The Science of the Keto Diet for PCOS and Insulin Resistance; Benefits and Risks for Women Over 40

The ketogenic (keto) diet has become a popular approach for managing weight, improving blood sugar control, and supporting hormonal health. For women with polycystic ovary syndrome (PCOS) or insulin resistance, research suggests it may offer particular benefits. However, for women over 40, there are important health considerations — especially when it comes to long-term use, cholesterol levels, and nutrient balance.

How the Keto Diet Works

The keto diet is a very low-carbohydrate, high-fat diet that shifts the body into a metabolic state called ketosis. By drastically reducing carbs (typically to 20–50 grams per day), the body runs primarily on ketones — compounds made from fat — instead of glucose from carbs.

This shift in fuel use can:

• Reduce blood glucose and insulin levels

• Increase fat burning

• Alter appetite-regulating hormones, leading to reduced hunger

Why Keto May Help PCOS and Insulin Resistance

1. Improving Insulin Sensitivity

• Women with PCOS often have insulin resistance, meaning their cells don’t respond properly to insulin.

• Studies have found that keto can lower fasting insulin, reduce blood sugar spikes, and improve insulin sensitivity.

2. Supporting Hormonal Balance

• High insulin can drive excess androgen (male hormone) production in PCOS, leading to symptoms such as irregular periods, acne, and excess hair growth.

• By lowering insulin, keto may help reduce androgen levels and improve menstrual regularity.

3. Potential Weight Loss Benefits

• For some women, keto leads to significant weight loss, which can further improve insulin sensitivity and PCOS symptoms.

Health Concerns for Women Over 40

While the keto diet can be beneficial in the short term, women over 40 should be aware of specific risks and considerations:

1. Cholesterol and Heart Health

• Some women experience an increase in LDL cholesterol (“bad” cholesterol) and total cholesterol on keto, particularly when the diet is high in saturated fats.

• However, others see an improvement in HDL (“good” cholesterol) and triglycerides.

• Regular lipid panel monitoring is essential, especially if you have a family history of heart disease.

2. Bone and Muscle Health

• A very low-carb diet can reduce intake of magnesium, calcium, and potassium, which are vital for bone and muscle function — especially important after 40 when bone density naturally declines.

• Make sure you are checking levels and taking regular supplements to counteract any drops in these key nutrients.

3. Thyroid Function

• Extremely low-carb diets may lower levels of T3, the active thyroid hormone. While this may not always cause symptoms, it could be a concern for women already prone to hypothyroidism.

4. Gut Health

• Keto diets are often low in fiber unless carefully planned, which can affect digestion and microbiome diversity.

• Make sure you are getting a rich diet of leafy greens and a broad variety of low carb keto vegetables.

5. Sustainability and Nutrient Deficiency

• Long-term keto can be challenging to sustain, and restricting food groups may lead to deficiencies in certain vitamins, minerals, and phytonutrients if the diet isn’t well-balanced.

Can You Stay on Keto Too Long?

There’s no universal “safe” duration for keto, but most studies on its benefits in PCOS and insulin resistance have been short-term (3–6 months). Long-term research is limited, especially in women over 40.

Potential concerns with staying on keto indefinitely include:

• Persistently elevated LDL cholesterol

• Micronutrient deficiencies

• Reduced thyroid activity in some individuals

• Social and psychological strain from dietary restriction

Some experts recommend transitioning to a modified low-carb diet after the initial phase — one that allows more non-starchy vegetables, berries, legumes, and whole grains — to balance long-term health with metabolic benefits.

Practical Tips for Women Over 40 Considering Keto for PCOS or Insulin Resistance

• Work with a doctor or dietitian to monitor blood sugar, cholesterol, thyroid function, and nutrient status.

• Choose healthy fats like olive oil, avocados, nuts, and fatty fish instead of relying heavily on processed meats or butter.

• Include low-carb, fiber-rich vegetables to support gut health and provide essential micronutrients.

• Consider cycling carbs — introducing small amounts of healthy carbs periodically — to support thyroid and hormonal health.

• Avoid keto “junk food” products that are high in saturated fats and low in nutrients.

The Bottom Line

The keto diet may offer meaningful benefits for women with PCOS and insulin resistance, particularly in improving insulin sensitivity, lowering androgens, and supporting weight loss. However, for women over 40, it’s important to approach keto thoughtfully, with attention to heart health, bone health, thyroid function, and nutrient sufficiency.

Short-term use can be an effective tool — but long-term, a more moderate, nutrient-dense approach to low-carb eating may offer the best balance of metabolic improvement and overall wellness.