Millions of people think they’ve tried everything to lose weight, from more cardio and fewer carbs to earlier bedtimes.

But for many, they still hit a weight-loss wall at no fault of their own and for reasons beyond their control: a slow metabolism. 

A slow metabolism typically manifests itself as low energy, weight gain and stalled weight loss, but it can also impact blood sugar, circulation, muscle function and several other bodily functions that can play a role in weight loss or gain. 

‘When someone says they have a “slow metabolism,” it’s usually not a diagnosis. It’s a feeling. And most of the time, it’s a shorthand for “I don’t feel like my body is working the way it used to,”’ California-based registered dietitian Melanie Murphy Richter told the Daily Mail.

‘From a clinical standpoint, metabolism is much bigger than calorie burn. It’s how your body is making and using energy, how stable your blood sugar is, how well you’re maintaining muscle, how your circulation is functioning, and even what’s happening at the cellular level.’

Richter added: ‘When something is “off,” it’s rarely just one thing. It’s usually a combination of shifts that we also see tied to aging.

‘Things like insulin resistance, changes in mitochondrial function, loss of muscle, or early changes in cardiovascular health.’

And when these underlying issues take hold, the body becomes less efficient at using energy. So the same calories someone ate five years ago now stick around as fat; the same workout that used to trim them down now barely moves the needle. 

The body might sometimes leave clues that a metabolic issue is behind weight gain. One major clue is fat building deep in the belly. Persistently high insulin levels push the body to store more energy as fat while making it harder to break that fat down (stock image)

When clients come to her with unexplained weight gain or weight-loss plateaus, Richter pays attention to several signs that metabolic dysfunction may be the cause. 

She particularly looks at abdominal fat – weight gain in the midsection.

‘It’s less about the number on the scale and more about where the weight is going,’ Richter said. ‘An increase in abdominal fat tends to reflect changes in insulin sensitivity and is more closely tied to metabolic and cardiovascular risk.’

A range of other symptoms point to potentially dangerous metabolic problems that, together, raise the odds that a person will stop losing weight and even gain weight.

Slower digestion, such as chronic constipation or gut sluggishness, is often the clearest early warning that metabolism isn’t working properly. 

‘Your body might sometimes leave clues that something metabolic is going on,’ Dr Jody-Ann McLean, a women’s hormonal and metabolic health expert, told the Daily Mail.

This often shows up as fat building up deep in the belly. Over time, persistently high insulin levels push the body to store more energy as fat while making it harder to break that fat down, a pattern closely linked to insulin resistance.

And worsening insulin resistance can lead to prediabetes, raising the risk of full-fledged diabetes later in life. 

Hormones can also play in this resistance, especially for women.  

McLean added: ‘For women in midlife, if you’re putting on weight, especially central abdominal weight, despite exercise and dietary changes, a big contributing factor could be declining estrogen levels in perimenopause, which can worsen insulin sensitivity.’

And stubborn weight isn’t the only red flag that you may be experiencing metabolic issues.  

Frequent blood sugar swings — feeling shaky or irritable unless eating every few hours — or a deep exhaustion that sleep won’t fix, along with feeling cold more often, especially in the hands and feet, can point to blood sugar, cellular energy production or thyroid issues.

Blood test results trending in the wrong direction, like rising fasting glucose, A1c, insulin or shifting lipids, frequently reveal what your body is trying to tell you and can provide a clearer diagnosis.

‘When someone says they have a “slow metabolism,” it’s usually not a diagnosis. It’s a feeling. And most of the time, it’s a shorthand for “I don’t feel like my body is working the way it used to,”’ California-based registered dietitian Melanie Murphy Richter told the Daily Mail

Exercise helps muscles take up glucose without needing as much insulin, reducing demand on the pancreas, lowering weight and improving insulin sensitivity over time (stock)

And the good news is that once the true cause is revealed, it can be fixed.

McLean said: ‘If you’re having significant unintentional weight changes, whether it’s losing or gaining weight, this is always worth discussing with your doctor. Be specific and arrive to your doctor’s consultation with details.

‘Describe what’s actually happening and what you’re worried about. Write down how much weight you’ve gained and over what period of time, mention if it’s despite making improvements in diet or exercise.’

Exercise is a key tool. Walking, strength training or even short bursts of movement throughout the day help muscles take up glucose without needing as much insulin, which reduces demand on the pancreas and improves insulin sensitivity over time.

Nutrition matters just as much. Prioritizing whole foods like vegetables, lean proteins, whole grains and healthy fats — particularly in a Mediterranean-style diet — has strong evidence for improving metabolic health.

Dr Jody-Ann McLean, a women’s hormonal and metabolic health expert, told the Daily Mail: ‘‘If you’re having significant unintentional weight changes, whether it’s losing or gaining weight, this is always worth discussing with your doctor’

Sleep and stress management are often underestimated but directly affect how the body handles insulin; chronic sleep loss and ongoing stress raise cortisol, which worsens insulin resistance.

‘It’s not really that your metabolism is broken, it’s often that your body is doing exactly what it was designed to do, but in an environment it was never meant to handle long-term,’ McLean said.

Richter added: ‘Metabolism is also not just about weight. It’s tied to how well you’re aging.’ 

As people age, several biological shifts can make metabolism less efficient, including declining insulin sensitivity, loss of muscle mass and changes in how cells produce energy. 

For women in midlife, dropping estrogen levels during perimenopause can worsen insulin resistance, often leading to abdominal weight gain even when diet and exercise haven’t changed. 

These age-related changes are real, but they are not fate. 

The good news is that targeting the underlying drivers through lifestyle changes can improve metabolic health at any age.