes to talk about the connection between hormones and weight in order to normalize weight changes women see naturally throughout their lives.

"For a woman's reproductive life, her entire life, actually, every single major hormonal stage is often-slash-almost always associated with changes in metabolism, cravings and actually bodyweight," Ashton said, noting that the hormonal stages for women include puberty, peripregnancy, peripartum, perimenopause and menopause.

"The first thing that I like to remind people of is recognize, appreciate, acknowledge and normalize these changes. That is your body doing what it is supposed to do," Ashton continued. "The key is, how can you help it and how can you strategize your way through these normal and important hormonal milestones so that you come out feeling good about the way that you look and feel and, more importantly, that you come out of them healthy."

While women may notice weight fluctuations as they go through life changes like puberty and menopause, unfortunately for women, there is still little medical research in the field, according to Ashton.

"That's where it gets a little frustrating," Ashton said. "A lot of what we know is based on observation and association, and then safe trial-and-error, which I encourage women to do."

Ashton wrote about the connection between women's hormonal changes and their weight in her new magazine, " Better With Dr. Jen Ashton," which is available now online and in newsstands across the country.

Ashton said she wants women to understand what their body is going through hormonally at each stage, so they can work appropriately to support those changes and not get frustrated.

"If you've just had a baby, or you're thinking of becoming pregnant, or you know someone who is about to go through puberty or going through puberty, or if you or someone you know is perimenopausal or menopausal, that's not a separate issue to your weight, to your metabolism, to the way you eat," Ashton said. "Connecting the dots on those two is really going to help people get through these periods of time without kind of feeling like they're a dog chasing its tail."

Here are Ashton's three tips to help women navigate hormonal changes in their lives.

1. Be observant of changes to your body, appetite and cravings.

Ashton said to pay attention to any changes in your appetite, your cravings for certain foods and your weight, and to see if those correspond to different stages in life, like certain times of a menstrual cycle or perimenopause, the time when ovaries gradually begin to make less estrogen.

"At this time, weight gain is incredibly common," Ashton said of perimenopause, which usually hits women in their 40s. "Typically, it's midsection, midtorso weight gain that occurs despite a woman not changing what she's eating or how she's moving."

2. Use trial and error to see what works.

"If you've noticed a change in your weight or your appetite, I recommend that you can try things, but give them one to two weeks at minimum to see how do you feel in terms of your energy level, your hunger, your satiety, and then your weight," Ashton said, noting that the number on a scale is just one measure.

Ashton said another part of trial and error is testing whether certain foods make your symptoms better or worse. For example, she said that science shows carbohydrates help women during their menstrual cycle, but not all carbs are created equal.

"Just be aware there are carbs that are probably better for those cravings than others when it comes to retaining water and gaining weight," Ashton said. "And also remember that some carbs ... tend to be calorie-rich, nutrient-poor, so proceed with caution when reaching for that, especially if it's to address a craving."

3. Know that no specific food is 'right' or 'wrong.'

"There is no conclusive, good peer-reviewed nutritional science or medical science data that suggests or confirms that if you eat one thing, you will have a definite hormonal effect on the other side of the equation," Ashton said of the medical research to date.

Ashton said the lack of data points women back to the trial-and-error method to see what works for them.

She pointed out as an example, that some research has shown that a plant-based diet can have a "plethora of benefits" for women in perimenopause and menopause. With that information, women can decide the risk versus benefit of trying for themselves.

"You always have to ask yourself risk versus benefit," Ashton said. "What is the downside of eating, let's say for example, a largely plant-based, low-processed food diet. Really, no downside. Is there a potential upside on getting you through these major hormonal stages in life, absolutely."