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What Causes Slow Metabolism — And How Can You Boost It?


By: Erin Coleman, B.S. - Nutritional Science, R.D., L.D.,

Writer at The Fit Father Project

what causes slow metabolism

Answering the question “what causes slow metabolism” is the best way to make healthy lifestyle changes, increase energy expenditure, and reduce your risk of unwanted weight gain.

Metabolism tends to decrease with age but many factors contribute to the rate at which your body burns calories throughout the day.

Learning more about what causes slow metabolism and ways to boost it can dramatically improve your health and quality of life!

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What Causes Slow Metabolism?

If you have a slow metabolism, your body likely burns fewer calories than other people in the same age and gender group.

You might have friends who eat twice as much as you, but don't ever seem to gain weight.

So what really causes slow metabolism?

Numerous factors can contribute to it, including:


Metabolism tends to decrease with age, partly because of decreases in muscle mass associated with aging.

The American Council on Exercise (ACE) reports that metabolism usually decreases 1-2% per decade of life, which equates to about 150 calories every 10 years after age 20.

However, getting older doesn't mean you're stuck with a slow metabolism, as simple lifestyle changes can give it a boost!


Genetics also play a role in having a slow metabolism, as some people are genetically prone to burning fewer calories daily than others.

If your family members have a slow metabolism, you might too.

However, despite your genetic makeup, speeding up a slow metabolism is still possible!

Low Testosterone

Low testosterone levels often affect aging men, as testosterone can decrease at a rate of just over 1% each year of life after age 40.

Low testosterone, or low T, can slow metabolism and put you at risk of unplanned weight gain, increased body fat, and decreases in lean muscle mass.

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Muscle/Fat Ratios

Aging, and testosterone decline often associated with it, can cause decreases in muscle mass and increased body fat.

This process often decreases your body's metabolic rate.

Regular exercise is one of the best ways to improve your muscle/fat ratio and give your metabolism a boost!

Low Activity Levels

Sitting down too much is a leading cause of slow metabolism.

Many people with desk jobs find themselves sitting down more than 8 hours every day!

Find ways to stand up, walk, or climb stairs often throughout the day in addition to making time for scheduled exercise most days of the week.

Skipping Meals

What causes slow metabolism?

Prolonged fasting by skipping meals can make your body go into starvation mode and burn fewer calories!

You don't have to skip meals or feel hungry to effectively achieve or maintain a healthy weight.

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15 Way to Boost a Slow Metabolism

Regardless of how slow your body's metabolic rate is, there are always ways you can give it a boost!

Try the tips below to look and feel better without feeling hungry.

Eat Enough Calories

Even if your goal is weight loss or fat loss, you don't have to starve yourself to get lean.

In fact, the opposite is true.

Eating during regular mealtimes can keep your metabolism going strong.

If you'd like to drop weight, aim to burn 500-1,000 more calories than you eat daily.

The National Heart, Lung, and Blood Institute (NHLBI) recommends men consume 1,500-1,800 calories per day for effective weight loss.

However, your individual needs vary based on your size, age, activity level, and metabolic rate.

Step on the scale daily or weekly to ensure your current energy intake is appropriate.

Build Muscle Mass

Building muscle mass using strength training is one of the most effective ways to increase your body's metabolic rate.

Aim to lift weights (you can also use resistance bands or your own body weight as resistance) at least 3-5 days each week.

Train all major muscle groups (quadriceps, hamstrings, calves, glutes, back, abs, chest, biceps, triceps, and shoulders) at least twice weekly if you can.

To get started, try these strength training workouts!

Try HIIT Workouts

Studies show that high-intensity interval training (HIIT), is an effective way to burn fat, increase muscle mass and strength, and boost a slow metabolism.

To complete HIIT training, alternate high-intensity exercise bouts with lower-intensity recovery periods.

Sprint for 30-60 seconds at a time followed by 60 seconds of jogging or cycling comfortably.

Or, try these HIIT workouts for men!

This HIIT bodyweight workout for fat loss can be done from inside your home with NO equipment!

Eat Extra Protein

Protein is a natural metabolism-booster, as studies show it speeds up total and resting energy expenditure.

Protein also boosts satiety and helps you build or maintain muscle mass, which further speeds up your metabolism.

Fill at least half of each plate of food with chicken, turkey, duck, fish, shrimp, seafood, lean organic red meat, eggs, or plant-based meat alternatives.

Consume three servings of milk, protein-fortified plant milk, Greek yogurt, plain kefir, cottage cheese, or cheese.

Add in protein shakes, protein bars, peas, beans, lentils, other legumes, nuts, seeds, nut butter, or hummus!

Eat protein at each meal and snack to keep your metabolism going strong.

Sleep More

Getting enough sleep enhances your metabolism for numerous reasons.

Having plenty of uninterrupted rest allows your body to better balance its hormones.

Gaining energy from a good night's sleep allows you to stay physically active, which keeps your metabolism elevated.

Aim to get at least 7-9 hours of sleep each night by setting a regular bedtime, sleeping in a cool dark room, not smoking or drinking at night, and avoiding hunger, feeling overly full, and looking at blue light right before bed.

This includes phones, computers, tablets, and television screens.

Consume Coffee or Tea

Drinking caffeinated coffee or tea is a metabolism booster, as studies show caffeine increases energy expenditure and decreases energy intake.

Components found in green tea called catechins, which are powerful antioxidants, can also increase your body's metabolic rate.

While coffee and tea both boost energy and your metabolism, they contain just 5 calories (or less) per serving — so you don't have to worry about consuming too many calories or weight gain.

Don't overdo it when it comes to caffeinated beverages though.

Consuming up to 400 milligrams of caffeine daily appears to be safe for most healthy adults.

This equates to about 4 cups of brewed coffee each day.

Try MCT Oil

Ingesting MCT oil, or oil containing large amounts of medium-chain triglycerides, is another effective metabolism-boosting strategy.

Examples of oils rich in MCT include coconut oil, palm kernel oil, and MCT supplements.

Studies show that MCTs can increase energy expenditure and decrease body fat in overweight men.

Consider MCT supplements or add coconut oil to shakes, smoothies, homemade protein bars, Greek yogurt, or even oatmeal.

Focus on Plant Foods

Diets containing primarily plant-based foods offer numerous health and wellness benefits, including lower chronic disease risks and higher metabolism.

Studies show that plant-based diets can reduce body fat by increasing satiety, reducing calorie intake, enhancing weight loss, and increasing energy expenditure.

The fiber found in plant foods fills you up but isn't fully absorbed or digested by your body.

While you don't have to follow a diet that's entirely plant-based, aim to eat plenty of nuts, seeds, vegetables, fruits, whole grains, peas, beans, and other legumes.

Add in coconut oil, olive oil, avocados, and other healthy fats!

Drink Water When You Wake Up

Water is another natural metabolism booster, and many people don't drink as much water as they should to maintain optimal health.

Since your metabolism decreases during sleep, drink 2-4 cups of water when you first wake up each morning to stimulate calorie burning.

Then, have coffee or tea plus your breakfast.

While everybody is different, many men have fluid intake requirements of 16 cups per day.

Learn how to hit your daily hydration levels!

Take Metabolism-Boosting Supplements

Taking certain dietary supplements for men can keep your metabolism high.

Vitamins, particularly B vitamins, are involved in many of your body's metabolic processes.

When choosing a multivitamin, pick one containing B vitamins, vitamin D, iron, calcium, zinc, and magnesium.

Testosterone-boosting supplements that increase your body's natural testosterone levels can also increase a slow metabolism, as testosterone enhances muscle-building and decreases muscle loss associated with aging.

Studies show that drinking green tea OR ingesting green tea extract also increases energy expenditure, boosts fat-burning, reduces fat absorption, and aids in weight loss.

Ask your doctor before taking any type of dietary supplement, especially if you're taking medications.

Don't Fast for Long Periods

Intermittent fasting is a weight-loss strategy that's effective for some people, but you don't have to skip meals or feel hungry to achieve or maintain a healthy weight.

Avoid long periods of fasting if you want your metabolism to stay high.

Studies show that prolonged fasting results in decreased energy expenditure, a higher body weight, and more fat mass.

Your body's natural response to starvation is to preserve energy by slowing down its metabolism.

Aim to eat three regular meals throughout the day, even if they are small meals or meal replacement protein shakes, with snacks in between as needed.

Avoid going more than 4-5 hours during the day without food.

Save fasting for night time when you're sleeping, or try less restrictive versions of fasting by eating during an 8-hour window of time (10:00 am to 6:00 pm).

Eat Chili Peppers

Studies show that chili peppers and other sources of capsaicinoids, such as pepper extracts, can also give your metabolism a boost.

Researchers found that capsaicinoids decrease percent body fat and total fat mass in healthy men and women.

You might feel warm or even sweat after eating spicy foods as a result of increased calorie burning.

Ask your doctor if such supplements are right for you, or simply add chili peppers or chili pepper flakes to your favorite meals!

Stand Up More

To burn additional calories throughout the day, consider standing up vs. sitting down whenever you have an opportunity to do so.

This can boost your body's metabolism more than you think, especially if you have a desk job.

A 180-pound man can expend 674 calories sitting for 8 hours at a desk, or expend 1,027 calories sitting for 4 hours plus standing for 4 hours.

Consider getting a sit/stand desk at work to increase time spent standing down.

If you do sit for long time periods at work, break up the monotony by taking short walking or stair climbing breaks every hour or so.

Eat Full-Fat Foods

Low-fat diets are a thing of the past, as full-fat foods (particularly full-fat dairy foods) can boost satiety and lower your risk of weight gain.

Full-fat foods are usually higher in calories than low-fat alternatives but because they boost satiety, you likely won't consume as much of them.

In fact, studies show that whole-fat dairy foods don't contribute to weight gain.

Researches found that dairy food consumption can boost lean body mass, reduce body fat, and lower your risk of heart disease, diabetes, and other chronic diseases.

Dairy fat also contains medium-chain triglycerides (MCTs), which are known metabolism boosters.

Steer clear of fat-free dairy foods in favor of dairy products containing at least some fat.

If you prefer, opt for dairy-free plant alternatives (such as protein-fortified almond milk).

Add healthy fats to foods naturally low in fat.

For example, dip fresh vegetables in hummus, add nut butter to fruit, cook with plant-based oils, or add avocado slices to soups, salads, and sandwiches!

Join a Men's Health Program

After knowing more about what causes slow metabolism and ways to speed it up, consider joining a men's health program, such as the Fit Father Project, designed for busy dads over 40.

Doing so gives you unlimited access to metabolism-boosting workouts, nutritious meal plans, health coaching support from medical experts, and much more!

In addition to learning what causes slow metabolism, try a Fit Father Project free meal plan and workout to optimize your journey toward better health!


Erin Coleman B.S. - Nutritional Science, R.D., L.D.

Writer at The Fit Father Project

Erin Coleman is a registered and licensed dietitian with over 15 years of freelance writing experience.

She graduated with her Bachelor of Science degree in nutritional science from the University of Wisconsin-Madison, and completed her dietetic internship at Viterbo University in La Crosse, Wisconsin.

Prior to beginning her career in medical content writing, Erin worked as Health Educator for the University of Wisconsin-Madison Department of Internal Medicine.

Her published work appears on hundreds of health and fitness websites, and she’s currently working on publishing her first book! Erin is a wife, and a Mom to two beautiful children.

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*Please know that weight loss results & health changes/improvements vary from individual to individual; you may not achieve similar results. Always consult with your doctor before making health decisions. This is not medical advice – simply very well-researched info on what causes slow metabolism.


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