【On the Rise Among Young Women】What Matters Most in a PCOS Diet? Why PMS and PCOS Are Increasing, How to Eat for Balance, and Fasting Precautions

“My mood crashes before my period.” “My cycles have been irregular for a while, and trying to get pregnant isn’t working.” “I was diagnosed with PCOS and have been taking medication, but nothing is getting better at the root.” The number of young women struggling with worries like these is rising rapidly.

In fact, recent research has revealed that the sharp rise in PMS (premenstrual syndrome) and PCOS (polycystic ovary syndrome) is closely linked to “all-day grazing” (the habit of eating all day long) and modern eating habits.

Your hormone balance responds surprisingly sensitively to “what, when, and how you eat.”

So what exactly is going on between your daily meals and your hormones?

In this article, I’ll explain the science behind how eating habits make PMS and PCOS worse, and how fasting and better eating can help balance your hormones.

I’ll also cover the basic principles of a PCOS diet, a sample day of meals, and precautions to take when fasting.

What Are PCOS and PMS? The Real Reasons They’re Rising Among Young Women

PMS (premenstrual syndrome) is the general term for physical and emotional symptoms that appear 3 to 10 days before a period, and in Japan, about 70 to 80% of women who menstruate are said to experience some PMS symptoms.

A growing number of women are also developing PMDD (premenstrual dysphoric disorder), a severe form.

PCOS (polycystic ovary syndrome) is a hormonal disorder characterized by irregular periods, ovulation problems, and excess male hormones. It affects about 10 to 15% of women of reproductive age and is one of the leading causes of infertility.

In recent years, its increase among women in their 20s and 30s has become a concern.

PCOS Is Like “Eggs Stuck in a Traffic Jam Before They Can Fully Mature”

Normally, each month several follicles (sacs containing eggs) begin to grow in the ovaries, and one of them grows large and is released at ovulation.

With PCOS, however, the follicles only grow partway, and lots of small follicles build up inside the ovary.

Picture cars jammed up at a highway tollbooth, with none of them able to reach the exit.

It can happen regardless of body type, and PCOS in slim women isn’t unusual either, so don’t assume “I’m not overweight, so it can’t be that.”

PMS and PCOS are different conditions, but they have in common that hormonal imbalance is involved in both.

The “High-Insulin State” Behind the Surge

Behind this surge is thought to be a chronically high-insulin state caused by eating too many refined carbs and processed foods, and by all-day grazing (the habit of eating many times a day).

Insulin resistance is the fundamental metabolic abnormality in PCOS and is also deeply involved in PMS becoming more severe.

Think of insulin resistance as a state in which insulin, which lowers blood sugar, stops working well, so your body keeps releasing more and more of it.

When too much insulin persists, the hormonal communication network throughout your body, including the ovaries, fat, gut, and brain, gradually falls into disorder.

A lifestyle of sugary snacks and sweet drinks all day long is like blasting a nonstop, full-volume broadcast over this network.

If irregular periods continue for 3 months or more, or menstrual pain or low mood is interfering with your daily life, first get a diagnosis from a gynecologist.

4 Ways All-Day Grazing and Eating Habits Make PMS and PCOS Worse

From here, let’s break down into four parts how your daily eating patterns throw your hormone balance off.

① High Insulin → Excess Androgens → Worsening PCOS

Constantly eating refined carbs leads to a chronically high-insulin state.

High insulin acts on the ovaries and stimulates the production of androgens (male hormones).

Research has shown that many women with PCOS have insulin resistance, and blood sugar and insulin spikes after meals worsen PCOS symptoms (excess hair growth, acne, ovulation problems).

In other words, for the ovaries, insulin also acts like an accelerator pedal that says, “Make male hormones.”

② A Disrupted Gut Environment → Abnormal Estrogen Metabolism

Your gut contains a group of bacteria called the “estrobolome,” which is involved in metabolizing estrogen.

When constantly eating processed foods and sugar disrupts your gut flora, estrogen metabolism and elimination are impaired, creating a state of excess estrogen (estrogen dominance).

This is one of the factors that intensify PMS mood symptoms, breast pain, swelling, and more.

Picture the “garbage truck” that hauls away used hormones breaking down in your gut, so hormones overflow inside your body.

③ Chronic Inflammation → More Prostaglandins → Worse Menstrual Pain

Chronic inflammation from overeating and processed foods increases the production of prostaglandins (inflammatory substances).

Prostaglandins cause the uterus to contract and are the main substances behind menstrual pain and dysmenorrhea.

There are reports that the longer you keep eating an inflammatory diet, the worse your menstrual pain becomes.

④ Excess Cortisol → Not Enough Progesterone

Repeated blood sugar spikes and crashes lead to excess release of cortisol (the stress hormone).

Cortisol and progesterone (the luteal hormone) are both made from the same raw material, cholesterol, so when cortisol is prioritized, progesterone runs short.

Low progesterone is one of the direct causes of PMS emotional symptoms (anxiety, depression, irritability).

It may be easier to understand if you think of two factories competing for the same materials, with the stress-response factory always getting priority.

What all four pathways have in common is that they start from “blood sugar swings” and “digestion with no time to rest.”

Approaches to Improving PMS and PCOS With Fasting and Better Eating

Here I’ll explain how fasting and better eating work on insulin resistance, chronic inflammation, and disrupted gut flora, the root causes of PMS and PCOS.

The Positive Effects of Fasting on Hormone Balance

A review published in 2023 showed that intermittent fasting (IF) may be effective in improving insulin sensitivity, hormone profiles, and menstrual regularity in women with PCOS.

Keep in mind that there are still only a few studies in this area, and which fasting method works best varies from person to person.

When you create time without food, your foot comes off the “accelerator” of insulin, making it easier for your ovaries to settle down.

Precautions for Fasting If You Have PCOS

On the other hand, women’s hormones are very sensitive to signals that “there isn’t enough nutrition.”

If you make your fasting window too long or cut your daily food intake drastically, your body may decide “now is not a good time for pregnancy” and stop ovulating.

I explain how women can decide on their fasting window in detail in “【A Must-Read for Women】Should Women Start 16-Hour Fasting with 12 Hours? The Right Way to Fast in Sync with Hormone Balance and Your Menstrual Cycle.”

The Basics of a PCOS Diet: Eating to Keep Blood Sugar Steady, and a Sample Menu

The most important thing in a PCOS diet is to “raise your blood sugar gently and avoid releasing too much insulin.”

Rather than hunting for special foods, changing how you choose your daily staples and the order you eat in is more effective.

Choose Low-GI Staples

GI (glycemic index) is a number that shows how easily a food raises your blood sugar after you eat it.

White rice, white bread, and udon noodles raise blood sugar easily, while brown rice, multigrain rice, whole wheat bread, and soba (buckwheat noodles) raise it relatively gently.

A study published in Australia in 2010 compared 96 overweight women with PCOS who were split into a low-GI diet group and a standard healthy diet group.

Among those who completed the study, it was reported that insulin sensitivity improved more in the low-GI diet group.

However, about half of both groups (49%) dropped out partway, showing that “how easy it is to stick with” is also a major challenge.

Rather than forcing yourself to cut out staples, I recommend starting with something easy to keep up, like switching half of your white rice to brown rice.

Eat in This Order: “Vegetables → Protein → Staples”

Even with the same meal, eating vegetables, mushrooms, and seaweed first lets the fiber act as a cushion, making it easier to prevent a sharp blood sugar spike.

Next, have protein such as meat, fish, eggs, or soy, and try to eat your staple food last.

Extreme carb restriction that cuts out staples completely tends to lead to rebound binge eating and stress, and it also puts a strain on your hormones.

Thinking of it as “choosing better” rather than “cutting back” makes it easier to keep going over the long term.

Chewing well and eating slowly is another important tip for preventing blood sugar spikes.

A Sample Day of Meals for People With PCOS

Just stopping the “grazing” habit of constantly sipping sweet drinks and nibbling on sweet pastries greatly increases the time your insulin gets to rest.

Foods That Help PMS and PCOS, and Eating Habits to Avoid

Once you’ve got the basics of staples and how to eat down, let’s look at foods that support hormone balance and eating habits you’ll want to cut back on.

Foods to Actively Include

These are all things you can find at an ordinary supermarket, so start by adding one to each meal.

Small tweaks are enough, like adding chia seeds to your morning yogurt or serving grilled fish and broccoli at dinner.

Eating Habits to Cut Back On

If you think “I have to quit all of these,” you won’t keep it up, so the realistic approach is to start by cutting back on just the one habit you do most often.

Late-night meals and lack of sleep also disrupt your blood sugar and stress hormones, so pay as much attention to them as you do to your diet.

I also cover how to eat before your period in “【For Those Who Struggle Before Their Period】Can Fasting Ease PMS? Eating Rules for Hormone Balance and How to Fast Through Each Phase of Your Cycle.”

FAQ: The PCOS Diet, PMS, and Eating Habits

Here are some questions readers often ask.

Change Your Eating Habits to Improve PMS and PCOS at the Root

To balance your hormones, an approach that covers your whole lifestyle, in addition to diet and fasting, is effective.

Eating in sync with your menstrual cycle (cyclical dieting) is also effective: focusing on more iron and protein from after your period through ovulation, and on magnesium, B6, and healthy fats from after ovulation until your period, makes symptoms easier to ease.

For the basics of how to start fasting, see “【The Complete Beginner’s Guide】What Is Intermittent Fasting? Types, Benefits, How to Do It, and Why You Might Not Be Losing Weight, Explained Simply.”

Exercise helps your muscles take in sugar from your blood, making it a powerful ally in helping insulin work better.

Even just walking lightly for 10 to 15 minutes after a meal can help curb a sharp blood sugar spike.

Keeping a simple record of your cycle, weight, and mood makes it easier to notice changes after you adjust your diet, and it’s also useful when you see your doctor.

Even if you’d given up, thinking “PMS and PCOS can only be managed with medication,” changing your eating habits may bring major improvements.

Start by cutting back on refined carbs and bringing fasting and an anti-inflammatory diet into your life.

If your symptoms are severe, always proceed while consulting a gynecologist or OB-GYN.

For a science-based fasting program that supports hormone balance, also check out ufeelgreat: a program to help balance your hormones.

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