You're sleeping. You're eating the way you were told to eat. You've cut the carbs, pushed breakfast later and later, and your labs come back normal every single time.
And you still know something is off.
You're hungry again an hour after you ate. Or you're never hungry in the morning at all. And every time you ask, you're told it's just menopause.
Tell me if you've heard this before.
I've spent twenty years in hormone and longevity medicine, and here's what I keep coming back to. Most of what supports your hormones comes down to the foundations. Light. Darkness. When you eat. And so many of them cost you nothing.
That's why I wanted you to hear from Sarah Kleiner, creator of My Circadian App and board-certified in applied quantum biology. She joined me on The Girlfriend Doctor podcast to talk about leptin resistance in menopause, why so few doctors test for it, and how light and timing shape the signal.
In this post
Key Timestamps
- 00:00 - Why the foundations matter more than hacks and peptides
- 04:02 - Sarah's path from corporate America to circadian biology
- 07:22 - Two IVF rounds and a wall with conventional care
- 10:04 - What a morning circadian reset looks like
- 22:09 - Yellow, orange, or red? Choosing blue light blockers
- 24:48 - What leptin is and why Sarah calls it a master hormone
- 28:10 - Sarah's own low leptin, and the doctor who dismissed it
- 29:42 - Early signs your leptin signaling is off
- 39:31 - Why "calories in, calories out" misses timing
-
42:48 - The underrated habit of working in the shade
The leptin test her doctor called "dumb"
Sarah was in her forties and going through a hard stretch with conventional fertility care.
Nothing she was being offered explained what was going on in her body. So she asked her fertility doctor to test her leptin.
The doctor told her that was dumb. An insignificant hormone. Not worth checking.
She tested it anyway. Her leptin came back very low, even though she was carrying extra weight at the time.
That one result changed how Sarah thought about her body. It's also the foundation of everything she teaches today.
What stayed with me is the question she refused to stop asking. Why?
What leptin does while you sleep
Leptin is a hormone made by your fat tissue. Sarah calls it a master hormone, right up there with cortisol and melatonin.
She describes it as your body's accountant.
At night, leptin reports to your brain how much stored energy you have. Your thyroid, your sex hormones, and your metabolism all take their cues from that report.
In Sarah's view, that nightly conversation depends on darkness and sleep. Blue light at night, eating close to bed, and staying up late can all get in the way.
And here's the part I love. When that conversation breaks down, your body isn't attacking you. It's following the instructions it was given.
Which means you can give it better ones.
Why leptin resistance gets overlooked
Most of us have heard about insulin resistance. Leptin resistance gets far less attention, and it rarely makes it onto a standard lab panel.
In Sarah's experience, women often show signs of leptin resistance well before insulin resistance ever appears on their labs.
If you're in perimenopause or menopause and nothing on your labs explains how you feel, leptin is worth asking your doctor about.
For testing, Sarah recommends a fasted morning blood draw, 12 to 14 hours after your last meal. In her experience, eating beforehand skews the result, and so does fasting too long. Your doctor can help you interpret the number.
Early signs your leptin signaling is off
Sarah says the earliest signal she looks for is hunger that doesn't make sense. That can look like any of these.
You're hungry again soon after you eat.
You never feel satisfied.
You have no appetite in the morning at all.
That last one was Sarah. After about ten years of intermittent fasting and pushing her first meal as late as possible, she felt nauseous at the thought of breakfast.
If intermittent fasting in menopause has left you with no hunger cues at all, pay attention to that. Your body is telling you something.
How light tells your hormones what time it is
Sarah calls leptin a light-signaled hormone. In her view, it depends on sunlight in the morning and darkness at night.
In the morning. Go outside within minutes of waking, before your phone and before the overhead lights. Sarah brings water and minerals out with her, walks barefoot, and usually has her little one in tow. It doesn't have to be perfect.
After sunset. Keep your home dim. Sarah's house glows red at night, and she aims to keep light below 10 lux in the three hours before bed. Her app has a lux meter so you can check your own space.
With blue light glasses. Sarah uses yellow lenses during the day at screens or under office lighting. After sunset, she switches to orange or red to support her body's natural melatonin signal.
All day long. Put an incandescent bulb on your desk, sit near a window, and take your work outside when you can. Sarah says even the shade counts, because it still gives you natural infrared light.
Why when you eat matters as much as what you eat
The myth Sarah most wants to bust is that calories are calories and timing makes no difference.
As Sarah explains it, your body handles the same meal differently at 8 AM than at 8 PM. She also points out that eating close to bed works against your body's natural daily rhythm.
That's why I encourage women to break their fast by 10 AM. If something has to go, I'd rather you skip a late dinner than skip breakfast.
Sarah also talks about bringing healthy carbohydrates back, like resistant starches, not donuts and bagels. So many of the women she works with are coming off years of keto or carnivore, and they're scared to eat a sweet potato.
I hear that fear all the time too. It's one of the reasons I wrote MenuPause. It gives you five six-day meal plans to rotate: Carb Up, Autoimmune Paleo, Keto-Green, Carnivore, and Vegan, so you can change up your eating pattern with a plan instead of guessing. Not sure where to start? Take the MenuPause quiz.
Where to start tomorrow morning
Sarah's best advice is not to overcomplicate this. You don't need to replace every light bulb in your house this weekend.
Start here.
Step outside within minutes of waking, before you look at your phone.
Eat your first meal by 10 AM, and make sure it has protein.
Put an incandescent bulb on your desk and sit near a window.
After sunset, dim the lights and switch to orange or red.
As Sarah puts it, "consistency over perfection every single day of the week."
Small shifts, done every day, give your body clearer signals to work with. And the best years of your life are not behind you, Gorgeous. They're waiting for you.
Listen to the full episode
There's so much more in the full conversation, including Sarah's personal story, quantum biology, and how My Circadian App works. If a woman you love keeps saying "my labs are normal, but I don't feel like me," send her this episode. And subscribe on YouTube so you don't miss the shorts.
YouTube | Spotify | Apple Podcasts
Frequently asked questions
What is leptin?
Leptin is a hormone made by your fat tissue that helps tell your brain how much stored energy you have. Leptin resistance is the term used when the brain stops responding well to that signal.
Is leptin connected to perimenopause and menopause?
Leptin communicates with your thyroid and your sex hormones, which is why Sarah pays close attention to it. Most of the women who come to her programs are in perimenopause and menopause. If your labs are normal and you still feel off, ask your doctor whether testing leptin makes sense for you.
How is leptin tested?
Sarah recommends a fasted blood test in the morning, 12 to 14 hours after your last meal. Talk with your doctor about ordering the test and interpreting the results.
What color blue light glasses does Sarah recommend?
Sarah uses yellow lenses during the day for screens and overhead lights. After sunset, she switches to orange or red to support her body's natural melatonin signal.
Is intermittent fasting a good idea in menopause?
It depends on the woman. Sarah fasted for about ten years and ended up with no morning hunger signals at all. I encourage women to break their fast by 10 AM and rotate their eating patterns instead of doing the same thing forever.
Resources Mentioned
- Leptin Master Plan
- 21 Day Leptin Reset
- Free ebooks
MenuPause, my book of rotating six-day meal plans, including Carb Up, Autoimmune Paleo, Keto-Green, Carnivore, and Vegan options
Connect With Sarah Kleiner:
Connect with Dr. Anna:
Disclaimer
While I am a doctor, I am not your doctor. This post reflects Sarah's personal experience and perspective, and every woman's body is different. This is education, not medical advice, so please talk with your own physician before making changes to your health routine.
