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Why It Fails Women Over 40, Especially During Perimenopause and Postmenopause

For many years, intermittent fasting has been promoted as a healthy approach to weight loss, weight maintenance, and overall health. However, as a clinical nutritionist who relies on evidence-based and clinically proven practices, I have consistently disagreed with intermittent fasting.

I am especially concerned when intermittent fasting is recommended to women over 40 who are experiencing perimenopausal symptoms or who are living in postmenopause. During these stages of life, the body is already under hormonal stress, and strategies that add more stress often backfire.

Quick note for clarity: menopause is a single point in time, defined as the day a woman has gone 12 straight months without a period. The stages that matter most for symptoms and health changes are perimenopause (before that point) and postmenopause (after it).

This article is written for women dealing with fatigue, poor sleep, hot flashes, stubborn belly fat, mood changes, or declining energy, and who have been told that skipping meals is the solution. For many women in perimenopause and postmenopause, intermittent fasting does not improve health. It often makes symptoms worse.

The reason is not a lack of discipline. It is biology.

For women over 40, especially those in perimenopause or postmenopause, intermittent fasting often leads to skeletal muscle loss, and that muscle loss alone can slow metabolism, weaken bones, and significantly increase heart risk [1,6].

Why So Many People Promoted Intermittent Fasting, Then Went Quiet

At one time, celebrities and influencers openly promoted intermittent fasting. Public figures such as Jennifer Aniston, Chris Pratt, and Kourtney Kardashian shared fasting routines in interviews and online posts.

Some physicians also supported time-restricted eating, including Peter Attia and Ethan Weiss.

But today, many of these voices are quieter or have changed their position.

As more women entered perimenopause and postmenopause, and as longer-term data became available, the downsides of intermittent fasting became harder to ignore. One issue that repeatedly stood out was the loss of skeletal muscle, which drives metabolic slowdown, bone loss, and increased cardiovascular risk [1,6].

Why the Message Changed

Early enthusiasm for intermittent fasting focused primarily on short-term weight loss rather than long-term health.

Over time, the same concerns appeared again and again:

• • Muscle loss occurred, even when scale weight went down [1,6]
  • Energy and exercise recovery declined
  • Hormone balance suffered as estrogen declined [4]
  • Bone density concerns increased [7]
  • Heart and metabolic risk factors rose, despite weight loss [8]

Peter Attia later shared that extended fasting led to loss of lean muscle, prompting him to move away from long fasts. Ethan Weiss stopped recommending intermittent fasting after leading a clinical trial showing no meaningful advantage over regular eating patterns [5].

As a result, many experts no longer promote intermittent fasting as a one-size-fits-all solution, particularly for women in midlife.

Why Skeletal Muscle Matters So Much After 40

Skeletal muscle is not just for strength or appearance. It is a major organ that protects long-term health [6].

Muscle helps:

• • Burn calories at rest [6]
  • Regulate blood sugar [6]
  • Support strong bones [7]
  • Protect heart health [8]
  • Maintain energy and independence

As women age, they naturally lose muscle, a condition called sarcopenia [1,2]. This loss accelerates as estrogen declines, which is common in perimenopause and postmenopause [4].

When intermittent fasting is added during this phase, muscle loss often accelerates.

Why Women with Perimenopausal or Postmenopausal Symptoms Do Not Benefit from Intermittent Fasting

When a woman is in perimenopause or postmenopause, her body is already under increased stress.

During these stages:

• • Estrogen levels decline
  • Cortisol rises more easily
  • Muscle loss accelerates
  • Bone density becomes harder to maintain
  • Blood sugar and insulin regulation become less stable

Intermittent fasting adds more stress to an already stressed system.

For women experiencing symptoms such as:

• • Fatigue
  • Hot flashes
  • Sleep problems
  • Anxiety or mood changes
  • Weight gain around the midsection

Intermittent fasting often worsens symptoms, rather than improving them.

Long fasting periods:

• • Raise cortisol, worsening sleep, and hot flashes [4,6]
  • Reduce muscle-building signals needed to protect metabolism [1,3]
  • Increase muscle loss when estrogen protection is already low [1,4]
  • Reduce bone-supporting signals at a critical time for bone health [7]

This is why perimenopause and postmenopause are not times for extended periods without nourishment. They are a time for stability, strength, and support.

How Intermittent Fasting Promotes Muscle Loss

1. Long Fasting Raises Stress Hormones

Extended fasting raises cortisol, a hormone that breaks down muscle for fuel. Women over 40 are more sensitive to this effect as estrogen declines [4,6].

2. Skipping Meals Means Missed Muscle Repair

Muscle requires regular protein intake spread throughout the day to stay healthy [3].

When meals are skipped:

• Muscle-building signals are missed
• Muscle breakdown exceeds muscle building

Eating all protein in a short window does not fully protect muscle [3].

3. Lower Estrogen Makes the Problem Worse

Estrogen helps regulate muscle protein balance.

After 40, especially in perimenopause and postmenopause:

• • Muscle breaks down more easily
  • Recovery slows
  • Fasting stress causes greater muscle loss

This is supported by research on estrogen and muscle protein balance [4].

Even Small Muscle Loss Can Triple Heart Risk

Many people believe muscle loss only matters when it is severe. That assumption is incorrect.

Research published in The American Journal of Medicine found that adults with low skeletal muscle mass had up to a three-fold (about 300 percent) higher risk of heart attack and early death, even after adjusting for body weight and body fat [8].

In practical terms, when around 8 percent of weight loss comes from skeletal muscle, which commonly occurs during aggressive dieting or prolonged fasting, cardiovascular risk rises sharply.

Muscle loss is not cosmetic. It is a major cardiovascular risk factor.

What Muscle Experts Say About Intermittent Fasting

One of the strongest critics of intermittent fasting for women is Dr. Don Layman, a leading researcher in protein metabolism, skeletal muscle preservation, and aging.

Dr. Layman is a Professor Emeritus at the University of Illinois, where he spent decades studying how muscle is built, maintained, and lost as people age. His research helped shape much of what we know today about protein timing, protein quality, and muscle protein synthesis, especially in adults over 35.

His work consistently demonstrates that skeletal muscle requires regular, evenly spaced protein intake throughout the day, rather than long periods without food.

Because of this, Dr. Layman has repeatedly warned that intermittent fasting is detrimental to muscle preservation in women, particularly after age 35, when muscle loss naturally accelerates.

He explains that skipping meals and delaying protein intake:

• • Reduces muscle protein synthesis
  • Increases muscle breakdown
  • Makes it harder to maintain lean mass with age

In simple terms, his message is clear:

Muscle does not respond well to long gaps without protein, especially as we age.

This position aligns closely with clinical research showing that prolonged fasting accelerates muscle loss, slows metabolism, and increases long-term health risks in women over 40, especially during perimenopause and postmenopause [1,3,6].

Why Intermittent Fasting Seems to Work at First

Early weight loss from intermittent fasting often comes from:

• • Water loss
  • Glycogen loss
  • Reduced food intake

This is not equivalent to losing body fat or improving metabolic health [6].

If muscle is lost during this process, long-term health outcomes worsen. 

[Learn more about the 8-Week Fat Loss Challenge]

What Women Over 40 Actually Need Instead

Women over 40, especially those in perimenopause or postmenopause, tend to do better with:

• • Regular meals that include protein [3]
  • Eating patterns that reduce stress on the body
  • Strength training to protect muscle and bone [7]
  • Nutrition that supports insulin balance, not extreme restriction

Fat loss comes from metabolic health, not prolonged fasting.

The Bottom Line

Intermittent fasting may sound healthy, but for many women over 40, especially those in perimenopause and postmenopause, it causes more harm than good.

It can:

• • Increase skeletal muscle loss [1,6]
  • Slow metabolism [6]
  • Weaken bones [7]
  • Increase heart attack and early death risk by up to three times when muscle loss occurs [8]

If a plan costs you muscle, it costs you long-term health.

Protecting muscle protects metabolism, bones, and the heart.

Have Questions or Want Personal Guidance?

If this article raised questions or helped you see intermittent fasting differently, you do not have to figure out the next steps alone.

If you have questions, please email me directly at robert@dietfreelife.com. I read these messages personally and am happy to point you in the right direction.

You can also schedule a free consultation to get answers to your questions and learn more about the different programs we offer, including options designed specifically for women in perimenopause and postmenopause. During this conversation, we will explore what may be the best fit for your goals, health history, and stage of life.

There is no pressure, just clarity, education, and support.

References

1. 1. Mitchell, W.K., et al. (2012). Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength. Journal of Applied Physiology, 113(2), 329–337.
   2. Janssen, I., et al. (2000). Skeletal muscle mass and distribution in 468 men and women aged 18–88 yr. Journal of Applied Physiology, 89(1), 81–88.
   3. Phillips, S.M. (2014). A brief review of higher dietary protein diets in weight loss. Applied Physiology, Nutrition, and Metabolism, 39(5), 597–602.
   4. Hansen, M., et al. (2010). Effects of estrogen on muscle protein synthesis and muscle mass. Journal of Clinical Endocrinology & Metabolism, 95(9), 4114–4123.
   5. Weiss, E.P., et al. (2020). Effect of time-restricted eating on weight loss and metabolic health. JAMA Internal Medicine, 180(11), 1491–1499.
   6. Wolfe, R.R. (2006). The underappreciated role of muscle in health and disease. American Journal of Clinical Nutrition, 84(3), 475–482.
   7. Cooper, C., et al. (2011). Muscle strength, bone mass, and fracture risk. Osteoporosis International, 22(6), 1711–1725.
   8. Srikanthan, P., & Karlamangla, A.S. (2014). Muscle mass index as a predictor of longevity. American Journal of Medicine, 127(6), 547–553.
   9. Layman, D.K. (2014). Protein quantity and quality at levels above the RDA improves adult weight loss. Journal of the American College of Nutrition, 33(sup1), 15–22.

__________
Robert Ferguson is a California- and Florida-based single father of two daughters, clinical nutritionist, Omega Balancing Coach™, researcher, best-selling author, speaker, podcast and television host, health advisor, NAACP Image Award Nominee, creator of the Diet Free Life methodology, and Chief Nutrition Officer for iCoura Health. He also serves on the Presidential Task Force on Obesity for the National Medical Association and the Health and Product Advisory Board for Zinzino, Inc.

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