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Evidence Based

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How to Fix a Slow Metabolism

Written by Dr. Michael Ruscio, DC on October 31, 2023

Written by Dr. Michael Ruscio, DC on October 31, 2023 — Reviewed by Dr. Hannah Hamlin

Eating Right and Exercising Is Only Part of the Equation

• Understanding Metabolism|
• Calculating Your RMR|
• What Slows Down Your Metabolic Rate|
• Slow Metabolism and Hypothyroidism|
• How to Speed Up Your Metabolism|
• A Slow Metabolism Isn’t One Size Fits All|

We all likely know someone who seems to eat whatever they want — pizza and burgers, ice cream, chocolate, and potato chips — yet they still look relatively fit and healthy. Is a fast metabolism responsible for these unicorn people, while the rest of us struggle to keep off excess body fat with a slow metabolism? Not necessarily. 

In fact, it’s time to stop making the direct connection between a slow metabolism and weight gain. The causes behind weight gain are often much more complicated than your metabolic rate, and certainly more complicated than eating fewer calories than your body burns. Many other factors can contribute to weight gain, including thyroid health, stress level, toxin exposure, and your gut microbiome. 

In this article, we’ll explore all of these factors and more that impact your metabolism and provide a new way to think about correcting a slow metabolism, increasing energy levels, and losing weight. 

Understanding Metabolism and How Your Body Makes Energy

When we think about our metabolism, what we actually want to think about is how well our cells are able to make the energy we need to function. And primarily our energy production comes from our mitochondria, the tiny energy factories that number in the hundreds to thousands per cell. 

Ideally, your mitochondria are able to make energy by extracting nutrients from your food (primarily glucose) and turning that into ATP that can be used to power your cells. A lot of factors can impact your mitochondria: your diet, hormones, toxic burden, stress, and more. Now you’re starting to get a better idea of how complex your metabolism really is. 

Yes, overeating can cause you to gain weight (because you’re consuming more nutrients than you need for energy on a daily basis), but it’s not the same for everyone [1]. Research also shows that a slower metabolism doesn’t always equal weight gain, nor does a fast metabolism always equal weight loss [2]. And while overeating may cause weight gain, undereating may also cause the body to hold onto body fat — because it believes there is not enough food to be had, so it must store energy in the form of fat reserves for later use.

It’s also important to note that just because someone is skinny, it doesn’t mean they have a healthy metabolism. Even thin people may have too much fat relative to lean mass, which could slow down their metabolism and increase their risk for health complications like diabetes and cardiovascular disease [3]. 

Calculating Your Resting Metabolic Rate (RMR)

If metabolism and weight gain or loss are more than just calories in calories out, is it helpful to know our resting metabolic rate (RMR)? Your RMR is the rate at which you burn calories at baseline, without additional physical activity, each day. This can be helpful to know if you are wondering what your baseline daily calorie intake (also called total daily energy expenditure, or TDEE) should be and whether you are under or overshooting that intake. 

You might find that you actually need to eat more calories to reach your RMR, and that might be why your body is resistant to weight loss. This is because if you’re not eating enough, your body naturally slows down your metabolism to conserve energy and protect you from “starving.” But you need to expend energy to burn fat and use your muscles, so without it, weight loss becomes an impossibility. Feeling cold, depressed, and constipated are other signs your body is in “starvation mode [4].”

Knowing your RMR and TDEE can also help you figure out what ratio of protein, fat, and carbs you should be eating. You can find an online RMR and TDEE calculator here. 

What Slows Down Your Metabolic Rate

Your metabolism isn’t just based on how many calories you consume and how often you move (although those are both factors). These are the many factors that go into having a slower metabolism [3 5, 6]: 

• Poor diet (often too many carbohydrates, not enough protein)
• Undereating
• Stress
• Infection
• Toxins
• Imbalanced gut microbiome
• Poor thyroid function
• Hormone imbalances/changes, including menopause
• Inconsistent blood sugar levels, leading to insulin resistance
• Sedentary lifestyle
• Aging
• Genetics
• Chronic conditions
• Medications such as steroids, blood pressure reducers, antidepressants

What we can’t control: genetics and aging. We’re all getting older every day, and we all have the genes we have. Some of us may also need certain medications to function each day. It’s not worth getting hung up on these when it comes to improving your metabolism. 

Fortunately, improving many of the other factors impacting metabolic health may change the expression of certain genes we were born with. So while you can’t simply delete unfavorable genes from your DNA, you can sometimes control whether those genes are “turned on” or “turned off” via diet, lifestyle, and other intentional changes.

What we can control: diet, stress, toxins, gut health, and everything else. Chronic stress is one factor that often goes overlooked when it comes to having a healthy metabolism. Whether it’s mental, physical, or both, bouts of acute stress are good for the body, but extended periods of stress (high cortisol) can quickly impair mitochondria and affect metabolism. Chronic stress is also one of the most underappreciated causes of belly fat — sensing danger, the body holds onto fat around the middle to protect the central organs [7, 8]. 

Chronic infection and a high toxic burden may also slip under the radar and must be addressed to correct a sluggish metabolism, on both the level of the gut and the mitochondria [9, 10]. When the gut is overburdened by toxins and pathogens, it can’t metabolize food well to give you energy. With a leaky gut, these toxins make their way from the gut to your cells, damaging and slowing down the mitochondria you need to make energy. When the gut and the mitochondria are stabilized, your metabolism can keep up a lot more easily with the physical demands of the body. 

Slow Metabolism and Hypothyroidism

It’s important to note that what you might think is a slow metabolism could be an underactive thyroid (hypothyroidism). Many people with hypothyroidism struggle to lose weight no matter how much they exercise. In this case, supporting the thyroid gland is essential to correcting your metabolism and regaining energy. Then, other strategies like strength training can begin to make a difference in establishing a healthy body weight.

If you’re interested in getting to the bottom of your thyroid health and working with a professional to correct it if needed, please reach out and schedule a free consultation with us at the Ruscio Institute for Functional Health. Or, if you want to learn more first, you can check out our new online thyroid course. 

How to Speed Up Your Metabolism

Now that we know a bit more about the many potential causes of a “slow metabolism,” aka mitochondrial dysfunction, let’s dive into the ways to speed it up. Assuming you are addressing underlying causes like poor thyroid function or chronic infection, here are the best ways to improve a slow metabolism. 

Exercise, Especially Resistance Training

Exercise is important, but the goal should be to increase lean muscle mass. Lean muscle tends to burn up to 13x more calories than fat [3].

Recent evidence suggests that resistance training, typically 3 days per week, but not aerobic exercise (even with resistance training or an improved diet), can raise the metabolic rate by an average of 96 calories per day if you are replacing fat with equivalent weight of muscle [11].

This doesn’t necessarily mean you should never do aerobic exercise. But if improving your metabolism is the goal, increasing muscle mass should be the first priority. 

Increasing your Protein Intake

Eating a diet with a moderate or higher proportion (15–25%) of calories from protein appears to increase resting metabolic rate and promote muscle growth instead of fat building, which is not true for low-protein (5%) diets [1, 12]. 

More specifically, a higher-protein diet can contribute to:

• Weight loss and fat loss [13, 14, 15, 16]
• Better metabolic health [13, 15, 17, 18]
• Muscle gain [19, 20]
• Healthy aging [21, 22, 23]
• Gut health [24, 25]

If your goal is to build muscle, a good starting point for your protein intake is 1–1.2 g/kg of body weight/day [26]. For someone who’s goal weight is 150 lbs, this would be 68–82 grams of protein per day. If that sounds like a lot to you, don’t be afraid to slowly increase your protein intake over time. You can start by prioritizing a high-protein breakfast. 

Improving Gut Health

While there isn’t enough scientific evidence to conclude that interventions for improving gut health affect human energy metabolism, we can speculate that malabsorption likely impedes metabolism by preventing the body from using the nutrients it needs to create energy [27]. We also know that the gut microbiome can influence how our bodies use energy, but there’s no clear and consistent way to modify it for better energy metabolism yet [28]. 

Regardless, a healthy gut microbiome is good for your overall health, and a gut that is dysregulated or burdened with chronic infections is not doing you or your energy levels any favors. If you suspect gut issues are a key part of why you have low energy or can’t lose weight, absolutely pursue treatments to correct your gut health alongside a healthy diet and lifestyle. 

Gut conditions that may be affecting nutrient absorption and metabolism include:

• IBS
• SIBO
• IBD
• Autoimmune gastritis
• Chronic constipation

Probiotics are a great place for most people to start to regulate the gut and help the body break down and use nutrients from food more efficiently. 

A Slow Metabolism Isn’t One Size Fits All

If you’ve always believed or you’ve been told that a slow metabolism is the sole reason why you feel sluggish and tired and can’t lose weight, know that isn’t the whole story. Many factors, including thyroid status, gut health, stress, and toxic burden can greatly impact how your body creates and burns energy. The strategy to “fix” your metabolism may not be as straightforward as exercising more and eating healthy — you may have to look a little deeper into your gut microbiome status, stress levels, and other individual factors. 

If you’re interested in working with a health coach to improve your metabolism and feel energized again, reach out to us at the Ruscio Institute for Functional Health.

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.