Is It Really My Metabolism? What a Slow Metabolism Means and How a Doctor Can Check

What metabolism really means

Metabolism is how your body burns calories to keep you functioning. It helps determine how many calories you need every day to maintain your weight, lose weight, or gain weight.

The largest part of it is your resting metabolism, which is the energy your body uses simply to stay alive while you sit still: breathing, pumping blood, regulating your hormones, and repairing your cells. The rest comes from digesting food, which the Mayo Clinic estimates uses about 10 percent of the calories you eat, and from movement. That includes your workouts, and it also includes all the walking, standing, and fidgeting you do through the day, which on its own can account for anywhere from 100 to 800 calories daily.

This is why two people who eat the same meals and follow the same exercise routine can still end up with very different results. Each of these parts of metabolism differs from one person to the next, and the biggest difference usually comes from what the body is made of.

Same weight, different bodies

Here is something that surprises many of my patients. Two people can weigh exactly the same, yet one can eat significantly more than the other without gaining weight.

Imagine two women who are the same height and both weigh 170 pounds. The first has spent years lifting weights and carries a good amount of muscle. The second has been through several rounds of strict dieting, and each time she lost weight, some of what she lost was muscle. On a standard bathroom scale, these two women look identical. Inside their bodies, they are very different, because muscle burns more calories at rest than fat does. The first woman's body uses more energy every hour of the day, even while she sleeps, so she can eat more and still hold her weight steady. The second woman may gain weight eating the very same meals.

That is why I do not judge a patient's metabolism by the number on the scale. What your body is made of tells me far more than what it weighs. Your muscle mass, body fat, age, hormones, and activity level all play a role in how many calories your body burns, and two people with the same weight can need completely different plans.

Does metabolism really slow down with age?

Many people assume their metabolism simply started to fade sometime in their thirties or forties. A large international study published in Science in 2021, which measured the energy use of thousands of people from infancy to old age, found something different. Once the researchers accounted for differences in body size and muscle, metabolism stayed remarkably stable between the ages of about 20 and 60, and only began to decline more noticeably after 60.

I find this reassuring for my patients, because it means the slowdown many people feel in midlife usually has a specific cause. The most common ones are a gradual loss of muscle, hormonal changes, less movement during the day, and the effects of years of dieting. Each of these can be measured, and many of them can be treated, which gives us something real to work with.

Looking beyond the scale

At Qua Wellness & Med Spa, we use advanced body composition analysis, which tells us much more than an ordinary scale can. It helps us estimate your resting metabolism and measure your muscle mass, your body fat, and your visceral fat. Visceral fat deserves a special mention. It is the fat stored deep inside your abdomen, wrapped around organs such as your liver, pancreas, and intestines, and it behaves very differently from the fat you can pinch under your skin. According to the Cleveland Clinic, too much visceral fat is linked to a higher risk of heart disease, and it is also associated with diabetes. You cannot see it in the mirror or on a bathroom scale, which is exactly why measuring it is so useful. This information helps me understand your body as it really is. It shows me whether your resting metabolism is lower than expected, whether you have lost muscle along the way, and where your body is storing fat. It also lets us track the right things as you progress, because losing fat while keeping your muscle is a very different result from simply watching the scale go down.

Why metabolism slows down

There are many possible reasons, and most patients I see have more than one. An underactive thyroid lowers the rate at which your body burns energy. Loss of muscle, whether from aging, inactivity, or dieting, removes some of the tissue that burns the most calories at rest. Hormonal changes, including those around menopause, can shift where and how your body stores fat. And repeated dieting can teach your body to run on less.

Other conditions, including insulin resistance, iron deficiency, vitamin deficiencies, and electrolyte abnormalities, may not lower your metabolism directly, but they can cause fatigue and reduce how active you are, which makes your weight harder to manage. I explain several of these in more detail in my earlier article, You're Doing Everything Right. So Why Isn't the Scale Moving?

The yo-yo cycle

Many of my patients know this pattern well. You lose weight, and then you gain it back. You diet again, you lose weight, and once more it returns. Over time, especially with very restrictive diets, this cycle can work against you. Each time you lose weight quickly, some of what you lose is muscle, and the weight that returns is often more fat than muscle. Your body also adapts to the lower intake by burning fewer calories, almost as though it is trying to protect you from starvation. Researchers who followed contestants from the television show The Biggest Loser found that six years later, their resting metabolism was still about 500 calories a day lower than expected for their size. So if you have been through several rounds of dieting and feel that each one works less well than the last, you are describing something real that happens in the body.

So can we do something about it?

Absolutely. The first step is to understand what is happening inside your body, because the right plan depends entirely on the cause.

At Qua Wellness & Med Spa, we investigate. We evaluate your body composition, review your medical history, check for possible hormonal or nutritional problems, and look for the missing piece of your puzzle. When we identify a treatable problem, such as an underactive thyroid or insulin resistance, we address it directly.

From there, much of our work focuses on protecting your muscle and improving your metabolic health, so that the weight you lose is fat and your metabolism is not pushed lower along the way. That usually means making sure you eat enough protein, building strength in a way that suits your body and your schedule, and avoiding the kind of crash dieting that sets up the next round of the yo-yo cycle. Then we use your body composition results to follow your progress, so you can see the muscle you are keeping and the fat you are losing, even in weeks when the scale barely moves.

One patient's story

One of my patients had been trying very hard to lose weight for a long time. Her weight had come to interfere with much of her life, including her hopes of having children, and by the time she came to see me, she was deeply frustrated. We looked more deeply into her problem, and that meant a special test. Some hormones are released in bursts rather than at a steady rate, so a random blood test can easily miss a problem with them. So we measured one of these hormones in her urine over a full 24 hours, and sure enough, that test gave us the answer we had been looking for.

With the right referral and the right medicine, everything began to change. Six months later, she is 100 pounds lighter. Her body composition analysis tells the rest of the story, showing her total body fat, her visceral fat, and her muscle mass. Interestingly, the analysis also estimates a metabolic age, and hers has come down significantly.

Where to go from here

After 30 years of practicing endocrinology, the most important thing I have learned is that weight loss has to be fitted to the person. Two people may weigh the same, but they rarely need the same treatment, and a plan built for your body will always do more for you than one built for the average patient.

If you have been wondering whether a slow metabolism is holding you back, I would be glad to help you find out. You can request an appointment at our Burr Ridge clinic here, and you can follow us on Instagram at @quawellnessandmedspa to hear real patient stories about what was holding them back and how we helped them move forward.

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