Your Metabolism Probably Isn’t “Broken” — It’s Burned Out From Everything You’ve Put It Through

By: Marcy Schoenborn

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If you’ve ever thought, “My metabolism just isn’t what it used to be,” you’re not imagining the symptoms — but the cause is rarely an actual metabolic disorder.
Most of the time, it’s the cumulative effect of stress, under-eating, restrictive dieting cycles, hormonal shifts, poor sleep, and inconsistent fueling patterns that confuse your body into slowing things down for survival.

Let’s break down what’s really going on.

1. Yo-Yo Dieting Trains Your Body to Burn Fewer Calories

Every time you start a new restrictive diet, lose weight quickly, then regain it, your metabolism takes a hit.

Repeated weight loss and regain — known as weight cycling — lowers resting metabolic rate, increases fat storage efficiency, and raises cortisol. Studies show that weight cycling can reduce metabolic rate beyond what’s explained by weight loss alone and increases the likelihood of future weight gain.

In other words:
Your body learns to protect you by burning fewer calories because it no longer trusts that consistent nourishment is coming.

2. Intermittent Fasting When You’re Undernourished Backfires

Intermittent fasting is a tool — not a religion.
And like any tool, it can absolutely make things worse if used at the wrong time.

If someone is:

• already under-eating,

• chronically stressed,

• skipping nutrients their hormones require,

• or dealing with poor sleep…

• or when you're not sugar detoxed for 21 days

…then tightening the feeding window just deepens the deficit.

Research shows that chronic energy restriction elevates cortisol and may reduce thyroid hormones like T3, which are essential for metabolic rate.

So if you’re fasting but barely hitting 60% of your nutrient needs during your eating window?
The body doesn’t interpret that as “fat-burning mode.”
It interprets it as “famine.”

3. Stress Is a Metabolism Killer — Full Stop

High cortisol from chronic stress changes:

• where you store fat,

• how effectively you use glucose,

• your appetite signaling,

• and your thyroid hormone conversion.

Chronic stress is strongly linked to metabolic slowdown, visceral fat accumulation, and impaired insulin sensitivity.

If your stress is through the roof, your metabolism is on the brakes — even if you’re “doing everything right.”

4. Under-Eating Protein and Micronutrients Slows Down Every System

Your metabolism isn’t just “calories in vs. calories out.”
It’s cellular activity — enzymes, hormones, muscle repair, mitochondrial function.

(Then add in all the pressure to eat more protein without an education of how it works in your body, the quality of the protein, it is not all created equal, and how much you need based on your lean body mass. There is a science to how much protein is healthy, and it isn't what most people are teaching.)

If you’re lacking:

• B vitamins

• magnesium

• essential amino acids

• omega-3s

• iodine

• iron

…your cells literally cannot produce energy efficiently.
Micronutrient deficiencies are directly associated with reduced metabolic efficiency, insulin dysregulation, and impaired thyroid function.

This is why women often feel like their metabolism tanked — but when they start eating enough, everything lights back up again.

5. Too Much Cardio + Not Enough Strength Training

A lot of women unintentionally pair under-eating with long cardio workouts.

Cardio is great — but when paired with low energy intake, the body compensates by slowing resting metabolism and breaking down muscle tissue.

Muscle is the most metabolically active tissue you have.
Lose muscle → lose metabolic rate.
It’s that simple.

Strength training, on the other hand, increases resting energy expenditure and insulin sensitivity.

6. Poor Sleep Disrupts Every Hormone Involved in Metabolism

One night of poor sleep reduces insulin sensitivity by up to 25%.
Chronic sleep loss elevates cortisol, increases appetite (ghrelin), lowers satiety (leptin), and dysregulates thyroid function — all of which slow metabolic activity.

If sleep is a mess, metabolism follows.

7. Perimenopause & Hormonal Shifts Add Fuel to the Fire

Hormonal changes aren’t the cause of a “broken metabolism,” but they are an amplifier of the underlying issues.

Estrogen plays a major role in glucose regulation, fat distribution, and metabolic rate. Declining levels during perimenopause can alter how the body uses energy, especially if metabolic resilience is already low.

But hormone changes aren’t destiny.
A nourished, strength-trained, well-rested body handles perimenopause far better than a depleted one.

8. Your Metabolism Isn’t Damaged — It’s Adaptive

Your metabolism isn’t stubborn.
It’s obedient.

It adapts to the environment you create:

• Feed it too little → it slows down.

• Stress it too much → it conserves energy.

• Sleep too little → it shifts fuel storage.

• Lose and regain weight repeatedly → it becomes more efficient at storing fat.

• Build muscle + feed adequately → it speeds up.

The good news?

A downshifted metabolism can absolutely recover.
But the solution isn’t more restriction — it’s rebuilding trust with your body.

So When You Think Your Metabolism Is “Off”…

It’s usually this cocktail:

• years of dieting

• under-eating

• fasting without fuel

• chronic stress

• low muscle mass

• poor sleep

• micronutrient gaps

• hormonal transitions

Your metabolism didn’t break.
It just adapted to survive.

And now it needs support to thrive again.